We present the first set of XMM-Newton EPIC observations in the 2 deg super(2) COSMOS field. The strength of the COSMOS project is the unprecedented combination of a large solid angle and sensitivity ...over the whole multiwavelength spectrum. The XMM-Newtc observations are very efficient in localizing and identifying active galactic nuclei (AGNs) and clusters, as well as groups of galaxies. One of the primary goals of the XMM-Newton Cosmos survey is to study the coevolution of active galactic nuclei as a function of their environment in the cosmic web. Here we present the log of observations, images, and a summary of first research highlights for the first pass of 25 XMM-Newton pointings across the field. In the existing data set we have detected 1416 new X-ray sources in the 0.5-2, 2-4.5, and 4.5-10 keV bands to an equivalent 0.5-2 keV flux limit of 7 x 10 super(-16) erg cm super(-2)s super(-1). The number of sources is expected to grow to almost 2000 in the final coverage of the survey. From an X-ray color-color analysis we identify a population of heavily obscured, partially leaky or reflecting absorbers, most of which are likely to be nearby, Compton-thick AGNs.
We investigate of the properties of ~2000 Herschel/SPIRE far-infrared-selected galaxies from 0 <z< 4 in the CFHTLS-D1 field. Using a combination of extensive spectroscopy from the VVDS and ORELSE ...surveys, deep multiwavelength imaging from CFHT, VLA, Spitzer, XMM-Newton, and Herschel, and well-calibrated spectral energy distribution fitting, Herschel-bright galaxies are compared to optically-selected galaxies at a variety of redshifts. Herschel-selected galaxies are observed to span a range of stellar masses, colors, and absolute magnitudes equivalent to galaxies undetected in SPIRE. Though many Herschel galaxies appear to be in transition, such galaxies are largely consistent with normal star-forming galaxies when rest-frame colors are utilized. The nature of the star-forming “main sequence” is studied and we warn against adopting this framework unless the main sequence is determined precisely. Herschel galaxies at different total infrared luminosities (LTIR) are compared. Bluer optical colors, larger nebular extinctions, and larger contributions from younger stellar populations are observed for galaxies with larger LTIR, suggesting that low-LTIR galaxies are undergoing rejuvenated starbursts while galaxies with higher LTIR are forming a larger percentage of their stellar mass. A variety of methods are used to select powerful active galactic nuclei (AGN). Galaxies hosting all types of AGN are observed to be undergoing starbursts more commonly and vigorously than a matched sample of galaxies without powerful AGN and, additionally, the fraction of galaxies with an AGN increases with increasing star formation rate at all redshifts. At all redshifts (0 <z< 4) the most prodigious star-forming galaxies are found to contain the highest fraction of powerful AGN. For redshift bins that allow a comparison (z> 0.5), the highest LTIR galaxies in a given redshift bin are unobserved by SPIRE at subsequently lower redshifts, a trend linked to downsizing. In conjunction with other results, this evidence is used to argue for prevalent AGN-driven quenching in starburst galaxies across cosmic time.
We present an analysis of the stellar mass growth over the last 10 Gyr ($z\le 2$) using a unique large sample of galaxies selected at $3.6~\mu$m. We have assembled accurate photometric and ...spectroscopic redshifts for ~21 200 and 1500 galaxies, respectively, with F(3.6 μm) ≥ 9.0 μJy by combining data from Spitzer-SWIRE IRAC, the VIMOS VLT Deep Survey (VVDS), UKIDSS and very deep optical CFHTLS photometry. We split our sample into quiescent (red) and active (blue) galaxies on the basis of an SED fitting procedure that we have compared with the strong rest-frame color bimodality $(NUV-r')_{\rm ABS}$. The present sample contains ~ 4400 quiescent galaxies. Our measurements of the K-rest frame luminosity function and luminosity density evolution support the idea that a large fraction of galaxies is already assembled at z ~ 1.2, with almost 80% and 50% of the active and quiescent populations already in place, respectively. Based on the analysis of the evolution of the stellar mass-to-light ratio (in K-band) for the spectroscopic sub-sample, we derive the stellar mass density for the entire sample. We find that the global evolution of the stellar mass density is well reproduced by the star formation rate derived from UV based measurements when an appropriate dust correction is applied, which supports the idea of an initial mass function that is on average universal. Over the last 8 Gyr (z ≤ 1.2) we observe that the stellar mass density of the active population shows a modest mass growth rate ($\dot{\rho}$ ~ 0.005(±0.005) $M_{\odot}$/Mpc3/yr), consistent with a constant stellar mass density, $\rho_{\star}^{\rm active}$ ~ 3.1 $\times$ 108 $M_{\odot}$/Mpc3. In contrast, an increase by a factor of ~2 for the quiescent population over the same timescale is observed. As a consequence, the growth of the stellar mass in the quiescent population must be due to the shutoff of star formation in active galaxies that migrate into the quiescent population. We estimate this stellar mass flux to be $\dot{\rho}_{A\rightarrow Q}$ ~ 0.017(±0.004) $M_{\odot}$/Mpc3/yr, which balances the major fraction of new stars born according to our best SFR estimate ($\dot{\rho}$ = 0.025(±0.003) $M_{\odot}$/Mpc3/yr). From $z = 2$ to $z = 1.2$, we observe a major build-up of the quiescent population with an increase by a factor of ~10 in stellar mass (a mass growth rate of ~ 0.063 $M_{\odot}$/Mpc3/yr). This rapid evolution suggests that we are observing the epoch when, for the first time in the history of the universe, an increasing fraction of galaxies end their star formation activity and start to build up the red sequence.
Context. For more than two decades we have known that galaxy morphological segregation is present in the Local Universe. It is important to see how this relation evolves with cosmic time. Aims. To ...investigate how galaxy assembly took place with cosmic time, we explore the evolution of the morphology-density relation up to redshift z ~ 1 using about 10 000 galaxies drawn from the zCOSMOS Galaxy Redshift Survey. Taking advantage of accurate HST/ACS morphologies from the COSMOS survey, of the well-characterised zCOSMOS 3D environment, and of a large sample of galaxies with spectroscopic redshift, we want to study here the evolution of the morphology-density relation up to z ~ 1 and its dependence on galaxy luminosity and stellar mass. The multi-wavelength coverage of the field also allows a first study of the galaxy morphological segregation dependence on colour. We further attempt to disentangle between processes that occurred early in the history of the Universe or late in the life of galaxies. Methods. The zCOSMOS field benefits of high-resolution imaging in the F814W filter from the Advanced Camera for Survey (ACS). We use standard morphology classifiers, optimised for being robust against band-shifting and surface brightness dimming, and a new, objective, and automated method to convert morphological parameters into early, spiral, and irregular types. We use about 10 000 galaxies down to IAB = 22.5 with a spectroscopic sampling rate of 33% to characterise the environment of galaxies up to z ~ 1 from the 100 kpc scales of galaxy groups up to the 100 Mpc scales of the cosmic web. The evolution of the morphology-density relation in different environments is then studied for luminosity and stellar-mass selected, volume-limited samples of galaxies. The trends are described and related to the various physical processes that could play a relevant role in the build-up of the morphology-density relation. Results. We confirm that the morphological segregation is present up to z ~ 1 for luminosity-selected, volume-limited samples. The behaviour of the morphology-density relation gets flatter at fixed masses expecially above 1010.6 $M_{\odot}$. We suggest the existence of a critical mass above which the physical processes governing galaxy stellar mass also determine the shaping of the galaxy more than its environment. We finally show that at a fixed morphology there is still a residual variation in galaxy colours with density. Conclusions. The observed evolution with redshift of the morphology-density relation offers an opportunity to trace the effect of nature and nurture as a function of environment. Even though it is based mainly on a biased view, the environmental dependence of the morphological evolution for luminosity-selected, volume-limited samples seems to indicate that nurture is in play. On the other hand, the lack of evolution observed for early-type and spiral galaxies that are more massive than 1010.8 $M_{\odot}$ independents of the environment indicates that nature has imprinted these properties early in the life of these galaxies. We conclude that the relative contribution of nature and nurture in different environments strongly depends on the mass of galaxies, consistent with a downsizing scenario.
We present a study of the host galaxies of active galactic nucleus (AGN) selected from the zCOSMOS survey to establish if accretion onto supermassive black holes (SMBHs) and star formation are ...explicitly linked up to z ~ 1. We identify 152 galaxies that harbor AGN, based on their X-ray emission (L 0.5-10 keV>1042 erg s-1) detected by XMM-Newton observations of 7543 galaxies (i acs < 22.5). Star formation rates (SFRs), including those weighted by stellar mass, of a subsample are determined using the O IIl3727 emission-line luminosity, corrected for an AGN contribution based on the observed O IIIl5007 strength or that inferred by their hard (2-10 keV) X-ray luminosity. We find that an overwhelming majority of AGN host galaxies have significant levels of star formation with a distribution spanning ~1-100 M yr-1; their average SFR is higher than that of galaxies with equivalent stellar mass (M *>4 X 1010 M ). The close association between AGN activity and star formation is further substantiated by an increase in the fraction of galaxies hosting AGN with the youthfulness of their stars as indicated by the rest-frame color (U-V) and spectral index Dn (4000); we demonstrate that a mass-selected sample is required to alleviate an artificial peak in the AGN fraction falling in the transition region due to the fact that many 'blue cloud' galaxies have low mass-to-light ratios in luminosity-limited samples. We also find that the SFRs of AGN hosts evolve with cosmic time in a manner that closely mirrors the overall galaxy population and naturally explains the low SFRs in AGNs (z < 0.3) from the SDSS. We conclude that the conditions most conducive for AGN activity are a massive host galaxy and a large reservoir of gas. Furthermore, a direct correlation between mass-accretion rate onto SMBHs and SFR is shown to be weak although the average ratio (~10-2) is constant with redshift, effectively shifting the evidence for a co-evolution scenario in a statistical manner to smaller physical scales (i.e., within the same galaxies). The order-of-magnitude increase in this ratio compared to the locally measured value of M BH/M bulge is consistent with an AGN lifetime substantially shorter than that of star formation. Our findings illustrate an intermittent scenario with underlying complexities regarding fueling over vastly different physical (and temporal) scales yet to be firmly determined.
The contribution of the merging process to the early phase of galaxy assembly at z > 1 and, in particular, to the build-up of the red sequence, still needs to be accurately assessed. We aim to ...measure the major merger rate of star-forming galaxies at 0.9 < z < 1.8, using close pairs identified from integral field spectroscopy (IFS). Merging of star-forming galaxies is frequent at around the peak in star formation activity. Our results show that gasrich mergers make an important contribution to the growth of massive galaxies since z ~1.5, particularly on the build-up of the red sequence.
Context. Cosmological parameters can be constrained by counting clusters of galaxies as a function of mass and redshift and by considering regions of the sky sampled as deeply and as homogeneously as ...possible. Aims. Several methods for detecting clusters in large imaging surveys have been developed, among which the one used here, which is based on detecting structures. This method was first applied to the Canada France Hawaii Telescope Legacy Survey (CFHTLS) Deep 1 field by Mazure et al. (2007, A&A, 467, 49), then to all the Deep and Wide CFHTLS fields available in the T0004 data release by Adami et al. (2010, A&A, 509, A81). The validity of the cluster detection rate was estimated by applying the same procedure to galaxies from the Millennium simulation. Here we use the same method to analyse the full CFHTLS Wide survey, based on the T0006 data release. Methods. Our method is based on the photometric redshifts computed with Le Phare for all the galaxies detected in the Wide fields, limited to magnitudes z′ ≤ 22.5. We constructed galaxy density maps in photometric redshift bins of 0.1 based on an adaptive kernel technique, detected structures with SExtractor at various detection levels, and built cluster catalogues by applying a minimal spanning tree algorithm. Results. In a total area of 154 deg2, we have detected 4061 candidate clusters at 3σ or above (6802 at 2σ and above), in the redshift range 0.1 ≤ z ≤ 1.15, with estimated mean masses between 1.3 × 1014 and 12.6 × 1014 M⊙. This catalogue of candidate clusters will be available at the CDS. We compare our detections with those made in various CFHTLS analyses with other methods. By stacking a subsample of clusters, we show that this subsample has typical cluster characteristics (colour − magnitude relation, galaxy luminosity function). We also confirm that the cluster-cluster correlation function is comparable to the one obtained for other cluster surveys and analyse large-scale filamentary galaxy distributions. Conclusions. We have increased the number of known optical high-redshift cluster candidates by a large factor, an important step towards obtaining reliable cluster counts to measure cosmological parameters. The clusters that we detect behave as expected if they are located at the intersection of filaments by which they are fed.
The WIRCam Ultra Deep Survey (WUDS) Pelló, R.; Hudelot, P.; Laporte, N. ...
Astronomy and astrophysics (Berlin),
12/2018, Letnik:
620
Journal Article
Recenzirano
Odprti dostop
The aim of this paper is to introduce the WIRCam Ultra Deep Survey (WUDS), a near-IR photometric survey carried out at the CFH Telescope in the field of the CFHTLS-D3 field (Groth Strip). WUDS ...includes four near-IR bands (Y, J, H and Ks) over a field of view of ∼400 arcmin2. The typical depth of WUDS data reaches between ∼26.8 in Y and J, and ∼26 in H and Ks (AB, 3σ in 1.3″ aperture), whereas the corresponding depth of the CFHTLS-D3 images in this region ranges between 28.6 and 29 in ugr, 28.2 in i and 27.1 in z (same S/N and aperture). The area and depth of this survey were specifically tailored to set strong constraints on the cosmic star formation rate and the luminosity function brighter or around L⋆ in the z ∼ 6 − 10 redshift domain, although these data are also useful for a variety of extragalactic projects. This first paper is intended to present the properties of the public WUDS survey in details: catalog building, completeness and depth, number counts, photometric redshifts, and global properties of the galaxy population. We have also concentrated on the selection and characterization of galaxy samples at z ∼ 4.5 − 7 in this field. For these purposes, we include an adjacent shallower area of ∼1260 arcmin2 in this region, extracted from the WIRCam Deep Survey (WIRDS), and observed in J, H and Ks bands. UV luminosity functions were derived at z ∼ 5 and z ∼ 6 taking advantage from the fact that WUDS covers a particularly interesting regime at intermediate luminosities, which allows a combined determination of M⋆ and Φ⋆ with increased accuracy. Our results on the luminosity function are consistent with a small evolution of both M⋆ and Φ⋆ between z = 5 and z = 6, irrespective of the method used to derive them, either photometric redshifts applied to blindly-selected dropout samples or the classical Lyman Break Galaxy color-preselected samples. Our results lend support to higher Φ⋆ determinations at z = 6 than usually reported. The selection and combined analysis of different galaxy samples at z ≥ 7 will be presented in a forthcoming paper, as well as the evolution of the UV luminosity function between z ∼ 4.5 and 9. WUDS is intended to provide a robust database in the near-IR for the selection of targets for detailed spectroscopic studies, in particular for the EMIR/GTC GOYA Survey.
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