We investigate the accuracy of Eulerian perturbation theory for describing the matter and galaxy power spectra in real and redshift space in light of future observational probes for precision cosmology. Comparing the analytical results with a large suite of N-body simulations (160 independent boxes of 13.8 (Gpc/h)^3 volume each, which are public available), we find that re-summing terms in the standard perturbative approach predicts the real-space matter power spectrum with an accuracy of <2% for k<0.20 h/Mpc at redshifts z<1.5. This is obtained following the widespread technique of writing the resummed propagator in terms of 1-loop contributions. We show that the accuracy of this scheme increases by considering higher-order terms in the resummed propagator. By combining resummed perturbation theories with several models for the mappings from real to redshift space discussed in the literature, the multipoles of the dark-matter power spectrum can be described with sub-percent deviations from N-body results for k<0.15h/Mpc at z<1. As a consequence, the logarithmic growth rate, f, can be recovered with sub-percent accuracy on these scales. Extending the models to dark-matter haloes in redshift space, our results describe the monopole term from N-body data within 2% accuracy for scales k<0.15h/Mpc at z<0.5; here f can be recovered within <5% when the halo bias is known. We conclude that these techniques are suitable to extract cosmological information from future galaxy surveys.
Determining the virial factor of the broad-line region (BLR) gas is crucial for calibrating AGN black hole mass estimators, since the measured line-of-sight velocity needs to be converted into the intrinsic virial velocity. The average virial factor has been empirically calibrated based on the M-sigma relation of quiescent galaxies, but the claimed values differ by a factor of two in recent studies. We investigate the origin of the difference by measuring the M-sigma relation using an updated galaxy sample from the literature, and explore the dependence of the virial factor on various fitting methods. We find that the discrepancy is primarily caused by the sample selection, while the difference stemming from the various regression methods is marginal. However, we generally prefer the FITEXY and Bayesian estimators based on Monte Carlo simulations for the M-sigma relation. In addition, the choice of independent variable in the regression leads to ~0.2 dex variation in the virial factor inferred from the calibration process. Based on the determined virial factor, we present the updated M-sigma relation of local active galaxies.
The infall regions of galaxy clusters represent the largest gravitationally bound structures in a $\Lambda$CDM universe. Measuring cluster mass profiles into the infall regions provides an estimate of the ultimate mass of these haloes. We use the caustic technique to measure cluster mass profiles from galaxy redshifts obtained with the Hectospec Cluster Survey (HeCS), an extensive spectroscopic survey of galaxy clusters with MMT/Hectospec. We survey 58 clusters selected by X-ray flux at 0.1$<$$z$$<$0.3. The survey includes 21,314 unique MMT/Hectospec redshifts for individual galaxies; 10,275 of these galaxies are cluster members. For each cluster we acquired high signal-to-noise spectra for $\sim 200$ cluster members and a comparable number of foreground/background galaxies. The cluster members trace out infall patterns around the clusters. The members define a very narrow red sequence. The velocity dispersions decline with radius; we demonstrate that the determination of the velocity dispersion is insensitive to the inclusion of bluer members (a small fraction of the cluster population). We apply the caustic technique to define membership and estimate the mass profiles to large radii. The ultimate halo mass of clusters (the mass that remains bound in the far future of a $\Lambda$CDM universe) is on average (1.99$\pm$0.11)$M_{200}$, a new observational cosmological test in essential agreement with simulations. Summed profiles binned in $M_{200}$ and in $L_X$ demonstrate that the predicted NFW form of the density profile is a remarkably good representation of the data in agreement with weak lensing results extending to large radius. The concentration of these summed profiles is also consistent with theoretical predictions.
We propose a co-ordinated multi-observatory survey at the North Ecliptic Pole. This field is the natural extragalactic deep field location for most space observatories (e.g. containing the deepest Planck, WISE and eROSITA data), is in the continuous viewing zones for e.g. Herschel, HST, JWST, and is a natural high-visibility field for the L2 halo orbit of SPICA with deep and wide-field legacy surveys already planned. The field is also a likely deep survey location for the forthcoming Euclid mission. It is already a multi-wavelength legacy field in its own right (e.g. AKARI, LOFAR, SCUBA-2): the outstanding and unparalleled continuous mid-IR photometric coverage in this field and nowhere else enables a wide range of galaxy evolution diagnostics unachievable in any other survey field, by spanning the wavelengths of redshifted PAH and silicate features and the peak energy output of AGN hot dust. We argue from the science needs of Euclid and JWST, and from the comparative multiwavelength depths, that the logical approach is (1) a deep (H-UDF) UV/optical tile in the NEP over ~10 square arcminutes, and (2) an overlapping wide-field UV/optical HST survey tier covering >100 square arcminutes, with co-ordinated submm SPIRE mapping up to or beyond the submm point source confusion limit over a wider area and PACS data over the shallower HST tier.
We present the spatially resolved emission line ratio properties of a ~10^10 M_sun star-forming galaxy at redshift z=1.03. This galaxy is gravitationally lensed as a triple-image giant arc behind the massive lensing cluster Abell 2667. The main image of the galaxy has magnification factors of 14+/-2.1 in flux and ~ 2 by 7 in area, yielding an intrinsic spatial resolution of 115-405 pc after AO correction with OSIRIS at KECK II. The HST morphology shows a clumpy structure and the H\alpha\ kinematics indicates a large velocity dispersion with V_{max} sin(i)/\sigma ~ 0.73, consistent with high redshift disk galaxies of similar masses. From the [NII]/H\alpha\ line ratios, we find that the central 350 parsec of the galaxy is dominated by star formation. The [NII]/H\alpha\ line ratios are higher in the outer-disk than in the central regions. Most noticeably, we find a blue-shifted region of strong [NII]/H\alpha\ emission in the outer disk. Applying our recent HII region and slow-shock models, we propose that this elevated [NII]/H\alpha\ ratio region is contaminated by a significant fraction of shock excitation due to galactic outflows. Our analysis suggests that shocked regions may mimic flat or inverted metallicity gradients at high redshift.
We present systematic case studies to investigate the sensitivity of axion searches by liquid xenon detectors, using the axio-electric effect (analogue of the photoelectric effect) on xenon atoms. Liquid xenon is widely considered to be one of the best target media for detection of WIMPs (Weakly Interacting Massive Particles which may form the galactic dark matter) using nuclear recoils. Since these detectors also provide an extremely low radioactivity environment for electron recoils, very weakly-interacting low-mass particles (< 100 keV/c^2), such as the hypothetical axion, could be detected as well - in this case using the axio-electric effect. Future ton-scale liquid Xe detectors will be limited in sensitivity only by irreducible neutrino background (pp-chain solar neutrino and the double beta decay of 136Xe) in the mass range between 1 and 100 keV/c^2. Assuming one ton-year of exposure, galactic axions (as non-relativistic dark matter) could be detected if the axio-electric coupling g_Ae is greater than 10^-14 at 1 keV/c^2 (or $10^-13 at 100 keV/c^2). Below a few keV/c^2, and independent of the mass, a solar axion search would be sensitive to a coupling g_Ae ~ 10^-12. This limit will set a stringent upper bound on axion mass for the DFSV and KSVZ models for the mass ranges m_A < 0.1 eV/c^2 and < 10 eV/c^2, respectively. Vector-boson dark matter could also be detected for a coupling constant alpha'/alpha > 10^-33 (for mass 1 keV/c^2) or > 10^-27 (for mass 100 keV/c^2).
The stochastic gravitational-wave background (SGWB) is expected to arise from the superposition of many independent and unresolved gravitational-wave signals of either cosmological or astrophysical origin. The spectral content of the SGWB carries signatures of the physics that generated it. We present a Bayesian framework for estimating the parameters associated with different SGWB models using data from gravitational-wave detectors. We apply this technique to recent results from LIGO to produce the first simultaneous 95% confidence level limits on multiple parameters in generic power-law SGWB models and in SGWB models of compact binary coalescences. We also estimate the sensitivity of the upcoming second-generation detectors such as Advanced LIGO/Virgo to these models and demonstrate how SGWB measurements can be combined and compared with observations of individual compact binary coalescences in order to build confidence in the origin of an observed SGWB signal. In doing so, we demonstrate a novel means of differentiating between different sources of the SGWB.
Recent success in explaining several properties of the dusty torus around the central engine of active galactic nuclei has been gathered with the assumption of clumpiness. The properties of such clumpy dusty tori can be inferred by analyzing spectral energy distributions (SEDs), sometimes with scarce sampling given that large aperture telescopes and long integration times are needed to get good spatial resolution and signal. We aim at using the information already present in the data and the assumption of clumpy dusty torus, in particular, the CLUMPY models of Nenkova et al., to evaluate the optimum next observation such that we maximize the constraining power of the new observed photometric point. To this end, we use the existing and barely applied idea of Bayesian adaptive exploration, a mixture of Bayesian inference, prediction and decision theories. The result is that the new photometric filter to use is the one that maximizes the expected utility, which we approximate with the entropy of the predictive distribution. In other words, we have to sample where there is larger variability in the SEDs compatible with the data with what we know of the model parameters. We show that Bayesian adaptive exploration can be used to suggest new observations, and ultimately optimal filter sets, to better constrain the parameters of the clumpy dusty torus models. In general, we find that the region between 10 and 200 um produces the largest increase in the expected utility, although sub-mm data from ALMA also prove to be useful. It is important to note that here we are not considering the angular resolution of the data, which is key when constraining torus parameters. Therefore, the expected utilities derived from this methodology must be weighted with the spatial resolution of the data.
We use the most up-to-date cosmological evolution models of star-forming (SF) galaxies and radio sources to compute the extragalactic number counts and the cosmic background from 408MHz to 12THz. The model of SF galaxies reproduces the constraints obtained by Spitzer, Herschel, and ground-based submm/mm experiments: number counts, redshift distribution of galaxies, cosmic background intensity and anisotropies. The template SEDs of this model are extrapolated to the radio adding synchrotron, free-free, and spinning dust emissions. To fix the synchrotron intensity, we use the IR/radio flux ratio, q70, and a spectral index beta=-3. For a constant q70, our model added to the AGN contribution provides a good fit to the number counts from 12THz to 408MHz and to the CIB. Spinning dust accounts for up to 20% of the cosmic microwave background produced by SF galaxies, but for less than 10% of the total background when AGN are included. The SF galaxies account for 77.5% of the number counts at 1.4GHz for a flux of 1e-4Jy. However, the model does not explain the CRB measured with the ARCADE2 experiment. Considering the case when q70 decreases strongly with redshift, this still does not explain the ARCADE2 results. It also yields to an overestimate of the low-flux number counts in the radio. Thus, we rule out a steep variation of q70 with redshift at least for z<3.5. Adding a population of faint SF galaxies at high redshift (Lir<1e11Lsun and 4<z<6), which would reproduce the ARCADE2 results, leads to predictions of the CIB much higher than what is observed, ruling out this as the explanation for the ARCADE2 results. Considering our findings and previous studies, we conclude that if the radio emission measured by ARCADE2 is astrophysical in origin, it has to originate in the Galaxy or in a new kind of radio sources (with no mid- to far-IR counterparts) or emission mechanism still to be discovered.
We present a spectroscopic analysis of the metallicities, ages, and alpha-elements of the globular clusters (GCs) in the giant elliptical galaxy (gE) NGC 4636 in the Virgo cluster. Line indices of the GCs are measured from the integrated spectra obtained with Faint Object Camera and Spectrograph (FOCAS) on the Subaru 8.2 m telescope. We derive [Fe/H] values of 59 GCs based on the Brodie & Huchra method, and [Z/H], age, and [a/Fe] values of 33 GCs from the comparison of the Lick line indices with single stellar population models. The metallicity distribution of NGC 4636 GCs shows a hint of a bimodality with two peaks at [Fe/H]=-1.23 (sigma=0.32) and -0.35 (sigma=0.19). The age spread is large from 2 Gyr to 15 Gyr and the fraction of young GCs with age < 5 Gyr is about 27%. The [a/Fe] of the GCs shows a broad distribution with a mean value [a/Fe]~0.14 dex. The dependence of these chemical properties on the galactocentric radius is weak. We also derive the metallicities, ages, and [a/Fe] values for the GCs in other nearby gEs (M87, M49, M60, NGC 5128, NGC 1399, and NGC 1407) from the line index data in the literature using the same methods as used for NGC 4636 GCs. The metallicity distribution of GCs in the combined sample of seven gEs including NGC 4636 is found to be bimodal, supported by the KMM test with a significance level of >99.9%. All these gEs harbor some young GCs with ages less than 5 Gyr. The mean age of the metal-rich GCs ([Fe/H] > -0.9) is about 3 Gyr younger than that of the metal-poor GCs. The mean value of [a/Fe] of the gE GCs is smaller than that of the Milky Way GCs. We discuss these results in the context of GC formation in gEs.
We present a measurement of the quasar luminosity function in the range 0.68<z<4 down to extinction corrected magnitude g_dered=22.5, using a simple and well understood target selection technique based on the time-variability of quasars. The completeness of our sample was derived directly from a control sample of quasars, without requiring complex simulations of quasar light-curves or colors. A total of 1877 quasar spectra were obtained from dedicated programs on the Sloan telescope (as part of the SDSS-III/BOSS survey) and on the Multiple Mirror Telescope. They allowed us to derive the quasar luminosity function. It agrees well with previously published results from Croom et al. (2009) in the common redshift range 0.68<z<2.6. Our deeper data also allow us to extend the measurement to z=4. We measured quasar densities to g_dered<22.5, obtaining 30 QSO per deg^2 at z<1, 99 QSO per deg^2 for 1<z<2.15, and 47 QSO per deg^2 at z>2.15. Using pure luminosity evolution models, we fitted our LF measurements combined with the data from Croom et al. (2009), and predicted quasar number counts as a function of redshift and observed magnitude. These predictions are useful inputs for future cosmology surveys such as those relying on the observation of quasars to measure baryon acoustic oscillations.
In this paper, we introduce the local Minkowski Functions and apply them as the statistics to study the local properties of WMAP Cold Spot (CS) at different scales. We find that these local statistics always excess at the scale of $R\sim 5^{\circ}$ comparing with other spots of WMAP data, which clearly presents the non-Gaussianity of CS and its characteristic scale. Meanwhile, we find that the cosmic texture can excellently explain all the excesses in these statistics, which supports the cosmic texture explanation of WMAP CS.
We review cosmological backgrounds of gravitational waves with a particular attention to the scientific potential of the eLISA/NGO mission. After an overview of cosmological backgrounds and detectors, we consider different cosmological sources that could lead to an observable signal. We then study the backgrounds produced by first-order phase transitions and networks of cosmic strings, assessing the prospects for their detection.
By integration of generalized BSBM and Brans-Dicke cosmological models, in this article, we investigate the theoretical framework of fine structure constant variation and current cosmic acceleration. We first develop a mathematical formalism to analyze the stability of the model. By employing observational data to constrain the model parameters, phase space description is performed and the attractor solutions of the model are detected. We then examine the model against observational data such as Hubble parameter dataset and quasar absorption spectra. The results confirms current universe acceleration and also predicts fine structure constant variation. Furthermore, extrapolation of the best fitted model in high redshift ($z> 15$) shows a significantly larger variation of fine structure constant in earlier epoch of the universe.
We investigate the use of optical photometric variability to select and identify blazars in large-scale time-domain surveys, in part to aid in the identification of blazar counterparts to the ~30% of gamma-ray sources in the Fermi 2FGL catalog still lacking reliable associations. Using data from the optical LINEAR asteroid survey, we characterize the optical variability of blazars by fitting a damped random walk model to individual light curves with two main model parameters, the characteristic timescales of variability (tau), and driving amplitudes on short timescales (sigma). Imposing cuts on minimum tau and sigma allows for blazar selection with high efficiency E and completeness C. To test the efficacy of this approach, we apply this method to optically variable LINEAR objects that fall within the several-arcminute error ellipses of gamma-ray sources in the Fermi 2FGL catalog. Despite the extreme stellar contamination at the shallow depth of the LINEAR survey, we are able to recover previously-associated optical counterparts to Fermi AGN with E > 88% and C = 88% in Fermi 95% confidence error ellipses having semimajor axis r < 8'. We find that the suggested radio counterpart to Fermi source 2FGL J1649.6+5238 has optical variability consistent with other gamma-ray blazars, and is likely to be the gamma-ray source. Our results suggest that the variability of the non-thermal jet emission in blazars is stochastic in nature, with unique variability properties due to the effects of relativistic beaming. After correcting for beaming, we estimate that the characteristic timescale of blazar variability is ~3 years in the rest-frame of the jet, in contrast with the ~320 day disk flux timescale observed in quasars. The variability-based selection method presented will be useful for blazar identification in time-domain optical surveys, and is also a probe of jet physics.
We present velocity dispersion measurements of 20 Local Group stellar clusters (7 < log(age [yrs]) < 10.2) from integrated light spectra and examine the evolution of the stellar mass-to-light ratio, Upsilon_*. We find that the clusters deviate from the evolutionary tracks corresponding to simple stellar populations drawn from standard stellar initial mass functions (IMFs). The nature of this failure, in which Upsilon_* is at first underestimated and then overestimated with age, invalidates potential simple solutions involving a rescaling of either the measured masses or modeled luminosities. A range of possible shortcomings in the straightforward interpretation of the data, including subtleties arising from cluster dynamical evolution on the present day stellar mass functions and from stellar binarity on the measured velocity dispersions, do not materially affect this conclusion given the current understanding of those effects. Independent of further conjectures regarding the origin of this problem, this result highlights a basic failing of our understanding of the integrated stellar populations of these systems. We propose the existence of two distinct initial mass functions, one primarily, but not exclusively, valid for older, metal poor clusters and the other for primarily, but not exclusively, younger, metal rich clusters. The young (log(age [yrs])< 9.5) clusters are well-described by a bottom-heavy IMF, such as a Salpeter IMF, while the older clusters are better described by a top-heavy IMF, such as a light-weighted Kroupa IMF, although neither of these specific forms is a unique solution. The sample is small, with the findings currently depending on the results for four key clusters, but doubling the sample is within reach.
The energy of a test particle orbiting a Schwarzschild black hole is quantized owing to the quantization of the angular momentum. For smallest stable circular orbit, the excitation energy is found to resemble closely the expression for the temperature of the Hawking radiation. This result is consistent with the Unruh effect for orbiting test particle. The predicted energy quantization might be observable by studies of the red-shifted 21-cm line of neutral hydrogen orbiting a primordial black hole with mass of the order of that of Earth.
We consider the effects of fields with suddenly changing mass on the inflationary power spectra. In this context, when a field becomes light, it will be excited. This process contributes to the tensor power spectrum. We compute these effects in a gauge-invariant manner, where we use a novel analytical method for evaluating the corrections to the tensor spectrum due to these excitations. In the case of a scalar field, we show that the net impact on the tensors is small as long as the perturbative expansion is valid. Thus, in these scenarios, measurement of tensor modes is still in one-to-one correspondence with the Hubble scale.
Unbound interacting compact binaries emit gravitational radiation in a wide frequency range. Since short burst-like signals are expected in future detectors, such as LISA or advanced LIGO, it is interesting to study their energy spectrum and the position of the frequency peak. Here we derive them for a system of massive objects interacting on hyperbolic orbits within the quadrupole approximation, following the work of Capozziello et al. In particular, we focus on the derivation of an analytic formula for the energy spectrum of the emitted waves. Within numerical approximation our formula is in agreement with the two known limiting cases: for the eccentricity {\epsilon} = 1, the parabolic case, whose spectrum was computed by Berry and Gair, and the large {\epsilon} limit with the formula given by Turner.
Primary graviton spectra, produced via stimulated emission from an initial Bose-Einstein distribution, are enhanced for typical scales larger than the redshifted thermal wavelength. A mixed state of phonons induces a secondary graviton spectrum which is hereunder computed in terms of three parameters (i.e. the number of phonon species, the tensor-to-scalar ratio and the thermal wavelengths of the mixture). The primary and secondary graviton spectra are shown to be sensitive, respectively, to the first-order and second-order correlation properties of the initial quantum mixture so that the semiclassical theory is argued to be generally inadequate in this context. For particular values of the parameters the secondary contribution may turn out to be comparable with the primary spectrum over large-scales.
Using information from a recent dark matter symposium at Marina del Rey, we discuss the most recent evidence and constraints on low mass WIMPs. There are now five separate experimental limits on such WIMPs, including a new paper on the XENON100 225 day exposure. There are very different experimental methods with different backgrounds that comprise this limit. We speculate on the possible sources of the reported low mass WIMP signals and background.
X-ray bright active galactic nuclei represent a unique astrophysical laboratory for studying accretion physics around super-massive black holes. 4U 1344-60 is a bright Seyfert galaxy which revealed relativistic reflection features in the archival XMM-Newton observation. We present the spectroscopic results of new data obtained with the Suzaku satellite and compare them with the previous XMM-Newton observation. The X-ray continuum of 4U 1344-60 can be well described by a power-law component with the photon index ~ 1.7 modified by a fully and a partially covering local absorbers. We measured a substantial decrease of the fraction of the partially absorbed radiation from around 45% in the XMM-Newton observation to less than 10% in the Suzaku observation while the power-law slope remains constant within uncertainties. The iron line in the Suzaku spectrum is relatively narrow, $\sigma=(0.08 \pm 0.02)$ keV, without any suggestion for relativistic broadening. Regarding this, we interpret the iron line in the archival XMM-Newton spectrum as a narrow line of the same width plus an additional red-shifted emission around 6.1 keV. No evidence of the relativistic reflection is present in the Suzaku spectra. The detected red-shifted iron line during the XMM-Newton observation could be a temporary feature either due to locally enhanced emission or decreased ionisation in the innermost accretion flow.
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We present a spectro-photometric survey of 2522 extragalactic globular clusters (GCs) around twelve early-type galaxies, nine of which have not been published previously. Combining space-based and multi-colour wide field ground-based imaging, with spectra from the Keck DEIMOS instrument, we obtain an average of 160 GC radial velocities per galaxy, with a high velocity precision of 15 km/s per GC. After studying the photometric properties of the GC systems, such as their spatial and colour distributions, we focus on the kinematics of metal-poor (blue) and metal-rich (red) GC subpopulations to an average distance of ~8 effective radii from the galaxy centre. Our results show that for some systems the bimodality in GC colour is also present in GC kinematics. The kinematics of the red GC subpopulations are strongly coupled with the host galaxy stellar kinematics. The blue GC subpopulations are more dominated by random motions, especially in the outer regions, and decoupled from the red GCs. Peculiar GC kinematic profiles are seen in some galaxies: the blue GCs in NGC 821 rotate along the galaxy minor axis, whereas the GC system of the lenticular galaxy NGC 7457 appears to be strongly rotation supported in the outer region. We supplement our galaxy sample with data from the literature and carry out a number of tests to study the kinematic differences between the two GC subpopulations. We confirm that the GC kinematics are coupled with the host galaxy properties and find that the velocity kurtosis and the slope of their velocity dispersion profiles is different between the two GC subpopulations in more massive galaxies.
Extended stellar clusters with effective radii larger than 10 pc have been found in various environments. Objects with masses comparable to globular clusters (GCs) are called extended clusters (ECs), while objects with masses in the dwarf galaxy regime are called ultra-compact dwarf galaxies (UCDs). The paper analyses the observational parameters luminosity, effective radius, and projected distance to the host galaxy, of all known ECs and UCDs and the dependence of these parameters on the type and the luminosity of their host galaxy. We searched the available literature to compile a catalog of star clusters larger than 10 pc. As there is no clear distinction between ECs and UCDs, both types of objects will be called extended stellar objects (EOs). In total, we found 813 EOs of which 171 are associated with late-type and 642 with early-type galaxies. EOs cover a luminosity range from about MV = -4 to -14 mag. However, the vast majority of EOs brighter than -10 mag are associated with elliptical galaxies. At each magnitude EOs are found with effective radii between 10 pc and an upper size limit, which shows a clear trend: the more luminous the object the larger is the upper size limit. For EOs associated with early-and late-type galaxies, the luminosity functions peak at -6.40 and -6.47 mag, respectively, which is about one magnitude fainter than the peak of the GC luminosity function. EOs and GCs form a coherent structure in the reff vs. MV parameter space, while there is a clear gap between EOs and early type dwarf galaxies. However, there is a small potential overlap at the high-mass end, where the most extended EOs are close to the parameters of compact elliptical galaxies. We compare the EO sample with numerical models and conclude that the parameters of the EO sample as a whole can be very well explained by a star cluster origin, where EOs are the results of merged cluster complexes.
I have combined the Emsellem et al. ATLAS3D rotation measures of a large sample of early-type galaxies with HST-based classifications of their central structure to characterize the rotation velocities of galaxies with cores. "Core galaxies" rotate slowly, while "power-law galaxies" (galaxies that lack cores) rotate rapidly, confirming the analysis of Faber et al. Significantly, the amplitude of rotation sharply discriminates between the two types in the -19 > Mv > -22 domain over which the two types coexist. The slow rotation in the small set of core galaxies with Mv > -20, in particular, brings them into concordance with the more massive core galaxies. The ATLAS3D "fast-rotating" and "slow-rotating" early-type galaxies are essentially the same as power-law and core galaxies, respectively, or the Kormendy & Bender two families of elliptical galaxies based on rotation, isophote shape, and central structure. The ATLAS3D fast rotators do include roughly half of the core galaxies, but their rotation-amplitudes are always at the lower boundary of that subset. Essentially all core galaxies have ATLAS3D rotation-amplitudes lambda_(R_e/2) <= 0.25, while all galaxies with lambda_(R_e/2) > 0.25 and figure eccentricity > 0.2 lack cores. Both figure rotation and the central structure of early-type galaxies should be used together to separate systems that appear to have formed from "wet" versus "dry" mergers.
Galaxy scaling relations, which describe a connection between ostensibly unrelated physical characteristics of galaxies, testify to an underlying order in galaxy formation that requires understanding. I review the development of a scaling relation that 1) unites the well-known Fundamental Plane (FP) relation of giant elliptical galaxies and Tully-Fisher (TF) relation of disk galaxies, 2) fits low mass spheroidal galaxies, including the ultra-faint satellites of our Galaxy, 3) explains the apparent shift of lenticular (S0) galaxies relative to both FP or TF, 3) describes all stellar dynamical systems, including systems with no dark matter (stellar clusters), 4) associates explicitly the numerical coefficients that account for the apparent "tilt" of the FP away from the direct expectation drawn from the virial theorem with systematic variations in the total mass-to-light ratio of galaxies within the half-light radius, 5) connects with independent results that demonstrate the robustness of mass estimators when applied at the half-light radius, and 6) results in smaller scatter for disk galaxies than the TF relation. The relation develops naturally from the virial theorem, but implies the existence of additional galaxy formation physics that must now be a focus of galaxy formation studies. More pragmatically, the relation provides a lynchpin that can be used to measure distances and galaxy masses. I review two applications: 1) the cross-calibration of distance measurement methods, and 2) the determination of mass-to-light ratios of simple stellar populations as a function of age, and implications of the latter for the stellar initial mass function.
We present the results of SCUBA2 observations at 450 micron and 850 micron of the field lensed by the massive cluster A370. With a total survey area > 100 arcmin2 and 1 sigma sensitivities of 3.92 and 0.82 mJy/beam at 450 and 850 micron respectively, we find a secure sample of 20 sources at 450 micron and 26 sources at 850 micron with a signal-to-noise ratio > 4. Using the latest lensing model of A370 and Monte Carlo simulations, we derive the number counts at both wavelengths. The 450 micron number counts probe a factor of four deeper than the counts recently obtained from the Herschel Space Telescope at similar wavelengths, and we estimate that ~47-61% of the 450 micron extragalactic background light (EBL) resolved into individual sources with 450 micron fluxes greater than 4.5 mJy. The faint 450 micron sources in the 4 sigma sample have positional accuracies of 3 arcseconds, while brighter sources (signal-to-noise > 6 sigma) are good to 1.4 arcseconds. Using the deep radio map (1 sigma ~ 6 uJy) we find that the percentage of submillimeter sources having secure radio counterparts is 85% for 450 micron sources with intrinsic fluxes > 6 mJy and 67% for 850 micron sources with intrinsic fluxes > 4 mJy. We also find that 67% of the > 4 sigma 450 micron sources are detected at 850 micron, while the recovery rate at 450 micron of > 4 sigma 850 micron sources is 54%. Combined with the source redshifts estimated using millimetric flux ratios, the recovered rate is consistent with the scenario where both 450 micron and 20 cm emission preferentially select lower redshift dusty sources, while 850 micron emission traces a higher fraction of dusty sources at higher redshifts. [Abridge]
We introduce a new method to calculate the multi-scale 3D filamentation of SDSS DR5 galaxy clusters and also applied it to N-body simulations. We compared the filamentation of the observed vs. mock samples in metric space on scales from 8 Mpc to 30 Mpc. Mock samples are closer to the observed sample than random samples, and one of the mock samples behaves better than another one. We also find that the observed sample has a large filamentation value at a scale of 10 Mpc, which is not found from either mock samples or random samples. Key words: filamentation, metric space, galaxy clusters, SDSS DR5.
The induction equation induces non trivial correlations between the primordial curvature mode and the magnetic mode which is a non linear effect. Assuming a stochastic, gaussian magnetic field the resulting power spectra determining the two point cross correlation functions between the primordial curvature perturbation and the magnetic energy density contrast as well as the magnetic anisotropic stress are calculated approximately. The corresponding numerical solutions are used to calculate the angular power spectra determining the temperature anisotropies and polarization of the cosmic microwave background, $C_{\ell}$. It is found that the resulting $C_{\ell}$ are sub-leading in comparison to those generated by the compensated mode for a magnetic field which only redshifts with the expansion of the universe.The main focus are scalar modes, however, vector modes will also be briefly discussed.
We present the first measurement of the large-scale cross-correlation of Lyman alpha forest absorption and Damped Lyman alpha systems (DLA), using the 9th Data Release of the Baryon Oscillation Spectroscopic Survey (BOSS). The cross-correlation is clearly detected on scales up to 40 Mpc/h and is well fitted by the linear theory prediction of the standard Cold Dark Matter model of structure formation with the expected redshift distortions, confirming its origin in the gravitational evolution of structure. The amplitude of the DLA-Lyman alpha cross-correlation depends on only one free parameter, the bias factor of the DLA systems, once the Lyman alpha forest bias factors are known from independent Lyman alpha forest correlation measurements. We measure the DLA bias factor to be b_D = (2.17 +/- 0.20) beta_F^{0.22}, where the Lyman alpha forest redshift distortion parameter beta_F is expected to be above unity. This bias factor implies a typical host halo mass for DLAs that is much larger than expected in present DLA models, and is reproduced if the DLA cross section scales with halo mass as M_h^alpha, with alpha= 1.1 +/- 0.1 for beta_F=1. Matching the observed DLA bias factor and rate of incidence requires that atomic gas remains extended in massive halos over larger areas than predicted in present simulations of galaxy formation, with typical DLA proper sizes larger than 20 kpc in host halos of masses ~ 10^12 solar masses. We infer that typical galaxies at z ~ 2 to 3 are surrounded by systems of atomic clouds that are much more extended than the luminous parts of galaxies and contain ~ 10% of the baryons in the host halo.
The singularity for the big bang state can be represented using the generalized anisotropic Friedmann equation, resulting in a system of differential equations in a central force field. We study the regularizability of this singularity as a function of a parameter, the equation of state, $w$. We prove that for $w >1$ it is regularizable only for $w$ satisfying relative prime number conditions, and for $w \leq 1$ it can always be regularized. This is done by using a McGehee transformation, usually applied in the three and four-body problems. This transformation blows up the singularity into an invariant manifold. The relationship of this result to other cosmological models is briefly discussed.
Supernovae observations strongly support the presence of a cosmological constant, but its value, which we will call apparent, is normally determined assuming that the universe can be accurately described by a homogeneous model. Even in the presence of a cosmological constant we cannot exclude nevertheless the presence of a small local inhomogeneity which could affect the apparent value of the cosmological constant. Neglecting the presence of the inhomogeneity can in fact introduce a systematic misinterpretation of cosmological data, leading to the distinction between an apparent and the true value of the cosmological constant. But is such a difference distinguishable? Recently we set out to model the local inhomogeneity with a {\Lambda}LTB solution and computed the relation between the apparent and the true value of the cosmological constant. In this essay we reproduce the essence of our model with the emphasis on its physical implications.
One of the most intriguing scenarios proposed to explain how active galactic nuclei are triggered involves the existence of a supermassive binary black hole system in their cores. Here we present an observational evidence for the first spectroscopically resolved sub-parsec orbit of a such system in the core of Seyfert galaxy NGC 4151. Using a method similar to those typically applied for spectroscopic binary stars we obtained radial velocity curves of the supermassive binary system, from which we calculated orbital elements and made estimates about the masses of components. Our analysis shows that periodic variations in the light and radial velocity curves can be accounted for an eccentric, sub-parsec Keplerian orbit of a 15.9-year period. The flux maximum in the lightcurve correspond to the approaching phase of a secondary component towards the observer. According to the obtained results we speculate that the periodic variations in the observed H{\alpha} line shape and flux are due to shock waves generated by the supersonic motion of the components through the surrounding medium. Given the large observational effort needed to reveal this spectroscopically resolved binary orbital motion we suggest that many such systems may exist in similar objects even if they are hard to find. Detecting more of them will provide us with insight into black hole mass growth process.
We look for possible spectral features and systematic effects in Fermi-LAT publicly available high-energy gamma-ray data by studying photons from the Galactic centre, nearby galaxy clusters, nearby brightest galaxies, AGNs, unassociated sources, hydrogen clouds and Earth Limb. Apart from already known 130 GeV gamma-ray excesses from the first two sources, we find no new statistically significant signal from others. Much of our effort goes to studying Earth Limb photons. In the energy range 30 GeV to 200 GeV the Earth Limb gamma-ray spectrum follows power-law with spectral index 2.87\pm 0.04 at 95 % CL, in a good agreement with the PAMELA measurement of cosmic ray proton spectral index between 2.82-2.85, confirming the physical origin of the Limb gamma-rays. In small subsets of Earth Limb data with small photon incidence angle it is possible to obtain spectral features at different energies, including at 130 GeV, but determination of background, thus their significances, has large uncertainties in those cases. We observe systematic 2\sigma level differences in the Earth Limb spectra of gamma-rays with small and large incidence angles. The behaviour of those spectral features as well as background indicates that they are likely statistical fluctuations.
The purpose of our study is to understand the mathematical origin in real space of modulated and damped sinusoidal peaks observed in cosmic microwave background radiation anisotropies. We use the theory of the Fourier transform to connect localized features of the two-point correlation function in real space to oscillations in the power spectrum. We also illustrate analytically and by means of Monte Carlo simulations the angular correlation function for distributions of filled disks with fixed or variable radii capable of generating oscillations in the power spectrum. While the power spectrum shows repeated information in the form of multiple peaks and oscillations, the angular correlation function offers a more compact presentation that condenses all the information of the multiple peaks into a localized real space feature. We have seen that oscillations in the power spectrum arise when there is a discontinuity in a given derivative of the angular correlation function at a given angular distance. These kinds of discontinuities do not need to be abrupt in an infinitesimal range of angular distances but may also be smooth, and can be generated by simply distributing excesses of antenna temperature in filled disks of fixed or variable radii on the sky, provided that there is a non-null minimum radius and/or the maximum radius is constrained.
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