Many signal processing problems can be solved by maximizing the fitness of a segmented model over all possible partitions of the data interval. This letter describes a simple but powerful algorithm that searches the exponentially large space of partitions of $N$ data points in time $O(N^2)$. The algorithm is guaranteed to find the exact global optimum, automatically determines the model order (the number of segments), has a convenient real-time mode, can be extended to higher dimensional data spaces, and solves a surprising variety of problems in signal detection and characterization, density estimation, cluster analysis and classification.

In the Friedmann Model of the universe, cosmologists assume that spacelike slices of the universe are Riemannian manifolds of constant sectional curvature. This assumption is justified via Schur’s Theorem by stating that the spacelike universe is locally isotropic. Here we define a Riemannian manifold as almost locally isotropic in a sense which allows both weak gravitational lensing in all directions and strong gravitational lensing in localized angular regions at most points. We then prove that such a manifold is Gromov Hausdorff close to a length space $Y$ which is a collection of space forms joined at discrete points. Within the paper we define a concept we call an “exponential length space” and prove that if such a space is locally isotropic then it is a space form.

The ratio between the proton and electron masses is shown to be close to the ratio between the strong and electromagnetic interaction coupling constants at Extremely Low Energy (ELE). Based on the experimental data, this relation has been extended for the weak and gravitational interactions, too. Thus, a mass relation has been found, according to which the rest mass of the Lightest Free Massive Stable Particle (LFMSP), acted upon by a particular interaction, is proportional to the coupling constant of the respective interaction at ELE. On the basis of this mass relation, the electron neutrino and graviton masses have been approximately estimated to 2.1×10^(-4) eV/c^2 and 2.3×10^(-34) eV/c^2, respectively. The last value is of the order of the magnitude of hbar*H/c^2, where H is the Hubble constant and hbar is the reduced Planck constant. It is worth noting that this value has been obtained by fundamental constants only, without consideration of any cosmological models.

The ratio between the proton and electron masses is shown to be close to the ratio between the strong and electromagnetic interaction coupling constants at Extremely Low Energy (ELE). Based on the experimental data, this relation has been extended for the weak and gravitational interactions, too. Thus, a mass relation has been found, according to which the rest mass of the Lightest Free Massive Stable Particle (LFMSP), acted upon by a particular interaction, is proportional to the coupling constant of the respective interaction at ELE. On the basis of this mass relation, the electron neutrino and graviton masses have been approximately estimated to 2.1×10^(-4) eV/c^2 and 2.3×10^(-34) eV/c^2, respectively. The last value is of the order of the magnitude of hbar*H/c^2, where H is the Hubble constant and hbar is the reduced Planck constant. It is worth noting that this value has been obtained by fundamental constants only, without consideration of any cosmological models.

A set of algebraic equations for the topological properties of space-time is derived, and used to extend general relativity into the Planck domain. A unique basis set of three-dimensional prime manifolds is constructed which consists of $S^3$, $S^1\times S^2$, and $T^3$. The action of a loop algebra on these prime manifolds yields topological invariants which constrain the dynamics of the four-dimensional space-time manifold. An extended formulation of Mach’s principle and Einstein’s equivalence of inertial and gravitational mass is proposed which leads to the correct classical limit of the theory. It is found that the vacuum possesses four topological degrees of freedom corresponding to a lattice of three-tori. This structure for the quantum foam naturally leads to gauge groups O(n) and SU(n) for the fields, a boundary condition for the universe, and an initial state characterized by local thermal equilibrium. The current observational estimate of the cosmological constant is reproduced without fine-tuning and found to be proportional to the number of macroscopic black holes. The black hole entropy follows immediately from the theory and the quantum corrections to its Schwarzschild horizon are computed.

The evolution of the electric and magnetic components in an effective Yang-Mills condensate dark energy model is investigated. If the electric field is dominant, the magnetic component disappears with the expansion of the Universe. The total YM condensate tracks the radiation in the earlier Universe, and later it becomes $w_y\sim-1$ thus is similar to the cosmological constant. So the cosmic coincidence problem can be avoided in this model. However, if the magnetic field is dominant, $w_y>1/3$ holds for all time, suggesting that it cannot be a candidate for the dark energy in this case.

We explore the prospects for Advanced LIGO to detect gravitational waves from neutron stars and stellar mass black holes spiraling into intermediate-mass ($M\sim 50 M_\odot$ to $350 M_\odot$) black holes. We estimate an event rate for such \emph{intermediate-mass-ratio inspirals} (IMRIs) of up to $\sim 10$–$30 \mathrm{yr}^{-1}$. Our numerical simulations show that if the central body is not a black hole but its metric is stationary, axisymmetric, reflection symmetric and asymptotically flat then the waves will likely be tri-periodic, as for a black hole. We report generalizations of a theorem due to Ryan (1995) which suggest that the evolutions of the waves’ three fundamental frequencies and of the complex amplitudes of their spectral components encode (in principle) a full map of the central body’s metric, full details of the energy and angular momentum exchange between the central body and the orbit, and the time-evolving orbital elements. We estimate that Advanced LIGO can measure or constrain deviations of the central body from a Kerr black hole with modest but interesting accuracy.

We explore the prospects for Advanced LIGO to detect gravitational waves from neutron stars and stellar mass black holes spiraling into intermediate-mass ($M\sim 50 M_\odot$ to $350 M_\odot$) black holes. We estimate an event rate for such \emph{intermediate-mass-ratio inspirals} (IMRIs) of up to $\sim 10$–$30 \mathrm{yr}^{-1}$. Our numerical simulations show that if the central body is not a black hole but its metric is stationary, axisymmetric, reflection symmetric and asymptotically flat then the waves will likely be tri-periodic, as for a black hole. We report generalizations of a theorem due to Ryan (1995) which suggest that the evolutions of the waves’ three fundamental frequencies and of the complex amplitudes of their spectral components encode (in principle) a full map of the central body’s metric, full details of the energy and angular momentum exchange between the central body and the orbit, and the time-evolving orbital elements. We estimate that Advanced LIGO can measure or constrain deviations of the central body from a Kerr black hole with modest but interesting accuracy.

We show that a flow (timelike congruence) in any type $B_{1}$ warped product spacetime is uniquely and algorithmically determined by the condition of zero flux. (Though restricted, these spaces include many cases of interest.) The flow is written out explicitly for canonical representations of the spacetimes. With the flow determined, we explore an inverse approach to Einstein’s equations where a phenomenological fluid interpretation of a spacetime follows directly from the metric irrespective of the choice of coordinates. This approach is pursued for fluids with anisotropic pressure and shear viscosity. In certain degenerate cases this interpretation is shown to be generically not unique. The framework developed allows the study of exact solutions in any frame without transformations. We provide a number of examples, in various coordinates, including spacetimes with and without unique interpretations. The results and algorithmic procedure developed are implemented as a computer algebra program called GRSource.

We observe strong correlations between the temporal properties of gamma ray bursts (GRBs) and their apparent peak brightness. The strongest effect (with a significance level of 10^{-6}) is the difference between the brightness distributions of simple bursts (dominated by a single smooth pulse) and complex bursts (consisting of overlapping pulses). The latter has a break at a peak flux of 1.5 ph/cm^2/s, while the distribution of simple bursts is smooth down to the BATSE threshold. We also observe brightness dependent variations in the shape of the average peak aligned time profile (ATP) of GRBs. The decaying slope of the ATP shows time dilation when comparing bright and dim bursts while the rising slope hardly changes. Both slopes of the ATP are deformed for weak bursts as compared to strong bursts. The interpretation of these effects is simple: a complex burst where a number of independent pulses overlap in time appears intrinsically stronger than a simple burst. Then the BATSE sample of complex bursts covers larger redshifts where some cosmological factor causes the break in the peak brightness distribution. This break could correspond to the peak in the star formation rate that was recently shown to occur at a redshift of z~1.5.

We have obtained UBVRI images with the Kitt Peak and Cerro Tololo 4-m telescopes and Mosaic cameras of seven dwarfs in (or near) the Local Group, all of which have known evidence of recent star formation: IC10, NGC 6822, WLM, Sextans B, Sextans A, Pegasus,and Phoenix. We construct color-magnitude diagrams (CMDs) of these systems, as well as neighboring regions that can be used to evaluate the degree of foreground contamination by stars in the Milky Way. Inter-comparison of these CMDs with those of M31, M33, the LMC, and the SMC permits us to determine improved reddening values for a typical OB star found within these galaxies. All of the CMDs reveal a strong or modest number of blue supergiants. All but Pegasus and Phoenix also show the clear presence of red supergiants in the CMD, although IC10 appears to be deficient in these objects given its large WR population. The bright stars of intermediate color in the CMD are badly contaminated by foreground stars (30-100%), and considerable spectroscopy is needed before statistics on the yellow supergiants in these systems will be known. This study is intended to serve both as the impetus and “finding charts” for further space-based imaging, and for many spectroscopic programs at large aperture.

We investigate the star cluster population in the outer parts of the starburst galaxy NGC 5253 using archive images taken with the Hubble Space Telescope’s Advanced Camera for Surveys. Based on the F415W, F555W, and F814W photometry ages and masses are estimated for bona-fide star cluster candidates. We find three potentially massive ($\ge 10 \time 10^5$ \Msun) star clusters at ages of order of 1-2 Gyr, implying, if confirmed, a high global star formation rate in NGC 5253 during that epoch. This result underlines earlier findings that the current star burst is just one episode in an very active dwarf galaxy.

In this work the role of extra dimensions in the accelerated universe through the scenario of higher-dimensional Friedmann-Robertson-Walker (FRW) cosmology has been studied. For this purpose, we first consider warped space-time in the standard flat brane scenario as the modified form of Robertson-Walker (RW) metric in five-dimension (5D) space-time and then the variation of the bulk scale factor (warp factor), with respect to both space-like and time-like extra dimensions is obtained. Finally, it is shown that both of two types of extra dimensions are important in this scenario and also the bulk scale factor plays two different roles.

In this paper we present two concrete models of non-perfect fluid with bulk viscosity to interpret the observed cosmic accelerating expansion phenomena, avoiding the introduction of exotic dark energy. The first model we inspect has a viscosity of the form ${\zeta} = {\zeta}_0 + ({\zeta}_1-{\zeta}_2q)H$ by taking into account of the decelerating parameter q, and the other model is of the form ${\zeta} = {\zeta}_0 + {\zeta}_1H + {\zeta}_2H^2$. We give out the exact solutions of such models and further constrain them with the latest Union2 data as well as the currently observed Hubble-parameter dataset (OHD), then we discuss the fate of universe evolution in these models, which confronts neither future singularity nor little/pseudo rip. From the resulting curves by best fittings we find a much more flexible evolution processing due to the presence of viscosity while being consistent with the observational data in the region of data fitting. With the bulk viscosity considered, a more realistic universe scenario is characterized comparable with the {\Lambda}CDM model but without introducing the mysterious dark energy.

We present spectroscopic observations and chemical abundances of 16 planetary nebulae (PNe) in the outer disk of M31. The [O III] 4363 line is detected in all objects, allowing a direct measurement of the nebular temperature essential for accurate abundance determinations. Our results show that the abundances in these M31 PNe display the same correlations and general behaviors as Type II PNe in the Milky Way Galaxy. We also calculate photoionization models to derive estimates of central star properties. From these we infer that our sample PNe, all near the peak of the Planetary Nebula Luminosity Function, originated from stars near 2 M_sun. Finally, under the assumption that these PNe are located in M31’s disk, we plot the oxygen abundance gradient, which appears shallower than the gradient in the Milky Way.

We search for the presence of substructure, a non-Gaussian, asymmetrical velocity distribution of galaxies, and large peculiar velocities of the main galaxies in galaxy clusters with at least 50 member galaxies, drawn from the SDSS DR8. We employ a number of 3D, 2D, and 1D tests to analyse the distribution of galaxies in clusters: 3D normal mixture modelling, the Dressler-Shectman test, the Anderson-Darling and Shapiro-Wilk tests and others. We find the peculiar velocities of the main galaxies, and use principal component analysis to characterise our results. More than 80% of the clusters in our sample have substructure according to 3D normal mixture modelling, the Dressler-Shectman (DS) test shows substructure in about 70% of the clusters. The median value of the peculiar velocities of the main galaxies in clusters is 206 km/s (41% of the rms velocity). The velocities of galaxies in more than 20% of the clusters show significant non-Gaussianity. While multidimensional normal mixture modelling is more sensitive than the DS test in resolving substructure in the sky distribution of cluster galaxies, the DS test determines better substructure expressed as tails in the velocity distribution of galaxies. Richer, larger, and more luminous clusters have larger amount of substructure and larger (compared to the rms velocity) peculiar velocities of the main galaxies. Principal component analysis of both the substructure indicators and the physical parameters of clusters shows that galaxy clusters are complicated objects, the properties of which cannot be explained with a small number of parameters or delimited by one single test. The presence of substructure, the non-Gaussian velocity distributions, as well as the large peculiar velocities of the main galaxies, shows that most of the clusters in our sample are dynamically young.

The cosmic microwave background (CMB) power spectrum is a powerful cosmological probe as it entails almost all the statistical information of the CMB perturbations. Having access to only one sky, the CMB power spectrum measured by our experiments is only a realization of the true underlying angular power spectrum. In this paper we aim to recover the true underlying CMB power spectrum from the one realization that we have without a need to know the cosmological parameters. The sparsity of the CMB power spectrum is first investigated in two dictionaries; Discrete Cosine Transform (DCT) and Wavelet Transform (WT). The CMB power spectrum can be recovered with only a few percentage of the coefficients in both of these dictionaries and hence is very compressible in these dictionaries. We study the performance of these dictionaries in smoothing a set of simulated power spectra. Based on this, we develop a technique that estimates the true underlying CMB power spectrum from data, i.e. without a need to know the cosmological parameters. This smooth estimated spectrum can be used to simulate CMB maps with similar properties to the true CMB simulations with the correct cosmological parameters. This allows us to make Monte Carlo simulations in a given project, without having to know the cosmological parameters. The developed IDL code, TOUSI, for Theoretical pOwer spectrUm using Sparse estImation, will be released with the next version of ISAP.

The Fisher information matrix of the cosmic microwave background (CMB) radiation power spectrum coefficients is a fundamental quantity that specifies the information content of a CMB experiment. In the most general case, its exact calculation scales with the third power of the number of data points N and is therefore computationally prohibitive for state-of-the-art surveys. In this letter, we show how to compute the Fisher matrix in only O(N^2 log N) operations for a very large class of CMB experiments without special symmetries, as long as the inverse noise covariance matrix can be applied to a data vector in time O(l_max^3 log l_max}. This is true to a good approximation for all CMB data sets taken so far. The method takes into account common systematics such as arbitrary sky coverage and realistic noise correlations. As a consequence, optimal quadratic power spectrum estimation also becomes feasible in O(N^2 log N) operations for this large class of experiments. We discuss the relevance of our findings to other areas of cosmology where optimal power spectrum estimation plays a role.

We perform a fully relativistic analysis of odd-type linear perturbations around a static and spherically symmetric solution in the most general scalar-tensor theory with second-order field equations. It is shown that, as in the case of general relativity, the quadratic action for the perturbations reduces to the one having only a single dynamical variable, from which concise formulas for no-ghost and no-gradient instability conditions are derived. Our result is applicable to all the theories of gravity with an extra scalar degree of freedom. We demonstrate how the generic formulas can be applied to some particular examples such as the Brans-Dicke theory, $f(R)$ models, and Galileon gravity.

We study non-Gaussian properties of the isocurvature perturbations in the dark radiation, which consists of the active neutrinos and extra light species, if exist. We first derive expressions for the bispectra of primordial perturbations which are mixtures of curvature and dark radiation isocurvature perturbations. We also discuss CMB bispectra produced in our model and forecast CMB constraints on the nonlinearity parameters based on the Fisher matrix analysis. Some concrete particle physics motivated models are presented in which large isocurvature perturbations in extra light species and/or the neutrino density isocurvature perturbations as well as their non-Gaussianities may be generated. Thus detections of non-Gaussianity in the dark radiation isocurvature perturbation will give us an opportunity to identify the origin of extra light species and lepton asymmetry.

A new type of fluid matter model in general relativity is introduced, in which the fluid particles are subject to velocity diffusion without friction. In order to compensate for the energy lost by the fluid particles due to diffusion, a cosmological scalar field term is added to the left hand side of the Einstein equations. This hypothesis promotes diffusion to a new mechanism for accelerated expansion in cosmology. It is shown that diffusion alters not only quantitatively, but also qualitatively the global dynamical properties of the standard cosmological models.

We summarize the principles and fundamental ingredients of evolutionary synthesis models, which are stellar evolution, stellar atmospheres, the IMF, star-formation histories, nebular emission, and also attenuation from the ISM and IGM. The chapter focusses in particular on issues of importance for predictions of metal-poor and Population III dominated galaxies. We review recent predictions for the main physical properties and related observables of star-forming galaxies based on up-to-date inputs. The predicted metallicity dependence of these quantities and their physical causes are discussed. The predicted observables include in particular the restframe UV-to-optical domain with continuum emission from stars and the ionized ISM, as well as emission lines from H, He, and metals. Based on these predictions we summarize the main observational signatures (emission line strengths, colors etc.), which can be used to distinguish “normal” stellar populations from very metal-poor objects or even Pop III. Evolutionary synthesis models provide an important and fundamental tool for studies of galaxy formation and evolution, from the nearby Universe back to first galaxies. They are used in many applications to interpret existing observations, to predict and guide future missions/instruments, and to allow direct comparisons between state-of-the-art galaxy simulations and observations.

We present very early UV to optical photometric and spectroscopic observations of the peculiar Type IIn supernova (SN) 2011ht in UGC 5460. The UV observations of the rise to peak are only the second ever recorded for a Type IIn SN and are by far the most complete. The SN, first classified as a SN impostor, slowly rose to a peak of M_V \sim -17 in \sim55 days. In contrast to the \sim2 magnitude increase in the v-band light curve from the first observation until peak, the UV flux increased by >7 magnitudes. The optical spectra are dominated by strong, Balmer emission with narrow peaks (FWHM\sim600 km/s), very broad asymmetric wings (FWHM\sim4200 km/s), and blue shifted absorption (\sim300 km/s) superposed on a strong blue continuum. The UV spectra are dominated by FeII, MgII, SiII, and SiIII absorption lines broadened by \sim1500 km/s. Merged X-ray observations reveal a L_(0.2-10)=(1.0+/-0.2)x10^(39) erg/s. Some properties of SN 2011ht are similar to SN impostors, while others are comparable to Type IIn SNe. Early spectra showed features typical of luminous blue variables at maximum and during giant eruptions. However, the broad emission profiles coupled with the strong UV flux have not been observed in previous SN impostors. The absolute magnitude and energetics (~2.5×10^(49) ergs in the first 112 days) are reminiscent of normal Type IIn SN, but the spectra are of a dense wind. We suggest that the mechanism for creating this unusual profile could be a shock interacting with a shell of material that was ejected a year before the discovery of the SN.

By introducing Crossing functions and hyper-parameters I show that the Bayesian interpretation of the Crossing Statistics [1] can be used trivially for the purpose of model selection among cosmological models. In this approach to falsify a cosmological model there is no need to compare it with other models or assume any particular form of parametrization for the cosmological quantities like luminosity distance, Hubble parameter or equation of state of dark energy. Instead, hyper-parameters of Crossing functions perform as discriminators between correct and wrong models. Using this approach one can falsify any assumed cosmological model without putting priors on the underlying actual model of the universe and its parameters, hence the issue of dark energy parametrization is resolved. It will be also shown that the sensitivity of the method to the intrinsic dispersion of the data is small that is another important characteristic of the method in testing cosmological models dealing with data with high uncertainties.

We present an X-ray follow-up, based on XMM plus Chandra, of six Fossil Group (FG) candidates identified in our previous work using SDSS and RASS data. Four candidates (out of six) exhibit extended X-ray emission, confirming them as true FGs. For the other two groups, the RASS emission has its origin as either an optically dull/X-ray bright AGN, or the blending of distinct X-ray sources. Using SDSS-DR7 data, we confirm, for all groups, the presence of an r-band magnitude gap between the seed elliptical and the second-rank galaxy. However, the gap value depends, up to 0.5mag, on how one estimates the seed galaxy total flux, which is greatly underestimated when using SDSS (relative to Sersic) magnitudes. This implies that many FGs may be actually missed when using SDSS data, a fact that should be carefully taken into account when comparing the observed number densities of FGs to the expectations from cosmological simulations. The similarity in the properties of seed–FG and non-fossil ellipticals, found in our previous study, extends to the sample of X-ray confirmed FGs, indicating that bright ellipticals in FGs do not represent a distinct population of galaxies. For one system, we also find that the velocity distribution of faint galaxies is bimodal, possibly showing that the system formed through the merging of two groups. This undermines the idea that all selected FGs form a population of true fossils.

We probe the HI properties and the gas environments of three early-type barred galaxies harbouring counter-rotating ionized gas, NGC 128, NGC 3203 and NGC 7332. Each system has one or more optically-identified galaxy, at a similar or as yet unknown redshift within a 50 kpc projected radius. Using HI synthesis imaging data, we investigate the hypothesis that the counter-rotating gas in these galaxies has been accreted from their neighbours. In NGC 128 and NGC 3203, we find 9.6e7 and 2.3e8 Msun of HI, respectively, covering almost the entire stellar bodies of dwarf companions that appear physically connected. Both the HI morphology and kinematics are suggestive of tidal interactions. In NGC 7332, we do not find any directly-associated HI. Instead, NGC 7339, a neighbour of a comparable size at about 10 kpc, is found with 8.9e8 Msun of HI gas. More recently in a single dish observation, however, another group discovered a large HI structure which seems to be an extension of NGC 7339’s HI disc and also covers NGC 7332. All these observations thus suggest that HI gas is being accreted in these three galaxies from their companions, which is likely responsible for the kinematically-decoupled gas component present in their central region. Considering the incompleteness of existing studies of the faint dwarf galaxy population both in the optical and in HI, accretion from cold gas blobs, presumably gas-rich dwarfs, is expected to occur even more frequently than what is inferred from such cases that have been observed to date.

Using high spatial resolution HST WFC3 and ACS imaging of resolved stellar populations, we constrain the contribution of thermally-pulsing asymptotic giant branch (TP-AGB) stars and red helium burning (RHeB) stars to the 1.6 um near-infrared (NIR) luminosities of 23 nearby galaxies. The TP-AGB phase contributes as much as 17% of the integrated F160W flux, even when the red giant branch is well populated. The RHeB population contribution can match or even exceed the TP-AGB contribution, providing as much as 21% of the integrated F160W light. The NIR mass-to-light (M/L) ratio should therefore be expected to vary significantly due to fluctuations in the star formation rate over timescales from 25 Myr to several Gyr. We compare our observational results to predictions based on optically derived star formation histories and stellar population synthesis (SPS) models, including models based on the Padova isochrones (used in popular SPS programs). The SPS models generally reproduce the expected numbers of TP-AGB stars in the sample. The same SPS models, however, give a larger discrepancy in the F160W flux contribution from the TP-AGB stars, over-predicting the flux by a weighted mean factor of 2.3 +/-0.8. This larger offset is driven by the prediction of modest numbers of high luminosity TP-AGB stars at young (<300 Myrs) ages. The best-fit SPS models simultaneously tend to under-predict the numbers and fluxes of stars on the RHeB sequence, typically by a factor of 2.0+/-0.6 for galaxies with significant numbers of RHeBs. Coincidentally, over-prediction of the TP-AGB and under-prediction of the RHeBs result in a NIR M/L ratio largely unchanged for a rapid star formation rate. However, the NIR-to-optical flux ratio of galaxies could be significantly smaller than AGB-rich models would predict, an outcome that has been observed in some intermediate redshift post-starburst galaxies. (Abridged)

We present a simple, redshift-independent analytic model that explains the local Fundamental Metallicity Relation (FMR), taking into account the physical processes of star formation, inflow of metal-poor intergalactic medium (IGM) gas, and the outflow of metal rich interstellar medium (ISM) gas. We show that the physics of the FMR can be summarised as follows: for massive galaxies with stellar mass larger than 10^11 solar masses, ISM metal enrichment due to star formation is compensated by inflow of metal poor IGM gas, leading to a constant value of the gas metallicity with star formation rate (SFR); outflows are rendered negligible as a result of the large potential wells of these galaxies. On the other hand, as a result of their smaller SFR, less massive galaxies produce less heavy elements that are also more efficiently ejected due to their shallow potential wells; as a result, for a given stellar mass, the gas metallicity decreases with SFR. For such galaxies, the outflow efficiency determines both the slope, and the knee of the metallicity-SFR relation. The model is then successfully matched to results from numerical simulations including metal enrichment and feedback at higher redshifts.

We study the evolution of the red galaxy fraction (f_red) in 905 galaxy groups with 0.15 < z 2. In general, groups at lower redshifts exhibit larger f_red than those at higher redshifts, showing a group Butcher-Oemler effect. We investigate the evolution of f_red by examining its dependence on four parameters, which can be classified as one intrinsic and three environmental: galaxy stellar mass (M_*), total group stellar mass(M_{*,grp}, a proxy for group halo mass), normalized group-centric radius (r_grp), and local galaxy density (Sigma_5). We find that M_* is the dominant parameter such that there is a strong correlation between f_red and galaxy stellar mass. Furthermore, the dependence of f_red on the environmental parameters is also a strong function of M_*. Massive galaxies (M_* > 10^11 M_sun) show little dependence of f_red on r_grp, M_{*,grp}, and Sigma_5 over the redshift range. The dependence of f_red on these parameters is primarily seen for galaxies with lower masses, especially for M_* < 10^{10.6} M_{sun}. We observe an apparent `group down-sizing' effect, in that galaxies in lower-mass halos, after controlling for galaxy stellar mass, have lower f_red. We find a dependence of \fred on both \rgrp and \SigmaF after the other parameters are controlled. At a fixed \rgrp, there is a significant dependence of f_red on Sigma_5, while r_grp gradients of f_red are seen for galaxies in similar Sigma_5 regions. This indicates …..

One component of a massive black hole binary (MBHB) might capture a small third body, and then a hierarchical, inclined triple system would be formed. With the post-Newtonian approximation including radiation reaction, we analyzed the evolution of the triple initially with small eccentricities. We found that an essentially new resonant relation could arise in the triple system. Here relativistic effects are crucial. Relativistic resonances, including the new one, stably work even for an outer MBHB of comparable masses, and significantly change the orbit of the inner small body.

(abridged) We present a new analysis of a large sample of quasar absorption-line spectra obtained using UVES (the Ultraviolet and Visual Echelle Spectrograph) on the VLT (Very Large Telescope) in Chile. In the VLT sample (154 absorbers), we find evidence that alpha increases with increasing cosmological distance from Earth. However, as previously shown, the Keck sample (141 absorbers) provided evidence for a smaller alpha in the distant absorption clouds. Upon combining the samples an apparent variation of alpha across the sky emerges which is well represented by an angular dipole model pointing in the direction RA=(17.3 +/- 1.0) hr, dec. = (-61 +/- 10) deg, with amplitude (0.97 +0.22/-0.20) x 10^(-5). The dipole model is required at the 4.1 sigma statistical significance level over a simple monopole model where alpha is the same across the sky (but possibly different to the current laboratory value). The data sets reveal a number of remarkable consistencies: various data cuts are consistent and there is consistency in the overlap region of the Keck and VLT samples. Assuming a dipole-only (i.e. no-monopole) model whose amplitude grows proportionally with `lookback-time distance’ (r=ct, where t is the lookback time), the amplitude is (1.1 +/- 0.2) x 10^(-6) GLyr^(-1) and the model is significant at the 4.2 sigma confidence level over the null model [Delta alpha]/alpha = 0). We apply robustness checks and demonstrate that the dipole effect does not originate from a small subset of the absorbers or spectra. We present an analysis of systematic effects, and are unable to identify any single systematic effect which can emulate the observed variation in alpha.

Residual-gas expulsion after cluster formation has recently been shown to leave an imprint in the low-mass present-day stellar mass function (PDMF) which allowed the estimation of birth conditions of some Galactic globular clusters (GCs) such as mass, radius and star formation efficiency. We show that in order to explain their characteristics (masses, radii, metallicity, PDMF) their stellar initial mass function (IMF) must have been top-heavy. It is found that the IMF is required to become more top-heavy the lower the cluster metallicity and the larger the pre-GC cloud-core density are. The deduced trends are in qualitative agreement with theoretical expectation. The results are consistent with estimates of the shape of the high-mass end of the IMF in the Arches cluster, Westerlund 1, R136 and NGC 3603, as well as with the IMF independently constrained for ultra-compact dwarf galaxies (UCDs). The latter suggests that GCs and UCDs might have formed along the same channel or that UCDs formed via mergers of GCs. A fundamental plane is found which describes the variation of the IMF with density and metallicity of the pre-GC cloud-cores simultaneously. The implications for the evolution of galaxies and chemical enrichment over cosmological times are expected to be major.

Accretion onto supermassive black holes (SMBHs) in galaxy formation simulations is frequently modelled by the Bondi-Hoyle formalism. Here we examine the validity of this approach analytically and numerically. We argue that the character of the flow where one evaluates the gas properties is unlikely to satisfy the simple Bondi-Hoyle model. Only in the specific case of hot virialised gas with zero angular momentum and negligible radiative cooling is the Bondi-Hoyle solution relevant. In the opposite extreme, where the gas is in a state of free-fall at the evaluation radius due to efficient cooling and the dominant gravity of the surrounding halo, the Bondi-Hoyle formalism can be erroneous by orders of magnitude in either direction. This may impose artificial trends with halo mass in cosmological simulations by being wrong by different factors for different halo masses. We propose an expression for the sub-grid accretion rate which interpolates between the free-fall regime and the Bondi-Hoyle regime, therefore taking account of the contribution of the halo to the gas dynamics.

Model independent reconstructions of dark energy have received some attention. The approach that addresses the reconstruction of the dimensionless coordinate distance and its two first derivatives using a polynomial fit in different redshift windows is well developed \cite{DalyDjorgovski1,DalyDjorgovski2,DalyDjorgovski3}. In this work we offer new insights into the problem by focusing on two types of observational probes: SNeIa and GRBs. Our results allow to highlight some of the intrinsic weaknesses of the method. One of the directions we follow is to consider updated observational samples. Our results indicate than conclusions on the main dark energy features as drawn from this method are intimately related to the features of the samples themselves (which are not quite ideal). This is particularly true of GRBs, which manifest themselves as poor performers in this context. In contrast to original works, we conclude they cannot be used for cosmological purposes, and the state of the art does not allow to regard them on the same quality basis as SNeIa. The next direction we contribute to is the question of how the adjusting of some parameters (window width, overlap, selection criteria) affect the results. We find again there is a considerable sensitivity to these features. Then, we try to establish what is the current redshift range for which one can make solid predictions on dark energy evolution. Finally, we strengthen the former view that this model is modest in the sense it provides only a picture of the global trend. But, on the other hand, we believe it offers an interesting complement to other approaches given that it works on minimal assumptions.

An integral part of the Unified Model for Active Galactic Nuclei (AGNs) is an axisymmetric obscuring medium, which is commonly depicted as a torus of gas and dust surrounding the central engine. However, a robust, dynamical model of the torus is required in order to understand the fundamental physics of AGNs and interpret their observational signatures. Here we explore self-similar, dusty disk-winds, driven by both magnetocentrifugal forces and radiation pressure, as an explanation for the torus. Using these models, we make predictions of AGN infrared (IR) spectral energy distributions (SEDs) from 2-100 microns by varying parameters such as: the viewing angle; the base column density of the wind; the Eddington ratio; the black hole mass; and the amount of power in the input spectrum emitted in the X-ray relative to that emitted in the UV/optical. We find that models with N_H,0 = 10^25 cm^-2, L/L_Edd = 0.1, and M_BH >= 10^8 Msun are able to adequately approximate the general shape and amount of power expected in the IR as observed in a composite of optically luminous Sloan Digital Sky Survey (SDSS) quasars. The effect of varying the relative power coming out in X-rays relative to the UV is a change in the emission below ~5 micron from the hottest dust grains; this arises from the differing contributions to heating and acceleration of UV and X-ray photons. We see mass outflows ranging from ~1-4 Msun/yr, terminal velocities ranging from ~1900-8000 km/s, and kinetic luminosities ranging from ~1×10^42-8×10^43 erg/s. Further development of this model holds promise for using specific features of observed IR spectra in AGNs to infer fundamental physical parameters of the systems.

In this paper we measure the merger fraction and rate, both minor and major, of massive early-type galaxies (M_star >= 10^11 M_Sun) in the COSMOS field, and study their role in mass and size evolution. We use the 30-band photometric catalogue in COSMOS, complemented with the spectroscopy of the zCOSMOS survey, to define close pairs with a separation 10h^-1 kpc <= r_p <= 30h-1 kpc and a relative velocity Delta v = 1/4) and minor (1/10 <= mu = 1/10 mergers can explain ~55% of the observed size evolution of these galaxies since z ~ 1. Another ~20% is due to the progenitor bias (younger galaxies are more extended) and we estimate that very minor mergers (mu < 1/10) could contribute with an extra ~20%. The remaining ~5% should come from other processes (e.g., adiabatic expansion or observational effects). This picture also reproduces the mass growth and velocity dispersion evolution of these galaxies. We conclude from these results that merging is the main contributor to the size evolution of massive ETGs at z <= 1, accounting for ~50-75% of that evolution in the last 8 Gyr. Nearly half of the evolution due to mergers is related to minor (mu < 1/4) events.

We provide an overview of ancillary 24, 70, and 160 micron data from the Multiband Imaging Photometer for Spitzer (MIPS) that are intended to complement the 70-500 micron Herschel Space Observatory photometry data for nearby galaxies obtained by the Herschel-SPIRE Local Galaxies Guaranteed Time Programs and the Herschel Virgo Cluster Survey. The MIPS data can be used to extend the photometry to wave bands that are not observed in these Herschel surveys and to check the photometry in cases where Herschel performs observations at the same wavelengths. Additionally, we measured globally-integrated 24-160 micron flux densities for the galaxies in the sample that can be used for the construction of spectral energy distributions. Using MIPS photometry published by other references, we have confirmed that we are obtaining accurate photometry for these galaxies.

A generic feature of the known string inflationary models is that the same physics that makes the inflaton lighter than the Hubble scale during inflation often also makes other scalars this light. These scalars can acquire isocurvature fluctuations during inflation, and given that their VEVs determine the mass spectrum and the coupling constants of the effective low-energy field theory, these fluctuations give rise to couplings and masses that are modulated from one Hubble patch to another. These seem just what is required to obtain primordial adiabatic fluctuations through conversion into density perturbations through the `modulation mechanism’, wherein reheating takes place with different efficiency in different regions of our Universe. Fluctuations generated in this way can generically produce non-gaussianity larger than obtained in single-field slow-roll inflation; potentially observable in the near future. We provide here the first explicit example of the modulation mechanism at work in string cosmology, within the framework of LARGE Volume Type-IIB string flux compactifications. The inflationary dynamics involves two light Kaehler moduli: a fibre divisor plays the role of the inflaton whose decay rate to visible sector degrees of freedom is modulated by the primordial fluctuations of a blow-up mode (which is made light by the use of poly-instanton corrections). We find the challenges of embedding the mechanism into a concrete UV completion constrains the properties of the non-gaussianity that is found, since for generic values of the underlying parameters, the model predicts a local bi-spectrum with fNL of order `a few’. However, a moderate tuning of the parameters gives also rise to explicit examples with fNL O(20) potentially observable by the Planck satellite.

Mrk938 is a luminous infrared galaxy in the local Universe believed to be the remnant of a galaxy merger. It shows a Seyfert 2 nucleus and intense star formation according to optical spectroscopic observations. We have studied this galaxy using new Herschel far-IR imaging data in addition to archival X-ray, UV, optical, near-IR and mid-IR data. Mid- and far-IR data are crucial to characterise the starburst contribution, allowing us to shed new light on its nature and to study the coexistence of AGN and starburst activity in the local Universe. The decomposition of the mid-IR Spitzer spectrum shows that the AGN bolometric contribution to the mid-IR and total infrared luminosity is small (Lbol(AGN)/LIR~0.02), which agrees with previous estimations. We have characterised the physical nature of its strong infrared emission and constrained it to a relatively compact emitting region of <2kpc. It is in this obscured region where most of the current star formation activity is taking place as expected for LIRGs. We have used Herschel imaging data for the first time to constrain the cold dust emission with unprecedented accuracy. We have fitted the integrated far-IR spectral energy distribution and derived the properties of the dust, obtaining a dust mass of 3×10^7Msun. The far-IR is dominated by emission at 35K, consistent with dust heated by the on-going star formation activity.

It is well known that the vacuum in the Einstein gravity, which is linear in the Riemann curvature, is trivial in the critical (2+1=3) dimension because vacuum solution is flat. It turns out that this is true in general for any odd critical $d=2n+1$ dimension where $n$ is the degree of homogeneous polynomial in Riemann defining its higher order analogue whose trace is the nth order Lovelock polynomial. This is the “curvature” for nth order pure Lovelock gravity as the trace of its Bianchi derivative gives the corresponding analogue of the Einstein tensor \cite{bianchi}. Thus the vacuum in the pure Lovelock gravity is always trivial in the odd critical (2n+1) dimension which means it is pure Lovelock flat but it is not Riemann flat unless $n=1$ and then it describes a field of a global monopole. Further by adding Lambda we obtain the Lovelock analogue of the BTZ black hole.

The first dedicated search for ultra-high energy (UHE) tau neutrinos of astrophysical origin was performed using the IceCube detector in its 22-string configuration. The search also had sensitivity to UHE electron and muon neutrinos. After application of all selection criteria to approximately 200 live-days of data, we expect a background of 0.60 +/- 0.19 (stat.) $^{+0.56}_{-0.58}$ (sys.) events and observe three events, which after inspection emerge as being compatible with background. Therefore, we set an upper limit on neutrinos of all flavors from UHE astrophysical sources at 90% CL of $E^{2} \Phi(\nu_{x}) < 16.2 * 10^-8 GeV cm^-2 sr^-1 s^-1 over an estimated primary neutrino energy range of 340 TeV to 200 PeV.

Here we summarize our recent results of high-resolution computer simulations on the turbulent amplification of weak magnetic seed fields showing that such fields will be exponentially amplified also during the gravitational collapse reminiscent to the situation during primordial star formation. The exponential magnetic field amplification is driven by the turbulent small-scale dynamo that can be only observed in computer simulations if the turbulent motions in the central core are sufficiently resolved. We find that the Jeans length, which determines the central core region, has to be resolved by at least 30 grid cells to capture the dynamo activity. We conclude from our studies that strong magnetic fields will be unavoidably created already during the formation of the first stars in the Universe, potentially influencing their evolution and mass distribution.

Based on the ATLBS survey we present a sample of extended radio sources and derive morphological properties of faint radio sources. 119 radio galaxies form the ATLBS-Extended Source Sample (ATLBS-ESS) consisting of all sources exceeding 30″ in extent and integrated flux densities exceeding 1 mJy. We give structural details along with information on galaxy identifications and source classifications. The ATLBS-ESS, unlike samples with higher flux-density limits, has almost equal fractions of FR-I and FR-II radio galaxies with a large fraction of the FR-I population exhibiting 3C31-type structures. Significant asymmetry in lobe extents appears to be a common occurrence in the ATLBS-ESS FR-I sources compared to FR-II sources. We present a sample of 22 FR-Is at z>0.5 with good structural information. The detection of several giant radio sources, with size exceeding 0.7 Mpc, at z>1 suggests that giant radio sources are not less common at high redshifts. The ESS also includes a sample of 28 restarted radio galaxies. The relative abundance of dying and restarting sources is indicative of a model where radio sources undergo episodic activity in which an active phase is followed by a brief dying phase that terminates with restarting of the central activity; in any massive elliptical a few such activity cycles wherein adjacent events blend may constitute the lifetime of a radio source and such bursts of blended activity cycles may be repeated over the age of the host. The ATLBS-ESS includes a 2-Mpc giant radio galaxy with the lowest surface brightness lobes known to date.

In General Relativity, the average velocity field of dark matter around galaxy clusters is uniquely determined by the mass profile. The latter can be measured through weak lensing. We propose a new method of measuring the velocity field (phase space density) by stacking redshifts of surrounding galaxies from a spectroscopic sample. In combination with lensing, this yields a direct test of gravity on scales of 1-30 Mpc. Using N-body simulations, we show that this method can improve upon current constraints by several orders of magnitude when applied to upcoming imaging and redshift surveys.

We present a statistical study of the environments of 63 high-redshift radio galaxies (HzRGs) between redshifts 1<z<5.2, using the 24um, waveband of the MIPS instrument aboard the Spitzer Space Telescope. Using a counts-in-cell analysis, a statistically significant source overdensity is found in 1.75arcmin radius circular cells centred on the HzRGs when compared to reference fields. We report an average overdensity of delta (= {N}_{targets} / {N}_{reference}) = 2.2 +/- 1.2 at a flux density cut of f24um=0.3mJy. This result implies that HzRGs are likely to lie in protoclusters of active and star-forming galaxies at high redshift. Over 95% of our targeted HzRGs lie in higher than average density fields. Further, 20 (32%) of our selected fields are found to be overdense to at least a 3sigma significance, of which 9 are newly identified protocluster candidates. We observe a weak correlation between redshift and 24um, source density, and discuss the populations being probed at different redshifts. In our uniformly selected sample, which was designed to cover two orders of magnitude in radio luminosity throughout z=1-4, we find that the 24um, source density does not depend on radio luminosity. We also compare this result with recent work describing IRAC source overdensities around the same HzRGs and find correlations between the results.

Taking advantage of the impressive sensitivity of Spitzer to detect massive galaxies at high redshift, we study the mid-infrared environments of powerful, high-redshift radio galaxies at 1.2<z-0.1 (AB), in the fields of 48 radio galaxies at 1.2<z1.2. Using a counts-in-cell analysis, we identify a field as overdense when 15 or more red IRAC sources are found within 1arcmin (i.e.,~0.5Mpc at 1.2<z1.2.

We present spectroscopic data for 180 red giant branch stars in the isolated dwarf irregular galaxy WLM. Observations of the Calcium II triplet lines in spectra of RGB stars covering the entire galaxy were obtained with FORS2 at the VLT and DEIMOS on Keck II allowing us to derive velocities, metallicities, and ages for the stars. With accompanying photometric and radio data we have measured the structural parameters of the stellar and gaseous populations over the full galaxy. The stellar populations show an intrinsically thick configuration with $0.39 \leq q_{0} \leq 0.57$. The stellar rotation in WLM is measured to be $17 \pm 1$ km s$^{-1}$, however the ratio of rotation to pressure support for the stars is $V/\sigma \sim 1$, in contrast to the gas whose ratio is seven times larger. This, along with the structural data and alignment of the kinematic and photometric axes, suggests we are viewing WLM as a highly inclined oblate spheroid. Stellar rotation curves, corrected for asymmetric drift, are used to compute a dynamical mass of $4.3\pm 0.3\times10^{8} $M$_{\odot}$ at the half light radius ($r_{h} = 1656 \pm 49$ pc). The stellar velocity dispersion increases with stellar age in a manner consistent with giant molecular cloud and substructure interactions producing the heating in WLM. Coupled with WLM’s isolation, this suggests that the extended vertical structure of its stellar and gaseous components and increase in stellar velocity dispersion with age are due to internal feedback, rather than tidally driven evolution. These represent some of the first observational results from an isolated Local Group dwarf galaxy which can offer important constraints on how strongly internal feedback and secular processes modulate SF and dynamical evolution in low mass isolated objects.

Fossil galaxy groups are spatially extended X-ray sources with X-ray luminosities above L_X,bol > 10^42 h_50^-2 ergs s^-1 and a central elliptical galaxy dominating the optical, the second-brightest galaxy being at least 2 magnitudes fainter in the R band. Whether these systems are a distinct class of objects resulting from exceptional formation and evolution histories is still unclear, mainly due to the small number of objects studied so far, mostly lacking spectroscopy of group members for group membership confirmation and a detailed kinematical analysis. To complement the scarce sample of spectroscopically studied fossils down to their faint galaxy populations, the fossil candidate RX J1548.9+0851 (z=0.072) is studied in this work. Our results are compared with existing data from fossils in the literature. We use ESO VLT VIMOS multi-object spectroscopy to determine redshifts of the faint galaxy population and study the luminosity-weighted dynamics and luminosity function of the system. The full-spectrum fitting package ULySS is used to determine ages and metallicities of group members. VIMOS imaging data are used to study the morphology of the central elliptical. We identify 40 group members spectroscopically within the central ~300 kpc of the system and find 31 additional redshifts from the literature, resulting in a total number of 54 spectroscopically confirmed group members within 1 Mpc. RX J1548.9+0851 is made up of two bright ellipticals in the central region with a magnitude gap of m_1,2 = 1.34 in the SDSS r’ band leaving the definition of RX J1548.9+0851 being a fossil to the assumption of the virial radius. We find a luminosity-weighted velocity dispersion of 568 km s^-1 and a mass of ~2.5 x 10^14 M_sun for the system confirming previous studies that revealed fossils to be massive. (abridged)

We use the Mitchell Spectrograph (formerly VIRUS-P) on the McDonald Observatory 2.7m Harlan J. Smith Telescope to search for the chemical signatures of massive elliptical galaxy assembly. The Mitchell Spectrograph is an integral-field spectrograph with a uniquely wide field of view (107×107 sq arcsec), allowing us to achieve remarkably high signal-to-noise ratios of ~20-70 per pixel in radial bins of 2-2.5 times the effective radii of the eight galaxies in our sample. Focusing on a sample of massive elliptical galaxies with stellar velocity dispersions sigma* > 150 km/s, we study the radial dependence in the equivalent widths (EWs) of key metal absorption lines. By twice the effective radius, the Mgb EWs have dropped by ~50%, and only a weak correlation between sigma* and Mgb EW remains. The Mgb EWs at large radii are comparable to those seen in the centers of elliptical galaxies that are approximately an order of magnitude less massive. We find that the well-known metallicity gradients often observed within an effective radius continue smoothly to 2.5R_e, while the abundance ratio gradients remain flat. Much like the halo of the Milky Way, the stellar halos of our galaxies have low metallicities and high alpha-abundance ratios, as expected for very old stars formed in small stellar systems. Our observations support a picture in which the outer parts of massive elliptical galaxies are built by the accretion of much smaller systems whose star formation history was truncated at early times.

We report the outcome of a 3-day workshop on the Hubble constant (H_0) that took place during February 6-8 2012 at the Kavli Institute for Particle Astrophysics and Cosmology, on the campus of Stanford University. The participants met to address the following questions. Are there compelling scientific reasons to obtain more precise and more accurate measurements of H_0 than currently available? If there are, how can we achieve this goal? The answers that emerged from the workshop are (1) better measurements of H_0 provide critical independent constraints on dark energy, spatial curvature of the Universe, neutrino physics, and validity of general relativity, (2) a measurement of H_0 to 1% in both precision and accuracy, supported by rigorous error budgets, is within reach for several methods, and (3) multiple paths to independent determinations of H_0 are needed in order to access and control systematics.

Galaxy clusters provide us with important information about the cosmology of our universe. Observations of the X-ray radiation or of the SZ effect allow us to measure the density and temperature of the hot intergalactic medium between the galaxies in a cluster, which then allow us to calculate the total mass of the galaxy cluster. However, no simple connection between the density and the temperature profiles has been identified. Here we use controlled high-resolution numerical simulations to identify a relation between the density and temperature of the gas in equilibrated galaxy clusters. We demonstrate that the temperature-density relation is a real attractor, by showing that a wide range of equilibrated structures all move towards the attractor when perturbed and subsequently allowed to relax. For structures which have undergone sufficient perturbations for this connection to hold, one can therefore extract the mass profile directly from the X-ray intensity profile.

Many haloes of nearby disc galaxies contain faint and extended features, including loops, which are often interpreted as relics of satellite infall in the main galaxy’s potential well. In most cases, however, the residual nucleus of the satellite is not seen, although it is predicted by numerical simulations. We test whether such faint and extended features can be associated to gas-rich, major mergers, which may also lead to disc rebuilding and thus be a corner stone for the formation of spiral galaxies. Using the TreeSPH code GADGET-2, we model the formation of an almost bulge-less galaxy similar to NGC 5907 (B/T $\le$ 0.2) after a gas-rich major merger. We indeed find that 3:1 major mergers can form features similar to the loops found in many galactic haloes, including in NGC 5907, and can reproduce an extended thin disc, a bulge, as well as the pronounced warp of the gaseous disc. Even though it remains difficult to fully cover the large volume of free parameters, the present modelling of the loops in NGC 5907 proves that they could well be the result of a major merger. It has many advantages over the satellite infall scenario; e.g., it solves the problem of the visibility of the satellite remnant, and it may explain some additional features in the NGC 5907 halo, as well as some gas properties of this system. For orbital parameters derived from cosmological simulations, the loops in NGC 5907 can be reproduced by major mergers (3:1 to 5:1) and possibly by intermediate mergers (5:1 to 12:1). The major merger scenario thus challenges the minor merger one and could explain many properties that haloes of spiral galaxies have in common, including their red colours and the presence of faint extended features.

If the expansion of the early Universe was not purely de Sitter, the statistical imprints of the primordial density perturbation on the cosmic microwave background can be quite different from those following slow-roll inflation. In this paper we study the inflationary signatures of all single-field models not plagued by ghost-like instabilities. We assume small deviations from exact scale-invariance, as supported by current cosmological constraints, allow for a rapid change of the Hubble parameter and the phase speed of scalar fluctuations. We obtain the propagator of scalar fluctuations and compute the bispectrum, keeping next-order corrections proportional to the deviation of the spectral index from unity. These theories offer an explicit example where the shape and scale dependences of the bispectrum are highly non-trivial for reasonable breaking of slow-roll.

This paper presents both the result of a search for fossil systems within the XMM Cluster Survey and the Sloan Digital Sky Survey and the results of a study of the stellar mass assembly and stellar populations of their fossil galaxies. In total, 17 groups and clusters are identified at z < 0.25 with large magnitude gaps between the first and fourth brightest galaxies. All the information necessary to classify these systems as fossils is provided. For both groups and clusters, the total and fractional luminosity of the brightest galaxy are positively correlated with the magnitude gap. The brightest galaxies in fossil systems (called fossil galaxies) have stellar populations and star-formation histories which are similar to normal brightest cluster galaxies. However, at fixed group/cluster mass, the stellar masses of the fossil galaxies are larger compared to normal brightest cluster galaxies, a fact that holds true over a wide range of group/cluster masses. Moreover, the fossil galaxies are found to contain a significant fraction of the the total optical luminosity of the group/cluster within 0.5R200, as much as 85%, compared to the non-fossils, which can have as little as 10%. Our results suggest that fossil systems formed early and in the highest density regions of the Universe and that fossil galaxies represent the end products of galaxy mergers in groups and clusters.

We have mapped faint 1667 OH line emission (TA \approx 20 – 40 mK in our \approx 30′ beam) along many lines of sight in the Galaxy covering an area of \approx 4\circ \times 4\circ in the general direction of l \approx 108\circ, b \approx 5\circ. The OH emission is widespread, similar in extent to the local HI (r </= 2 kpc) both in space and in velocity. The OH profile amplitudes show a good general correlation with those of HI in spectral channels of \approx 1 km/s; this relation is described by TA(OH) \approx 1.50 \times 10^{-4} TB(HI) for values of TB(HI) </\approx 60 – 70 K. Beyond this the HI line appears to "saturate", and few values are recorded above \approx 90 K. However, the OH brightness continues to rise, by a further factor \approx 3. The OH velocity profiles show multiple features with widths typically 2 – 3 km/s, but less than 10% of these features are associated with CO(1-0) emission in existing surveys of the area smoothed to comparable resolution.

Quasars provide our farthest-reaching view of the Universe. The Sloan Survey now contains over 100,000 quasar candidates. A careful look at the angular distribution of quasar magnitudes shows a surprising intensity enhancement with a “bulls eye” pattern toward (alpha,delta) ~ (195{\deg}, 0{\deg}) for all wavelengths from UV through infrared. The angular pattern and size of the enhancement is very similar for all wavelengths, which is inconsistent with a Doppler shift due to a large peculiar velocity toward that direction. The shift is also too large to explain as a systematic error in the quasar magnitudes. The general features of the anomaly can be explained by the gravitational lensing of a massive bubble with Mlens ~ 10^21 M\odot, a lens radius ~350 Mpc, and with the lens subtending an angle of \pm15{\deg} on the sky. It is remarkable that the presence of such a massive bubble universe can explain not only the anomalies in the angular distribution of quasar intensities, but also anomalies in the distribution of luminous red galaxies, anomalies in the CMB, and bulk flow discrepancies, all of which appear in roughly the same direction.

We forecast the ability of future CMB and galaxy lensing surveys to constrain variations of the fine structure constant. We found that lensing data, as those expected from satellite experiments as Euclid could improve the constraint from future CMB experiments leading to a \Delta \alpha / \alpha = 8*10^{-4} accuracy. A variation of the fine structure constant \alpha is strongly degenerate with the Hubble constant H_0 and with inflationary parameters as the scalar spectral index n_s. These degeneracies may cause significant biases in the determination of cosmological parameters if a variation in \alpha as large as \sim 0.5 % is present at the epoch of recombination.

We forecast the ability of future CMB and galaxy lensing surveys to constrain variations of the fine structure constant. We found that lensing data, as those expected from satellite experiments as Euclid could improve the constraint from future CMB experiments leading to a \Delta \alpha / \alpha = 8*10^{-4} accuracy. A variation of the fine structure constant \alpha is strongly degenerate with the Hubble constant H_0 and with inflationary parameters as the scalar spectral index n_s. These degeneracies may cause significant biases in the determination of cosmological parameters if a variation in \alpha as large as \sim 0.5 % is present at the epoch of recombination.

We forecast the ability of future CMB and galaxy lensing surveys to constrain variations of the fine structure constant. We found that lensing data, as those expected from satellite experiments as Euclid could improve the constraint from future CMB experiments leading to a \Delta \alpha / \alpha = 8*10^{-4} accuracy. A variation of the fine structure constant \alpha is strongly degenerate with the Hubble constant H_0 and with inflationary parameters as the scalar spectral index n_s. These degeneracies may cause significant biases in the determination of cosmological parameters if a variation in \alpha as large as \sim 0.5 % is present at the epoch of recombination.

Precision measurements of nature’s fundamental couplings and a first measurement of the cosmological redshift drift are two of the key targets for future high-resolution ultra-stable spectrographs such as CODEX. Being able to do both gives CODEX a unique advantage, allowing it to probe dynamical dark energy models (by measuring the behavior of their equation of state) deep in the matter era and thereby testing classes of models that would otherwise be difficult to distinguish from the standard $\Lambda$CDM paradigm. We illustrate this point with two simple case studies.

In 2011, I published a popular-level book, The Fallacy of Fine-Tuning: Why the Universe is Not Designed for Us. It investigated a common claim found in contemporary religious literature that the parameters of physics and cosmology are so delicately balanced, so “fine-tuned,” that any slight change and life in the universe would have been impossible. I concluded that while the precise form of life we find on Earth would not exist with slight changes in these parameters, some form of life could have evolved over a parameter range that is not infinitesimal, as often claimed. Postdoctoral fellow Luke Barnes has written a lengthy, highly technical review [arXiv:1112.4647] of the scientific literature on the fine-tuning problem. I have no significant disagreement with that literature and no prominent physicist or cosmologist has disputed my basic conclusions. Barnes does not invalidate these conclusions and misunderstands and misrepresents much of what is in the book.

Search for the statistical anisotropy in the CMB data is a powerful tool for constraining models of the early Universe. In this paper we focus on the recently proposed cosmological scenario with conformal rolling. We consider two sub-scenarios, one of which involves a long intermediate stage between conformal rolling and conventional hot epoch. Primordial scalar perturbations generated within these sub-scenarios have different direction-dependent power spectra, both characterized by a single parameter h^2. We search for the signatures of this anisotropy in the seven-year WMAP data using quadratic maximum likelihood method, first applied for similar purposes by Hanson and Lewis. We confirm the large quadrupole anisotropy detected in V and W bands, which has been argued to originate from systematic effects rather than from cosmology. We construct an estimator for the parameter h^2. In the case of the sub-scenario with the intermediate stage we set an upper limit h^2 < 0.045 at the 95% confidence level. The constraint on h^2 is much weaker in the case of another sub-scenario, where the intermediate stage is absent.

Using Gemini North telescope ultra deep and high resolution (sub-kpc) K-band adaptive optics imaging of a sample of 4 nearby (z~0.15) massive (~10^{11}M_{sun}) compact (R<1.5 kpc) galaxies, we have explored the structural properties of these rare objects with an unprecedented detail. Our surface brightness profiles expand over 12 magnitudes in range, allowing us to explore the presence of any faint extended envelope on these objects down to stellar mass densities ~10^{6} M_{sun}/kpc^{2} at radial distances of ~15 kpc. We find no evidence for any extended faint tail altering the compactness of these galaxies. Our objects are elongated, resembling visually S0 galaxies and have a central stellar mass density well above the stellar mass densities of objects with similar stellar mass but normal size in the present universe. If these massive compact objects will eventually transform into normal size galaxies, the processes driving this size growth will have to migrate around 2-3×10^{10}M_{sun} stellar mass from their inner (R<1.7 kpc) region towards their outskirts. Nearby massive compact galaxies share with high-z compact massive galaxies not only their stellar mass, size and velocity dispersion but also the shape of their profiles and age of their stellar populations. This makes these singular galaxies unique laboratories to explore the early stages of the formation of massive galaxies.

We present the results of a study of observational and identification techniques used for surveys and spectroscopy of candidate supernova remnants (SNRs) in the Sculptor Group galaxy NGC 300. The goal of this study was to investigate the reliability of using [Sii]/Halpha > 0.4 in optical SNR surveys and spectra as an identifying feature of extra-galactic SNRs (egSNRs) and also to investigate the effectiveness of the observing techniques (which are hampered by seeing conditions and telescope pointing errors) using this criterion in egSNR surveys and spectrographs. This study is based on original observations of these objects and archival data obtained from the Hubble Space Telescope which contained images of some of the candidate SNRs in NGC 300. We found that the reliability of spectral techniques may be questionable and very high-resolution images may be needed to confirm a valid identification of some egSNRs.

We explore the equation of state (EoS) for dark energy $w_{\mathrm{DE}}$ in modified gravitational theories to explain the current accelerated expansion of the universe. We explicitly demonstrate that the future crossings of the phantom divide line of $w_{\mathrm{DE}}=-1$ are the generic feature in the existing viable $f(R)$ gravity models. Furthermore, we show that the crossing of the phantom divide can be realized in the combined $f(T)$ theory constructed with the exponential and logarithmic terms. In addition, we investigate the effective EoS for the universe when the finite-time future singularities occur in non-local gravity.

An anisotropic cosmic fluid with radial heat flux which sources a time dependent Rindler geometry is investigated. Even though its energy density $\rho$ is positive, the radial and transversal pressures are negative and the strong energy condition is not satisfied. The congruence of “static” observers is not geodesic and the heat flux is oriented outward. We computed the Misner-Sharp energy associated to the curved Rindler metric embedded in a spatially flat FLRW universe and found that the Weyl energy is vanishing thanks to the conformally flat form of the spacetime.

In the standard formulation of the smoothed particle hydrodynamics (SPH), it is assumed that the local density distribution is differentiable. This assumption is used to derive the spatial derivatives of other quantities. However, this assumption breaks down at the contact discontinuity, which appears often in simulations of astronomical objects. At the contact discontinuity, the density of the low-density side is overestimated while that of the high-density side is underestimated. As a result, the pressure of the low (high) density side is over (under) estimated. Thus, unphysical repulsive force appears at the contact discontinuity, resulting in the effective surface tension. This effective surface tension suppresses instabilities such as the Kelvin-Helmholtz and Rayleigh-Taylor instabilities. In this paper, we present a new formulation of SPH, which does not require the differentiability of density and thus can handle contact discontinuity without numerical problems. The results of standard tests such as the shock tube, Kelvin-Helmholtz and Rayleigh-Taylor instabilities, and the blob tests are all very favorable to our new formulation. We conclude that our new formulation solved practically all known difficulties of the standard SPH, without introducing additional numerical diffusion or breaking the exact force symmetry or energy conservation.

In the standard formulation of the smoothed particle hydrodynamics (SPH), it is assumed that the local density distribution is differentiable. This assumption is used to derive the spatial derivatives of other quantities. However, this assumption breaks down at the contact discontinuity, which appears often in simulations of astronomical objects. At the contact discontinuity, the density of the low-density side is overestimated while that of the high-density side is underestimated. As a result, the pressure of the low (high) density side is over (under) estimated. Thus, unphysical repulsive force appears at the contact discontinuity, resulting in the effective surface tension. This effective surface tension suppresses instabilities such as the Kelvin-Helmholtz and Rayleigh-Taylor instabilities. In this paper, we present a new formulation of SPH, which does not require the differentiability of density and thus can handle contact discontinuity without numerical problems. The results of standard tests such as the shock tube, Kelvin-Helmholtz and Rayleigh-Taylor instabilities, and the blob tests are all very favorable to our new formulation. We conclude that our new formulation solved practically all known difficulties of the standard SPH, without introducing additional numerical diffusion or breaking the exact force symmetry or energy conservation.

At present, 30-40 per cent of the baryons in the local Universe is still undetected. According to theoretical predictions, this gas should reside in filaments filling the large-scale structure (LSS) in the form of a Warm-Hot Intergalactic Medium (WHIM), at temperatures of 10^5 – 10^7 K, thus emitting in the soft X-ray energies via free-free interaction and line emission from heavy elements. In this work we characterize the properties of the X-ray emission of the WHIM, and the LSS in general, focusing on the influence of different physical mechanisms, namely galactic winds (GWs), black-hole feedback and star-formation, and providing estimates of possible observational constraints. To this purpose we use a set of cosmological hydrodynamical simulations that include a self-consistent treatment of star-formation and chemical enrichment of the intergalactic medium, that allows us to follow the evolution of different metal species. We construct a set of simulated light-cones to make predictions of the emission in the 0.3-10 keV energy range. We obtain that GWs increase by a factor of 2 the emission of both galaxy clusters and WHIM. The amount of oxygen at average temperature and, consequently, the amount of expected bright Ovii and Oviii lines is increased by a factor of 3 due to GWs and by 20 per cent when assuming a top-heavy IMF. We compare our results with current observational constraints and find that the emission from faint groups and WHIM should account from half to all of the unresolved X-ray background in the 1-2 keV band.

We estimate the contribution to the extragalactic gamma-ray background (EGRB) from both intrinsic and cascade emissions produced by blazars using a simple semi- analysis method for two models of the blazar gamma-ray luminosity function (GLF). For the cascade emission, we consider two possible contributions: one is due to that the flux of the cascade emission is lower than the Fermi LAT sensitivity (case I), which is independent on the extragalactic magnetic field (EGMF), another is due to the fact that the flux of the cascade emission is larger than the Fermi LAT sensitivity but the emission angle is larger than LAT point-spread-function (PSF) angle (case II), which depends on the EGMF. Our results indicate that (1) blazar contribution to the EGRB is dominant although it depends on the GLF model and the EGMF; (2) the EGMF plays an important role in estimating the contribution from the cascade emission produced by blazars, the contribution from the cascade emission will significantly alter the EGRB spectrum when the strength of the EGMF is large enough (say BEGMF > 10-12 G); and (3) since the cascade emission in case II reaches a saturation when the strength of the EGMF is ? 10-11 G, it is very possible that the contribution from the cascade emission produced by blazars can be considered as another method to probe the upper limit of the strength of the EGMF.

The F-GAMMA program is a coordinated effort to investigate the physics of Active Galactic Nuclei (AGNs) via multi-frequency monitoring of Fermi blazars. In the current study we show and discuss the evolution of broad-band radio spectra, which are measured at ten frequencies between 2.64 and 142 GHz using the Effelsberg 100-m and the IRAM 30-m telescopes. It is shown that any of the 78 sources studied can be classified in terms of their variability characteristics in merely 5 types of variability. It is argued that these can be attributed to only two classes of variability mechanisms. The first four types are dominated by spectral evolution and can be described by a simple two-component system composed of: (a) a steep quiescent spectral component from a large scale jet and (b) a time evolving flare component following the “Shock-in-Jet” evolutionary path. The fifth type is characterised by an achromatic change of the broad band spectrum, which could be attributed to a different mechanism, likely involving differential Doppler boosting caused by geometrical effects. Here we present the classification, the assumed physical scenario and the results of calculations that have been performed for the spectral evolution of flares.

The observed acceleration of the present universe is shown to be well explained by the holographic dark energy characterized by the total comoving horizon of the universe ($\eta$HDE). It is of interest to notice that the very large primordial part of the comoving horizon generated by the inflation of early universe makes the $\eta$HDE behave like a cosmological constant. As a consequence, both the fine-tuning problem and the coincidence problem can reasonably be understood with the inflationary universe and holographical principle. We present a systematic analysis and obtain a consistent cosmological constraint on the $\eta$HDE model based on the recent cosmological observations. It is found that the $\eta$HDE model gives the best-fit result $\Omega_{m0}=0.270$ ($\Omega_{de0}=0.730$) and the minimal $\chi^2_{min}=542.915$ which is compatible with $\chi^2_{\Lambda {\rm CDM}}=542.919$ for the $\Lambda$CDM model.

The observed acceleration of the present universe is shown to be well explained by the holographic dark energy characterized by the total comoving horizon of the universe ($\eta$HDE). It is of interest to notice that the very large primordial part of the comoving horizon generated by the inflation of early universe makes the $\eta$HDE behave like a cosmological constant. As a consequence, both the fine-tuning problem and the coincidence problem can reasonably be understood with the inflationary universe and holographical principle. We present a systematic analysis and obtain a consistent cosmological constraint on the $\eta$HDE model based on the recent cosmological observations. It is found that the $\eta$HDE model gives the best-fit result $\Omega_{m0}=0.270$ ($\Omega_{de0}=0.730$) and the minimal $\chi^2_{min}=542.915$ which is compatible with $\chi^2_{\Lambda {\rm CDM}}=542.919$ for the $\Lambda$CDM model.

We present an analysis of the linear polarization of six active galactic nuclei – 0415+379 (3C~111), 0507+179, 0528+134 (OG+134), 0954+658, 1418+546 (OQ+530), and 1637+574 (OS+562). Our targets were monitored from 2007 to 2011 in the observatory-frame frequency range 80-253 GHz, corresponding to a rest-frame frequency range 88-705 GHz. We find average degrees of polarization m_L ~ 2-7%; this indicates that the polarization signals are effectively averaged out by the emitter geometries. We see indication for fairly strong shocks and/or complex, variable emission region geometries in our sources, with compression factors 10 deg. An analysis of correlations between source fluxes and polarization parameter points out special cases: the presence of (at least) two distinct emission regions with different levels of polarization (for 0415+379) as well as emission from a single, predominant component (for 0507+179 and 1418+546). Regarding the evolution of flux and polarization, we find good agreement between observations and the signal predicted by “oblique shock in jet” scenarios in one source (1418+546). We attempt to derive rotation measures for all sources, leading to actual measurements for two AGN and upper limits for three sources. We derive values of RM = -39,000 +/- 1,000 (stat) +/- 13,000 (sys) rad/m^2 and RM = 420,000 +/- 10,000 (stat) +/- 110,000 (sys) rad/m^2 for 1418+546 and 1637+574, respectively; these are the highest values reported to date for AGN. These values indicate magnetic field strengths of the order ~0.0001 G. For 0415+379, 0507+179, and 0954+658 we derive upper limits |RM| < 17,000 rad/m^2. From the relation |RM| ~ \nu^a we find a = 1.9 +/- 0.3 for 1418+546, in good agreement with a = 2 as expected for a spherical or conical outflow.

In this paper we study the chemical history of low-mass star-forming (SF) galaxies in the local Universe clusters Coma, A1367, A779, and A634. The aim of this work is to search for the imprint of the environment on the chemical evolution of these galaxies. Galaxy chemical evolution is linked to the star formation history (SFH), as well as to the gas interchange with the environment, and low-mass galaxies are well known to be vulnerable systems to environmental processes affecting both these parameters. For our study we have used spectra from the SDSS-III DR8. We have examined the mass-metallicity relation of cluster galaxies finding well defined sequences. The slope of these sequences, for galaxies in low-mass clusters and galaxies at large cluster-centric distances, follows the predictions of recent hydrodynamic models. A flattening of this slope has been observed for galaxies located in the core of the two more massive clusters of the sample, principally in Coma, suggesting that the imprint of the cluster environment on the chemical evolution of SF galaxies should be sensitive to both the galaxy mass and the host cluster mass. The HI gas content of Coma and A1367 galaxies indicate that low-mass SF galaxies, located at the core of these clusters, have been severely affected by ram-pressure stripping. The observed mass-dependent enhancement of the metal content of low-mass galaxies in dense environments seems plausible, according to hydrodynamic simulations. This enhanced metal enrichment could be produced by the combination of effects such as wind reaccretion, due to pressure cofinement by the intra-cluster medium (ICM), and the truncation of gas infall, as a result of the ram-pressure stripping. Thus, the properties of the ICM should play an important role in the chemical evolution of low-mass galaxies in clusters.

Using redshifts as proxy for galaxy distances, estimates of the 2D transverse peculiar velocities of distant galaxies ($cz\ltsim 2\times 10^4 \kms$) can be obtained from Gaia’s measurements of proper motions. Owing to the large number of galaxies expected to be observed by Gaia, these transverse velocities are likely to supersede traditional probes of the large scale velocity field based on current and future distance indicator measurements. This Gaia probe of large scale motions is completely independent of any intrinsic relations between galaxy properties, hence it is essentially free of selection biases. It is also free from {homogeneous and} inhomogeneous Malmquist biases that typically plague distance indicator catalogs. Further, it provides additional information to traditional probes which yield line-of-sight peculiar velocities.

In this paper, we report the results of constraining the dynamical dark energy with a divergence-free parameterization, $w(z) = w_{0} + w_{a}(\frac{\ln(2+z)}{1+z}-\ln2)$, in the presence of spatial curvature and massive neutrinos, with the 7-yr WMAP temperature and polarization data, the power spectrum of LRGs derived from SDSS DR7, the Type Ia supernova data from Union2 sample, and the new measurements of $H_0$ from HST, by using a MCMC global fit method. Our focus is on the determinations of the spatial curvature, $\Omega_k$, and the total mass of neutrinos, $\sum m_{\nu}$, in such a dynamical dark energy scenario, and the influence of these factors to the constraints on the dark energy parameters, $w_0$ and $w_a$. We show that $\Omega_k$ and $\sum m_{\nu}$ can be well constrained in this model; the 95% CL limits are: $-0.0153<\Omega_k<0.0167$ and $\sum m_{\nu}<0.56$ eV. Comparing to the case in a flat universe, we find that the error in $w_0$ is amplified by 25.51%, and the error in $w_a$ is amplified by 0.14%; comparing to the case with a zero neutrino mass, we find that the error in $w_0$ is amplified by 12.24%, and the error in $w_a$ is amplified by 1.63%.

We investigate the Q-ball decay into the axino dark matter in the gauge-mediated supersymmetry breaking. In our scenario, the Q ball decays mainly into nucleons and partially into axinos to account for the baryon asymmetry and the dark matter of the universe simultaneously. The Q ball decays well before the big bang nucleosynthesis so that it is not affected by the decay. The decay into the supersymmetric particles of the minimal supersymmetric standard model is kinematically prohibited until the very end of the decay, and we could safely make their abundances small enough for the successful big bang nucleosynthesis. We show the regions of axino model parameters and the Q-ball parameters which realize this scenario.

We explore the ultimate fate of the Universe by using a divergence-free parametrization for dark energy $w(z)=w_0+w_a({\ln (2+z)\over 1+z}-\ln2)$. Unlike the CPL parametrization, this parametrization has well behaved, bounded behavior for both high redshifts and negative redshifts, and thus can genuinely cover many theoretical dark energy models. After constraining the parameter space of this parametrization by using the current cosmological observations, we find that, at the 95.4% confidence level, our Universe can still exist at least 16.7 Gyr before it ends in a big rip. Moreover, for the phantom energy dominated Universe, we find that a gravitationally bound system will be destroyed at a time $t \simeq P\sqrt{2|1+3w(-1)|}/[6\pi |1+w(-1)|]$, where $P$ is the period of a circular orbit around this system, before the big rip.

Abridged: Four new nuclear star cluster masses, M_nc, plus seven upper limits, are provided for galaxies with previously determined black hole masses, M_bh. Together with a sample of 64 galaxies with direct M_bh measurements, 13 of which additionally now have M_nc measurements rather than only upper limits, plus an additional 29 dwarf galaxies with available M_nc measurements and velocity dispersions sigma, an (M_bh + M_nc)-sigma diagram is constructed. Given that major dry galaxy merger events preserve the M_bh/L ratio, and given that L ~ sigma^5 for luminous galaxies, it is first noted that the observation M_bh ~ sigma^5 is consistent with expectations. For the fainter elliptical galaxies it is known that L ~ sigma^2, and assuming a constant M_nc/L ratio (Ferrarese et al.), the expectation that M_nc ~ sigma^2 is in broad agreement with our new observational result that M_nc ~ sigma^{1.57\pm0.24}. This exponent is however in contrast to the value of ~4 which has been reported previously and interpreted in terms of a regulating feedback mechanism from stellar winds.

We present the smoothness of the mid-infrared sky from observations by the Japanese infrared astronomical satellite AKARI. AKARI monitored the north ecliptic pole (NEP) during its cold phase with nine wavebands covering from 2.4 to 24 \mu m, out of which six mid-infrared bands were used in this study. A simple sinusoidal fit to the seasonal variation of the sky brightness shows that the mid-infrared brightness towards the NEP is not affected by small-scale features of the interplanetary dust cloud. We applied power spectrum analysis to the images in order to search for the fluctuation of the sky brightness. Observed fluctuation is explained by fluctuation of photon noise, shot noise of faint sources, and Galactic cirrus. The fluctuations at a few arcminutes scales at short mid-infrared wavelengths (7, 9, and 11 \mum) are largely caused by the diffuse Galactic light of the interstellar dust cirrus. At long mid-infrared wavelengths (15, 18, and 24 \mum), photon noise is the dominant source of fluctuation over the scale from arcseconds to a few arcminutes. The residual fluctuation power at 200″ after removing these contributions is at most 1.08 \pm 0.22 nW m^-2 sr^-1 or 0.05% of the brightness at 24 \mum and at least 0.52 \pm 0.13 nW m^-2 sr^-1 or 0.02% at 18 \mum. We conclude that the upper limit of the fluctuation in the zodiacal light is 0.02% of the sky brightness.

A leading candidate source of detectable gravitational waves is the inspiral and merger of pairs of stellar-mass compact objects. The advanced LIGO and advanced Virgo detectors will allow scientists to detect inspiral signals from more massive systems and at earlier times in the detector band, than with first generation detectors. The signal from a coalescence of two neutron stars is expected to stay in the sensitive band of advanced detectors for several minutes, thus allowing detection before the final coalescence of the system. In this work, the prospects of detecting inspiral signals prior to coalescence, and the possibility to derive a suitable sky area for source locations are investigated. As a large fraction of the signal is accumulated in the last ~10 seconds prior to coalescence, bandwidth and timing accuracy are largely accrued in the very last moments prior to coalescence. We use Monte Carlo techniques to estimate the accuracy of sky localization through networks of ground-based interferometers such as aLIGO and aVirgo. With the addition of the Japanese KAGRA detector, it is shown that the detection and triangulation before coalescence may be feasible.

A shift of the baryon acoustic oscillation (BAO) scale to smaller values than predicted by linear theory was observed in simulations. In this paper, we try to provide an intuitive physical understanding of why this shift occurs, explaining in more pedagogical detail earlier perturbation theory calculations. We find that the shift is mainly due to the following physical effect. A measurement of the BAO scale is more sensitive to regions with long wavelength overdensities than underdensities, because (due to non-linear growth and bias) these overdense regions contain larger fluctuations and more tracers and hence contribute more to the total correlation function. In overdense regions the BAO scale shrinks because such regions locally behave as positively curved closed universes, and hence a smaller scale than predicted by linear theory is measured in the total correlation function. Other effects which also contribute to the shift are briefly discussed. We provide approximate analytic expressions for the non-linear shift including a brief discussion of biased tracers, and note that the shifts are different in real and Fourier space due to a change of the shape of the BAO feature. We explain why reconstruction should entirely reverse the shift. Our expressions and findings are in agreement with simulation results, and confirm that non-linear shifts should not be problematic for next-generation BAO measurements.

Changes in the values of the fundamental constants mu, the proton to electron mass ratio, and alpha, the fine structure constant due to rolling scalar fields have been discussed both in the context of cosmology and in new physics such as Super Symmetry (SUSY) models. This article examines the changes in these fundamental constants in a particular example of such fields, freezing and thawing slow roll quintessence. Constraints are placed on the product of a cosmological quantity, w, the equation of state parameter, and the square of the coupling constants for mu and alpha with the field, zeta_x, x = mu,alpha, using the existing observational limits on the values of Delta x/x. Various examples of slow rolling quintessence models are used to further quantify the constraints. Some of the examples appear to be rejected by the existing data which strongly suggests that conformation to the values of the fundamental constants in the early universe is a standard test that should be applied to any cosmological model or suggested new physics.

We identify near-infrared Ks band counterparts to Herschel-ATLAS sub-mm sources, using a preliminary object catalogue from the VISTA VIKING survey. The sub-mm sources are selected from the H-ATLAS Phase 1 catalogue of the GAMA 9h field, which includes all objects detected at 250, 350 or 500 um with the SPIRE instrument. We apply and discuss a likelihood ratio (LR) method for VIKING candidates within a search radius of 10″ of the 22,000 SPIRE sources with a 5 sigma detection at 250 um. We find that 11,294(51%) of the SPIRE sources have a best VIKING counterpart with a reliability $R\ge 0.8$, and the false identification rate of these is estimated to be 4.2%. We expect to miss ~5% of true VIKING counterparts. There is evidence from Z-J and J-Ks colours that the reliable counterparts to SPIRE galaxies are marginally redder than the field population. We obtain photometric redshifts for ~68% of all (non-stellar) VIKING candidates with a median redshift of 0.405. Comparing to the results of the optical identifications supplied with the Phase I catalogue, we find that the use of medium-deep near-infrared data improves the identification rate of reliable counterparts from 36% to 51%.

In this paper, a periodicity analysis of the radio light curves of the blazar NRAO 530 at 14.5, 8.0, and 4.8 GHz is presented employing an improved Phase Dispersion Minimization (PDM) technique. The result, which shows two persistent periodic components of $ \sim 6$ and $ \sim 10$ years at all three frequencies, is consistent with the results obtained with the Lomb-Scargle periodogram and weighted wavelet Z-transform algorithms. The reliability of the derived periodicities is confirmed by the Monte Carlo numerical simulations which show a high statistical confidence. (Quasi-)Periodic fluctuations of the radio luminosity of NRAO 530 might be associated with the oscillations of the accretion disk triggered by hydrodynamic instabilities of the accreted flow. \keywords{methods: statistical — galaxies: active — galaxies: quasar: individual: NRAO 530}

We study the relative alignment of mass and light in a sample of 16 massive early-type galaxies at z=0.2-0.9 that act as strong gravitational lenses. The sample was identified from deep multiband images obtained as part of the Canada France Hawaii Legacy Survey (CFHTLS) as part of the Strong Lensing Legacy Survey (SL2S). Higher resolution follow-up imaging is available for a subset of 10 systems. We construct gravitational lens models and infer total enclosed mass, elongation, and position angle of the mass distribution. By comparison with the observed distribution of light we infer that there is a substantial amount of external shear $ \approx 0.12$, arising most likely from the environment of the SL2S lenses. In a companion paper (Ruff et al. 2011) we combine these measurements with follow-up Keck spectroscopy to study the evolution of the stellar and dark matter content of early-type galaxies as a function of cosmic time.

Supermassive black holes exist in the centers of galaxies, including Milky Way, but there is no compelling theory of their formation. Furthermore, observations of quasars imply that supermassive black holes have already existed at some very high redshifts, suggesting the possibility of their primordial origin. In a class of well-motivated models, inflationary epoch could include two or more periods of inflation dominated by different scalar fields. The transition between such periods of inflation could enhance the spectrum of density perturbations on some specific scale, which could lead to formation of primordial black holes with a very narrow range of masses of the order of 0.1 to 1 million solar masses. These primordial black holes could have provided the requisite seeds for the observed population of supermassive black holes.

The construction of the Cosmicflows-2 compendium of distances involves the merging of distance measures contributed by the following methods: (Cepheid) Period-Luminosity, Tip of the Red Giant Branch (TRGB), Surface Brightness Fluctuation (SBF), Luminosity-Linewidth (TF), Fundamental Plane (FP), and Type Ia supernova (SNIa). The method involving SNIa is at the top of an interconnected ladder, providing accurate distances to well beyond the expected range of distortions to Hubble flow from peculiar motions. In this paper, the SNIa scale is anchored by 36 TF spirals with Cepheid or TRGB distances, 56 SNIa hosts with TF distances, and 61 groups or clusters hosting SNIa with Cepheid, SBF, TF, or FP distances. With the SNIa scale zero point set, a value of the Hubble Constant is evaluated over a range of redshifts 0.03 < z < 0.5, assuming a cosmological model with Omega_m = 0.27 and Omega_Lambda = 0.73. The value determined for the Hubble Constant is H0 = 75.9 \pm 3.8 km s-1 Mpc-1.

Contamination from instrumental effects interacting with bright astrophysical sources is the primary impediment to measuring Epoch of Reionization and BAO 21 cm power spectra-an effect called mode-mixing. In this paper we identify four fundamental power spectrum shapes produced by mode-mixing that will affect all upcoming observations. We are able, for the first time, to explain the wedge-like structure seen in advanced simulations and to forecast the shape of an ‘EoR window’ that is mostly free of contamination. Understanding the origins of these contaminations also enables us to identify calibration and foreground subtraction errors below the imaging limit, providing a powerful new tool for precision observations.

We present tentative evidence for the existence of a dissolved star cluster in the Sextans dwarf spheroidal galaxy. In a sample of six stars, we identify three (possibly four) stars around [Fe/H] =-2.7 that are highly clustered in a multi-dimensional chemical abundance space. The estimated initial stellar mass of the cluster is M*,init = 1.9^+1.5_-0.9 (1.6^+1.2_-0.8)*10^5 Msol assuming a Salpeter (Kroupa) initial mass function (IMF). If corroborated by follow-up spectroscopy, this ancient star cluster at [Fe/H] =-2.7 is the most metal-poor system identified to date. Inspired by this finding, we also present a new way to interpret the cumulative metallicity functions of dwarf galaxies. From available observational data, we speculate that the ultra-faint dwarf galaxy population, or a significant fraction thereof, and the more luminous, classical dwarf spheroidal population were formed in different environments and would thus be distinct in origin.

We study a sample of 39 massive early-type lens galaxies at redshift z < 0.3 to determine the slope of the average dark-matter density profile in the innermost regions. We keep the strong lensing and stellar population synthesis modeling as simple as possible to measure the galaxy total and luminous masses. By rescaling the values of the Einstein radius and dark-matter projected mass with the values of the luminous effective radius and mass, we combine all the data of the galaxies in the sample. We find that between 0.3 and 0.9 times the value of the effective radius the average logarithmic slope of the dark-matter projected density profile is -1.0 +/- 0.2 (i.e., approximately isothermal) or -0.7 +/- 0.5 (i.e., shallower than isothermal), if, respectively, a constant Chabrier or heavier, Salpeter-like stellar IMF is adopted. These results provide positive evidence of the influence of the baryonic component on the contraction of the galaxy dark-matter halos, compared to the predictions of dark matter-only cosmological simulations, and open a new way to test models of structure formation and evolution within the standard LCDM cosmological scenario.

B2 0954+25A, detected by the {\it Fermi} satellite, is a blazar with interesting observational properties: it has been observed to transit from a jet dominated to a disk dominated state; its radio spectrum appears flat at all observing frequencies (down to 74 MHz); optically, the H$\beta$ line profile is asymmetric. The flatness of radio spectrum suggests that the isotropic emission from radio lobes is very weak, despite the large size of its jet ($\gtrsim$ 500 kpc). Its broad–band spectral energy distribution is surprisingly similar to that of the prototypical $\gamma$–ray, radio loud, Narrow Line Seyfert 1 ($\gamma$–NLS1) galaxy PMN J0948+0022. In this work we revisit the mass estimates of B2 0954+25A considering only the symmetric component of the H$\beta$ line and find (1–3) $\times 10^8$ M$_{\sun}$. In light of our composite analysis, we propose to classify the source as a transition object between the class of Flat Spectrum Radio Quasar and $\gamma$–ray, radio loud NLS1. A comparison with two members of each class (3C 273 and PMN J0948+0022) is discussed.

While O is often seen in spectra of Type Ia supernovae (SNe Ia) as both unburned fuel and a product of C burning, C is only occasionally seen at the earliest times, and it represents the most direct way of investigating primordial white dwarf material and its relation to SN Ia explosion scenarios and mechanisms. In this paper, we search for C absorption features in 188 optical spectra of 144 low-redshift (z < 0.1) SNe Ia with ages <3.6 d after maximum brightness. These data were obtained as part of the Berkeley SN Ia Program (BSNIP; Silverman et al. 2012a,b, submitted) and represent the largest spectral dataset in which C has ever been searched. We find that ~11 per cent of the SNe studied show definite C absorption features while ~25 per cent show some evidence for C II in their spectra. Also, if one obtains a spectrum at t < -5 d, then there is a better than 30 per cent chance of detecting a distinct absorption feature from C II. SNe Ia that show C are found to resemble those without C in many respects, but objects with C tend to have bluer optical colours than those without. The typical expansion velocity of the C II 6580 Ang. feature is measured to be 12,000-13,000 km/s, and the ratio of the C II 6580 Ang. to Si II 6355 Ang. velocities is remarkably constant with time and among different objects with a median value of ~1.05. While the pseudo-equivalent widths (pEWs) of the C II 6580 Ang. and C II 7234 Ang. features are found mostly to decrease with time, we see evidence of a significant increase in pEW between ~12 and 11 d before maximum brightness, which is actually predicted by some theoretical models. The range of pEWs measured from the BSNIP data implies a range of C mass in SN Ia ejecta of about (2-30) x 10^{-3} M_Sun.

Using a sample of 123 X-ray clusters and groups drawn from the XMM-Cluster Survey first data release, we investigate the interplay between the brightest cluster galaxy (BCG), its black hole, and the intra-cluster/group medium (ICM). It appears that for groups and clusters with a BCG likely to host significant AGN feedback, gas cooling dominates in those with Tx > 2 keV while AGN feedback dominates below. This may be understood through the sub-unity exponent found in the scaling relation we derive between the BCG mass and cluster mass over the halo mass range 10^13 < M500 2 keV) and again co-located with an effective fuel supply of dense, cooling gas. This demonstrates that the most massive black holes appear to know more about their host cluster than they do about their host galaxy. The results lead us to propose a physically motivated, empirical definition of ‘cluster’ and ‘group’, delineated at 2 keV.

We discuss some practical aspects of measuring the variability amplitude of faint and distant active galactic nuclei (AGN), characterized by sparsely sampled lightcurves and low statistic. In such cases the excess variance, commonly used to estimate the intrinsic lightcurve variance, is affected by strong biases and uncertainties since it represents a maximum likelihood variability estimator only for identical/normal distributed measurements errors and uniform sampling. We performed realistic Monte Carlo simulations of AGN lightcurves, reproducing both the sampling pattern and measurement errors typical of multi-epoch deep surveys, such as the XMM-Newton observations of the Chandra Deep Field South (CDFS), or assuming different sampling patterns that may characterize long surveys with sub-optimal observing conditions. We used the results to estimate our ability to measure the intrinsic source variability as well as to constrain the observing strategy of future X-ray missions studying distant and/or faint AGN populations.

We discuss some practical aspects of measuring the variability amplitude of faint and distant active galactic nuclei (AGN), characterized by sparsely sampled lightcurves and low statistic. In such cases the excess variance, commonly used to estimate the intrinsic lightcurve variance, is affected by strong biases and uncertainties since it represents a maximum likelihood variability estimator only for identical/normal distributed measurements errors and uniform sampling. We performed realistic Monte Carlo simulations of AGN lightcurves, reproducing both the sampling pattern and measurement errors typical of multi-epoch deep surveys, such as the XMM-Newton observations of the Chandra Deep Field South (CDFS), or assuming different sampling patterns that may characterize long surveys with sub-optimal observing conditions. We used the results to estimate our ability to measure the intrinsic source variability as well as to constrain the observing strategy of future X-ray missions studying distant and/or faint AGN populations.

The damped random walk (DRW) model is increasingly used to model the variability in quasar light curves, but it is still uncertain whether the DRW model provides an adequate description of quasar variability across all time scales. Using a sample of OGLE quasar light curves, we consider four modifications to the DRW model by introducing additional parameters into the covariance function to search for deviations from the DRW model on both short and long time scales. We find excellent agreement with the DRW model on time scales that are well sampled by the data (from a month to a few years), possibly with some intrinsic scatter in the additional parameters. On very short time scales (below a few months), we see some evidence of the existence of a cutoff time scale below which the correlation is stronger than the DRW model, echoing the recent finding of Mushotzky et al. (2011) using quasar light curves from Kepler. On very long time scales (> a few years), the light curves do not constrain models well, but are generally consistent with the DRW model.

In the N=1 four-dimensional new-minimal supergravity framework, we supersymmetrise the coupling of the scalar kinetic term to the Einstein tensor. This coupling, although introduces a non-minimal derivative interaction of curvature to matter, it does not introduce harmful higher-derivatives. For this construction, we employ off-shell chiral and real linear multiplets. Physical scalars are accommodated in the chiral multiplet whereas curvature resides in a linear one.

We propose that the early Universe was not Lorentz symmetric and that a gradual transition to the Lorentz symmetric phase occurred. An underlying form of the Dirac equation hints to such a transition for fermions. Fermions were coupled to space-time in a non-trivial manner such that they were massless in the Lorentz violating phase. The partition function is used as a transfer matrix to model this transition on a two level thermodynamics system that describes how such a transition might have occurred. The system that models this transition evolves, with temperature, from a state of large to negligible entropy and this is interpreted as describing the transition to a state with Lorentz symmetry. In addition to this, analogy is created with the properties of this system to describe how the fields were massless and how a baryon asymmetry can be generated in this model.