We take advantage of the sensitivity and resolution of the Herschel Space Observatory at 100 and 160 mum to directly image the thermal dust emission and investigate the infrared luminosities (LsubIR) ...and dust obscuration of typical star-forming (L*) galaxies at high redshift. The result is similar to that inferred from previous investigations of the UV, Halpha, 24 mum, radio, and X-ray properties of the same galaxies studied here. Stacking in bins of UV slope (beta) implies that L* galaxies with redder spectral slopes are also dustier and that the correlation between beta and dustiness is similar to that found for local starburst galaxies. Hence, the rest-frame ~30 and 50 mum fluxes validate on average the use of the local UV attenuation curve to recover the dust attenuation of typical star-forming galaxies at high redshift.
We follow the galaxy stellar mass assembly by morphological and spectral type in the COSMOS 2 deg2 field. We derive the stellar mass functions and stellar mass densities from z = 2 to z = 0.2 using ...196,000 galaxies selected at F 3.6 μm > 1 μJy with accurate photometric redshifts (σ_{(z_phot-z_spec)/(1+z_spec)}=0.008 at i + < 22.5). Using a spectral classification, we find that z ~ 1 is an epoch of transition in the stellar mass assembly of quiescent galaxies. Their stellar mass density increases by 1.1 dex between z = 1.5-2 and z = 0.8-1 (Δt ~ 2.5 Gyr), but only by 0.3 dex between z = 0.8-1 and z ~ 0.1 (Δt ~ 6 Gyr). Then, we add the morphological information and find that 80%-90% of the massive quiescent galaxies (log M ∼ 11) have an elliptical morphology at z < 0.8. Therefore, a dominant mechanism links the shutdown of star formation and the acquisition of an elliptical morphology in massive galaxies. Still, a significant fraction of quiescent galaxies present a Spi/Irr morphology at low mass (40%-60% at log M∼ 9.5), but this fraction is smaller than predicted by semi-analytical models using a "halo quenching" recipe. We also analyze the evolution of star-forming galaxies and split them into "intermediate activity" and "high activity" galaxies. We find that the most massive "high activity" galaxies end their high star formation rate phase first. Finally, the space density of massive star-forming galaxies becomes lower than the space density of massive elliptical galaxies at z < 1. As a consequence, the rate of "wet mergers" involved in the formation of the most massive ellipticals must decline very rapidly at z < 1, which could explain the observed slow down in the assembly of these quiescent and massive sources. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555. Also based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407. Also based on data collected at: the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; the XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA; the European Southern Observatory under Large Program 175.A-0839, Chile; Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, and the National Optical Astronomy Observatory, which are operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation; and the Canada-France-Hawaii Telescope with MegaPrime/MegaCam operated as a joint project by the CFHT Corporation, CEA/DAPNIA, the NRC and CADC of Canada, the CNRS of France, TERAPIX, and the University of Hawaii.
The VLA-COSMOS Large Project is described and Its scientific objective is discussed. We present a catalog of similar to 3600 radio sources found in the 2 deg super(2) COSMOS field at 1.4 GHz. The ...observations in the VLA A and C configuration resulted in a resolution of 1.5" x 1.4" and a mean rms noise of similar to 10.5 (15) mu Jy beam super(-1) in the central 1 (2) deg super(2). Eighty radio sources are clearly extended consisting of multiple components, and most of them appear to be double-lobed radio galaxies. The astrometry of the catalog has been thoroughly tested, and the uncertainty in the relative and absolute astrometry are 130 and <55 mas, respectively.
ABSTRACT
In this work, we study the intracluster medium (ICM) of a galaxy cluster at the cosmic noon: JKCS 041 at z = 1.803. A 28 h long Sunyaev-Zel’dovich (SZ) observation using MUSTANG-2 allows us ...to detect JKCS 041, even if intrinsically extremely faint compared to other SZ-detected clusters. We found that the SZ peak is offset from the X-ray centre by about 220 kpc in the direction of the brightest cluster galaxy, which we interpret as due to the cluster being observed just after the first passage of a major merger. JKCS 041 has a low central pressure and a low Compton Y compared to local clusters selected by their ICM, likely because the cluster is still in the process of assembly but also in part because of a hard-to-quantify bias in current local ICM-selected samples. JKCS 041 has a 0.5 dex fainter Y signal than another less massive z ∼ 1.8 cluster, exemplifying how much different weak-lensing mass and SZ mass can be at high redshift. The observations we present provide us with the measurement of the most distant resolved pressure profile of a galaxy cluster. Comparison with a library of plausibly descendants shows that JKCS 041 pressure profile will likely increase by about 0.7 dex in the next 10 Gyr at all radii.
Aims. We compute photometric redshifts in the fourth public release of the Canada-France-Hawaii Telescope Legacy Survey. This unique multi-colour catalogue comprises $u^*, g', r', i', z'$ photometry ...in four deep fields of 1 deg2 each and 35 deg2 distributed over three wide fields. Methods. We used a template-fitting method to compute photometric redshifts calibrated with a large catalogue of 16 983 high-quality spectroscopic redshifts from the VVDS-F02, VVDS-F22, DEEP2, and the zCOSMOS surveys. The method includes correction of systematic offsets, template adaptation, and the use of priors. We also separated stars from galaxies using both size and colour information. Results. Comparing with galaxy spectroscopic redshifts, we find a photometric redshift dispersion, $\sigma_{\Delta z/(1+z_{\rm s})}$, of 0.028–0.30 and an outlier rate, $|\Delta z| \ge 0.15\times (1+z_{\rm s})$, of 3–4% in the deep field at $i'_{\rm AB}$ < 24. In the wide fields, we find a dispersion of 0.037–0.039 and an outlier rate of 3–4% at $i'_{\rm AB}$ < 22.5. Beyond $i'_{\rm AB}$ = 22.5 in the wide fields the number of outliers rises from 5% to 10% at $i'_{\rm AB}$ < 23 and $i'_{\rm AB}$ < 24, respectively. For the wide sample the systematic redshift bias stays below 1% to $i'_{\rm AB}$ < 22.5, whereas we find no significant bias in the deep fields. We investigated the effect of tile-to-tile photometric variations and demonstrated that the accuracy of our photometric redshifts is reduced by at most 21%. Application of our star-galaxy classifier reduced the contamination by stars in our catalogues from 60% to 8% at $i'_{\rm AB}$ < 22.5 in our field with the highest stellar density while keeping a complete galaxy sample. Our CFHTLS T0004 photometric redshifts are distributed to the community. Our release includes 592891 ($i'_{\rm AB}$ < 22.5) and 244701 ($i'_{\rm AB}$ < 24) reliable galaxy photometric redshifts in the wide and deep fields, respectively.
We study relationships between star-formation rate (SFR) and the accretion luminosity and nuclear obscuration of X-ray selected active galactic nuclei (AGNs) using a combination of deep far-infrared ...(FIR) and X-ray data in three key extragalactic survey fields (GOODS-South, GOODS-North and COSMOS), as part of the PACS Evolutionary Probe (PEP) program. The use of three fields with differing areas and depths enables us to explore trends between the global FIR luminosity of the AGN hosts and the luminosity of the active nucleus across 4.5 orders of magnitude in AGN luminosity (LAGN) and spanning redshifts from the Local Universe to z = 2.5. Using imaging from the Herschel/PACS instrument in 2−3 bands, we combine FIR detections and stacks of undetected objects to arrive at mean fluxes for subsamples in bins of redshift and X-ray luminosity. We constrain the importance of AGN-heated dust emission in the FIR and confirm that the majority of the FIR emission of AGNs is produced by cold dust heated by star-formation in their host galaxies. We uncover characteristic trends between the mean FIR luminosity (L60) and accretion luminosity of AGNs, which depend both on LAGN and redshift. At low AGN luminosities, accretion and SFR are uncorrelated at all redshifts, consistent with a scenario where most low-luminosity AGNs are primarily fueled by secular processes in their host galaxies. At high AGN luminosities, a significant correlation is observed between L60 and LAGN, but only among AGNs at low and moderate redshifts (z < 1). We interpret this observation as a sign of the increasing importance of major-mergers in driving both the growth of super-massive black holes (SMBHs) and global star-formation in their hosts at high AGN luminosities. We also find evidence that the enhancement of SFR in luminous AGNs weakens or disappears at high redshifts (z > 1) suggesting that the role of mergers is less important at these epochs. At all redshifts, we find essentially no relationship between L60 and nuclear obscuration across five orders of magnitude in obscuring Hydrogen column density (NH), suggesting that various mechanisms are likely to be responsible for obscuring X-rays in active galaxies. We discuss a broad scenario which can account for these trends: one in which two different modes of AGN fueling operate in the low- and high-luminosity regimes of SMBH accretion. We postulate that the dominant mode of accretion among high-luminosity AGNs evolves with redshift. Our study, as well as a body of evidence from the literature and emerging knowledge about the properties of high redshift galaxies, supports this scenario.
We present new Atacama Large Millimeter Array (ALMA) dust continuum observations of 101 galaxies in the COSMOS field to study the effect of the environment on the interstellar medium at z ∼ 0.7. At ...this redshift, our targets span a wide range of environments allowing for a diverse sample of galaxies with densities of = 0.16-10.5 Mpc−2 (per Δz = 0.024). Using the ALMA observations, we calculate the total interstellar medium (ISM) mass (MISM) and look for depletion as a function of galaxy density in order to understand the quenching or triggering of star formation in galaxies in different environments. MISM is found to have a small dependence on the environment, while the depletion timescale remains constant (∼200 Myr) across all environments. We find elevated MISM values at intermediate densities and lower values at high densities compared to low (field) densities. Our observed evolution in gas fraction with density in this single redshift slice is equivalent to the observed evolution with cosmic time over 2-3 Gyr. To explain the change in the gas mass fraction seen in galaxies in intermediate and high densities, these results suggest environmental processes such as mergers and ram pressure stripping are likely playing a role in dense filamentary cluster environments.
Large-scale structures (LSSs) out to z < 3.0 are measured in the Cosmic Evolution Survey (COSMOS) using extremely accurate photometric redshifts (photoz). The K sub(s)-band-se lected sample (from ...Ultra-Vista) is comprised of 155,954 galaxies. Two techniques-adaptive smoothing and Voronoi tessellation-are used to estimate the environmental densities within 127 redshift slices. Approximately 250 statistically significant overdense structures are identified out to z = 3.0 with shapes varying from elongated filamentary structures to more circularly symmetric concentrations. We also compare the densities derived for COSMOS with those based on semi-analytic predictions for a LambdaCDM simulation and find excellent overall agreement between the mean densities as a function of redshift and the range of densities. The galaxy properties (stellar mass, spectral energy distributions (SEDs), and star formation rates (SFRs)) are strongly correlated with environmental density and redshift, particularly at z < 1.0-1.2. Classifying the spectral type of each galaxy using the rest-frame b - i color (from the photoz SED fitting), we find a strong correlation of early-type galaxies (E-Sa) with high-density environments, while the degree of environmental segregation varies systematically with redshift out to z ~ 1.3. In the highest density regions, 80% of the galaxies are early types at z = 0.2 compared to only 20% at z = 1.5. The SFRs and the star formation timescales exhibit clear environmental correlations. At z > 0.8, the SFR density is uniformly distributed over all environmental density percentiles, while at lower redshifts the dominant contribution is shifted to galaxies in lower density environments.
We present the Zurich Extragalactic Bayesian Redshift Analyzer (zebra). The current version of zebra combines and extends several of the classical approaches to produce accurate photometric redshifts ...down to faint magnitudes. In particular, zebra uses the template-fitting approach to produce Maximum Likelihood and Bayesian redshift estimates based on the following points.
An automatic iterative technique to correct the original set of galaxy templates to best represent the Spectral Energy Distributions (SEDs) of real galaxies at different redshifts.
A training set of spectroscopic redshifts for a small fraction of the photometric sample to improve the robustness of the photometric redshift estimates.
An iterative technique for Bayesian redshift estimates, which extracts the full two-dimensional redshift and template probability function for each galaxy.
We demonstrate the performance of zebra by applying it to a sample of 866 I
AB
≤ 22.5 COSMOS galaxies with available u*, B, V, g′, r′, i′, z′ and K
s
photometry and zCOSMOS spectroscopic redshifts in the range 0 < z < 1.3. Adopting a 5σ clipping that excludes ≤10 galaxies, both the Maximum Likelihood and Bayesian zebra estimates for this sample have an accuracy σΔz/(1+z) smaller than 0.03. Similar accuracies are recovered using mock galaxies.
zebra is made available at http://www.exp-astro.phys.ethz.ch/ZEBRA.
We describe the details of the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) Wide Field Channel (WFC) observations of the COSMOS field, including the data calibration and processing ...procedures. We obtained a total of 583 orbits of HST ACS/WFC Imaging in the F814W filter, covering a field that is 1.64 deg super(2) in area, the largest contiguous field ever Imaged with HST. The median exposure depth across the field is 2028 s (one HST orbit), achieving a limiting point-source depth AB(F814W) = 27.2 (5 sigma ). we also present details of the astrometric image registration and distortion removal and image combination using MultiDrizzle, motivating the choice of our final pixel scale (30 mas pixel super(-1)), based on the requirements for weak-lensing science. The final set of images are publicly available through the archive sites at IPAC and STScI, along with further documentation on how they were produced.
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