arXiv subjects

L. Guzzo

Publications and source records attributed to L. Guzzo.

At least 199 records · Page 11Linked to original sources

arXiv2009

The nonlinear biasing of the 10k zCOSMOS galaxies up to z~1

We use the overdensity field reconstructed in the volume of the COSMOS area to study the nonlinear biasing of the zCOSMOS galaxies. The galaxy overdensity field is reconstructed using the current sample of ~8500 accurate zCOSMOS redshifts at I(AB)<22.5 out to z~1 on scales R from 8 to 12 Mpc/h. By comparing the probability distribution function (PDF) of galaxy density contrast delta_g to the lognormal approximation of the PDF of the mass density contrast delta, we obtain the mean biasing function b(delta,z,R) between the galaxy and matter overdensity field and its second moments b(hat) and b(tilde) up to z~1. Over the redshift interval 0.4 = b(delta,z,R) delta is of the following characteristic shape. The function vanishes in the most underdense regions and then sharply rises in a nonlinear way towards the mean densities. is almost a linear tracer of the matter in the overdense regions, up to the most overdense regions in which it is nonlinear again and the local effective slope of vs. delta is smaller than unity. The function is evolving only slightly over the redshift interval 0.4<z<1. The linear biasing parameter increases from b(hat)=1.24+/-0.11 at z=0.4 to b(hat)=1.64+/-0.15 at z=1 for the M_B<-20-z sample of galaxies. b(hat) does not show any dependence on the smoothing scale from 8 to 12 Mpc/h, but increases with luminosity. The measured nonlinearity parameter b(tilde)/b(hat) is of the order of a few percent (but it can be consistent with 0) and it does not change with redshift, the smoothing scale or the luminosity. By matching the linear bias of galaxies to the halo bias, we infer that the M_B<-20-z galaxies reside in dark matter haloes with a characteristic mass of about 3-6 x 10^12 Msol, depending on the halo bias fit.

astro-ph.CO↗

arXiv2009

The zCOSMOS survey: the role of the environment in the evolution of the luminosity function of different galaxy types

(Abridged) We studied the evolution in the B band luminosity function to z~1 in the zCOSMOS 10k sample, for which both accurate galaxy classifications and a detailed description of the local density field are available. The global LF exhibits a brightening of ~0.7 mag in M* from z~0.2 to z~0.9. At low z, late types dominate at faint magnitudes, while the bright end is populated mainly by early types. At higher z, late-type galaxies evolve significantly and, at z~1, the contribution from the various types to the bright end of the LF is comparable. The evolution for early types is in both luminosity and normalization. A similar behaviour is exhibited by late types, but with an opposite trend for the normalization. Studying the role of the environment, we find that the global LF of galaxies in overdense regions has always a brighter M* and a flatter slope. In low density environments, the main contribution to the LF is from blue galaxies, while for high density environments there is an important contribution from red galaxies to the bright end. The differences between the global LF in the two environments are not due to only a difference in the relative numbers of red and blue galaxies, but also to their relative luminosity distributions: the value of M* for both types in underdense regions is always fainter than in overdense environments. The "specular" evolution of late- and early-type galaxies is consistent with a scenario where a part of blue galaxies is transformed in red galaxies with increasing cosmic time, without significant changes in the fraction of intermediate-type galaxies. The bulk of this tranformation in overdense regions probably happened before z~1, while it is still ongoing at lower z in underdense environments.

astro-ph.CO↗

arXiv2009

The 10k zCOSMOS: morphological transformation of galaxies in the group environment since z~1

We study the evolution of galaxies inside and outside of the group environment since z=1 using a large well defined set of groups and galaxies from the zCOSMOS-bright redshift survey in the COSMOS field. The fraction of galaxies with early-type morphologies increases monotonically with M_B luminosity and stellar mass and with cosmic epoch. It is higher in the groups than elsewhere, especially at later epochs. The emerging environmental effect is superposed on a strong global mass-driven evolution, and at z~0.5 and log(M*/Msol)~10.2, the "effect" of group environment is equivalent to (only) about 0.2 dex in stellar mass or 2 Gyr in time. The stellar mass function of galaxies in groups is enriched in massive galaxies. We directly determine the transformation rates from late to early morphologies, and for transformations involving colour and star formation indicators. The transformation rates are systematically about twice as high in the groups as outside, or up to 3-4 times higher correcting for infall and the appearance of new groups. The rates reach values, for masses around the crossing mass 10^10.5 Msol, as high as (0.3-0.7)/Gyr in the groups, implying transformation timescales of 1.4-3 Gyr, compared with less than 0.2/Gyr, i.e. timescales >5 Gyr, outside of groups. All three transformation rates decrease at higher stellar masses, and must decrease also at the lower masses below 10^10 Msol which we cannot well probe. The rates involving colour and star formation are consistently higher than those for morphology, by a factor of about 50%. Our conclusion is that the transformations which drive the evolution of the overall galaxy population since z~1 must occur at a rate 2-4 times higher in groups than outside of them.

astro-ph.CO↗

arXiv2009

The zCOSMOS Redshift Survey: How group environment alters global downsizing trends

We took advantage of the wealth of information provided by the first ~10000 galaxies of the zCOSMOS-bright survey and its group catalogue to study the complex interplay between group environment and galaxy properties. The classical indicator F_blue (fraction of blue galaxies) proved to be a simple but powerful diagnostic tool. We studied its variation for different luminosity and mass selected galaxy samples. Using rest-frame B-band selected samples, the groups galaxy population exhibits significant blueing as redshift increases, but maintains a lower F_blue with respect both to the global and the isolated galaxy population. However moving to mass selected samples it becomes apparent that such differences are largely due to the biased view imposed by the B-band luminosity selection, being driven by the population of lower mass, bright blue galaxies for which we miss the redder, equally low mass, counterparts. By focusing the analysis on narrow mass bins such that mass segregation becomes negligible we find that only for the lowest mass bin explored (logMass <= 10.6) does a significant residual difference in color remain as a function of environment, while this difference becomes negligible toward higher masses. Our results indicate that red galaxies of logMass >= 10.8 are already in place at z ~ 1 and do not exhibit any strong environmental dependence, possibly originating from so-called 'nature'/internal mechanisms. In contrast, for lower galaxy masses and redshifts lower than z ~ 1, we observe the emergence in groups of a population of 'nurture' red galaxies: slightly deviating from the trend of the downsizing scenario followed by the global galaxy population, and more so with cosmic time. These galaxies exhibit signatures of group-related secular physical mechanisms directly influencing galaxy evolution.

astro-ph.CO↗

arXiv2009

The REFLEX galaxy cluster survey. VIII. Spectroscopic observations and optical atlas

We present the final data from the spectroscopic survey of the ROSAT-ESO Flux-Limited X-ray (REFLEX) catalog of galaxy clusters. The REFLEX survey covers 4.24 steradians (34% of the entire sky) below a declination of 2.5 deg and at high Galactic latitude (|b| > 20 deg). The REFLEX catalog includes 447 entries with a median redshift of 0.08 and is better than 90% complete to a limiting flux fx = 3x10^{-12} erg s^{-1} cm^{-2} (0.1 to 2.4 keV), representing the largest statistically homogeneous sample of clusters drawn from the ROSAT All-Sky Survey (RASS) to date. Here we describe the details of the spectroscopic observations carried out at the ESO 1.5 m, 2.2 m, and 3.6 m telescopes, as well as the data reduction and redshift measurement techniques. The spectra typically cover the wavelength range 3600-7500 A at a FWHM resolution of ~14 A, and the measured redshifts have a total rms error of ~100 km s^{-1}. In total we present 1406 new galaxy redshifts in 192 clusters, most of which previously did not have any redshift measured. Finally, the luminosity/redshift distributions of the cluster sample and a comparison to the no-evolution expectations from the cluster X-ray luminosity function are presented.

astro-ph.CO↗

arXiv2009

Stellar and total baryon mass fractions in groups and clusters since redshift 1

We investigate if the discrepancy between estimates of the total baryon mass fraction obtained from observations of the cosmic microwave background (CMB) and of galaxy groups/clusters persists when a large sample of groups is considered. To this purpose, 91 candidate X-ray groups/poor clusters at redshift 0.1 < z < 1 are selected from the COSMOS 2 deg^2 survey, based only on their X-ray luminosity and extent. This sample is complemented by 27 nearby clusters with a robust, analogous determination of the total and stellar mass inside R_500. The total sample of 118 groups and clusters with z < 1 spans a range in M_500 of ~10^13--10^15 M_sun. We find that the stellar mass fraction associated with galaxies at R_500 decreases with increasing total mass as (M_500)^-0.37 \pm 0.04, independent of redshift. Estimating the total gas mass fraction from a recently derived, high quality scaling relation, the total baryon mass fraction (f_500^stars+gas=f_500^stars+f_500^gas) is found to increase by ~ 25% when M_500 increases from =5 X 10^13 M_sun to = 7 X 10^14 M_sun. After consideration of a plausible contribution due to intra--cluster light (11--22% of the total stellar mass), and gas depletion through the hierarchical assembly process (10% of the gas mass), the estimated values of the total baryon mass fraction are still lower than the latest CMB measure of the same quantity (WMAP5), at a significance level of 3.3σfor groups of =5 X 10^13~M_sun. The discrepancy decreases towards higher total masses, such that it is 1σat = 7 X 10^14~M_sun. We discuss this result in terms of non--gravitational processes such as feedback and filamentary heating.

astro-ph.CO↗

arXiv2009

The Dependence of Star Formation Activity on Stellar Mass Surface Density and Sersic Index in zCOSMOS Galaxies at 0.5<z<0.9 Compared with SDSS Galaxies at 0.04<z<0.08

One of the key unanswered questions in the study of galaxy evolution is what physical processes inside galaxies drive the changes in the SFRs in individual galaxies that, taken together, produce the large decline in the global star-formation rate density (SFRD) to redshifts since z~2. Many studies of the SFR at intermediate redshifts have been made as a function of the integrated stellar mass of galaxies but these did not use information on the internal structural properties of the galaxies. In this paper we present a comparative study of the dependence of SFRs on the average surface mass densities (SigmaM) of galaxies of different morphological types up to z~1 using the zCOSMOS and SDSS surveys. The main findings about the evolution of these relatively massive galaxies are: 1) There is evidence that, for both SDSS ans zCOSMOS galaxies, the mean specific SFR within a given population (either disk-dominated or bulge-dominated) is independent of SigmaM; 2) The observed SSFR - SigmaM step-function relation is due, at all investigated redshifts, to the changing mix of disk-dominated and bulge-dominated galaxies as surface density increases and the strong difference in the average SSFR between disks and bulges. We also find a modest differential evolution in the size-mass relations of disk and spheroid galaxies; 3) The shape of the median SSFR - SigmaM relation is similar, but with median SSFR values that are about 5-6 times higher in zCOSMOS galaxies than for SDSS, across the whole range of SigmaM, and in both spheroid and disk galaxies. This increase matches that of the global SFRD of the Universe as a whole, emphasizing that galaxies of all types are contributing, proportionally, to the global increase in SFRD in the Universe back to these redshifts (abridged).

astro-ph.GA↗

arXiv2009

The zCOSMOS Redshift Survey: the role of environment and stellar mass in shaping the rise of the morphology-density relation from z~1

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. 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 10000 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. 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 10000 galaxies down to I_AB=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. ABRIDGED

astro-ph.CO↗

arXiv2009

The zCOSMOS Survey. The dependence of clustering on luminosity and stellar mass at z=0.2-1

We study the dependence of galaxy clustering on luminosity and stellar mass at redshifts z ~ [0.2-1] using the first zCOSMOS 10K sample. We measure the redshift-space correlation functions xi(rp,pi) and its projection wp(rp) for sub-samples covering different luminosity, mass and redshift ranges. We quantify in detail the observational selection biases and we check our covariance and error estimate techniques using ensembles of semi-analytic mock catalogues. We finally compare our measurements to the cosmological model predictions from the mock surveys. At odds with other measurements, we find a weak dependence of galaxy clustering on luminosity in all redshift bins explored. A mild dependence on stellar mass is instead observed. At z~0.7, wp(rp) shows strong excess power on large scales. We interpret this as produced by large-scale structure dominating the survey volume and extending preferentially in direction perpendicular to the line-of-sight. We do not see any significant evolution with redshift of the amplitude of clustering for bright and/or massive galaxies. The clustering measured in the zCOSMOS data at 0.5 =10 is only marginally consistent with predictions from the mock surveys. On scales larger than ~2 h^-1 Mpc, the observed clustering amplitude is compatible only with ~1% of the mocks. Thus, if the power spectrum of matter is LCDM with standard normalization and the bias has no unnatural scale-dependence, this result indicates that COSMOS has picked up a particularly rare, ~2-3 sigma positive fluctuation in a volume of ~10^6 h^-1 Mpc^3. These findings underline the need for larger surveys of the z~1 Universe to appropriately characterize the level of structure at this epoch.

astro-ph.CO↗

arXiv2009

The density field of the 10k zCOSMOS galaxies

We use the current sample of ~10,000 zCOSMOS spectra of sources selected with I(AB) < 22.5 to define the density field out to z~1, with much greater resolution in the radial dimension than has been possible with either photometric redshifts or weak lensing. We apply new algorithms that we have developed (ZADE) to incorporate objects not yet observed spectroscopically by modifying their photometric redshift probability distributions using the spectroscopic redshifts of nearby galaxies. This strategy allows us to probe a broader range of galaxy environments and reduce the Poisson noise in the density field. The reconstructed overdensity field of the 10k zCOSMOS galaxies consists of cluster-like patterns surrounded by void-like regions, extending up to z~1. Some of these structures are very large, spanning the ~50 Mpc/h transverse direction of the COSMOS field and extending up to Delta z~0.05 in redshift. We present the three dimensional overdensity maps and compare the reconstructed overdensity field to the independently identified virialised groups of galaxies and clusters detected in the visible and in X-rays. The distribution of the overdense structures is in general well traced by these virialised structures. A comparison of the large scale structures in the zCOSMOS data and in the mock catalogues reveals an excellent agreement between the fractions of the volume enclosed in structures of all sizes above a given overdensity between the data and the mocks in 0.2<z<1.

astro-ph.CO↗

arXiv2009

The Vimos VLT Deep Survey: Stellar mass segregation and large-scale galaxy environment in the redshift range 0.2<z<1.4

Hierarchical models of galaxy formation predict that the properties of a dark matter halo depend on the large-scale environment surrounding the halo. As a result of this correlation, we expect massive haloes to be present in larger number in overdense regions than in underdense ones. Given that a correlation exists between a galaxy stellar mass and the hosting dark matter halo mass, the segregation in dark matter halo mass should then result in a segregation in the distribution of stellar mass in the galaxy population. In this work we study the distribution of galaxy stellar mass and rest-frame optical color as a function of the large-scale galaxy distribution using the VLT VIMOS Deep Survey sample, in order to verify the presence of segregation in the properties of the galaxy population. We use the VVDS redshift measurements and multi-band photometric data to derive estimates of the stellar mass, rest-frame optical color, and of the large-scale galaxy density, on a scale of approximately 8 Mpc, for a sample of 5619 galaxies in the redshift range 0.2 0.7. However, when we consider only galaxies in narrow bins of stellar mass, in order to exclude the effects of the stellar mass segregation on the galaxy properties, we do not observe any more any significant color segregation.

astro-ph.CO↗

arXiv2009

The VIMOS VLT Deep Survey :Evolution of the major merger rate since z~1 from spectroscopicaly confirmed galaxy pairs

From the VIMOS VLT Deep Survey we use a sample of 6447 galaxies with I_{AB} < 24 to identify 251 pairs of galaxies, each member with a secure spectroscopic redshift, which are close in both projected separation and in velocity. We find that at z ~ 0.9, 10.9 +/- 3.2 % of galaxies with M_B(z) < -18-Qz are in pairs with separations dr < 20 kpc/h, dv < 500 km/s, and with dM_B < 1.5, significantly larger than 3.76 +/- 1.71 % at z ~ 0.5; we find that the pair fraction evolves as (1+z)^m with m = 2.49 +/- 0.56. For brighter galaxies with M_B(z=0) < -18.77, the pair fraction is higher and its evolution with redshift is somewhat flatter with m=1.88 \pm 0.40, a property also observed for galaxies with increasing stellar masses. Early type, dry mergers, pairs increase their relative fraction from 3 % at z ~ 0.9 to 12 % at z ~ 0.5. We find that the merger rate evolves as N_{mg}=(9.05 +/- 3.76) * 10^{-4}) * (1+z)^{2.43 +/- 0.76}. We find that the merger rate of galaxies with M_B(z) < -18-Qz has significantly evolved since z ~ 1. The merger rate is increasing more rapidly with redshift for galaxies with decreasing luminosities, indicating that the flat evolution found for bright samples is not universal. The merger rate is also strongly dependent on the spectral type of galaxies involved, late type mergers being more frequent in the past, while early type mergers are more frequent today, contributing to the rise in the local density of early type galaxies. About 20 % of the stellar mass in present day galaxies with log(M/M_{sun}) > 9.5 has been accreted through major merging events since z ~ 1, indicating that major mergers have contributed significantly to the growth in stellar mass density of bright galaxies over the last half of the life of the Universe.

astro-ph↗

arXiv2009

The XMM-Newton wide-field survey in the COSMOS field. The point-like X-ray source catalogue

The COSMOS survey is a multiwavelength survey aimed to study the evolution of galaxies, AGN and the large scale structure. The XMM-COSMOS is a deep X-ray survey over the full 2 deg2 of the COSMOS area. It consists of 55 XMM-Newton pointings for a total exposure of ~1.5 Ms with an average vignetting corrected depth of 40 ks across the field of view and a sky coverage of 2.13 deg2. We present the catalogue of point-like X-ray sources detected with the EPIC CCD cameras, the logN-logS relations and the X-ray colour-colour diagrams. The analysis was performed in the 0.5-2 keV, 2-10 keV and 5-10 keV energy bands. The completeness of the catalogue as well as logN-logS have been calibrated using Monte Carlo simulations. The catalogs contains a total of 1887 unique sources detected in at least one band. The survey, that shows unprecedented homogeneity, has a flux limit of ~1.7x10-15 erg cm-2 s-1, ~9.3x10-15 erg cm-2 s-1 and ~1.3x10-14 erg cm-2 s-1 over 90% of the area (1.92 deg2) in the 0.5-2 keV, 2-10 keV and 5-10 keV energy band, respectively. Thanks to the rather homogeneous exposure over a large area, the derived logN-logS relations are very well determined over the flux range sampled by XMM-COSMOS. These relations have been compared with XRB synthesis models, which reproduce the observations with an agreement of ~10% in the 5-10 keV and 2-10 keV band, while in the 0.5-2 keV band the agreement is of the order of ~20%. The hard X-ray colors confirmed that the majority of the extragalactic sources, in a bright subsample, are actually Type I or Type II AGN. About 20% of the sources have X-ray luminosity typical of AGN (L_X >1042 erg/s) although they do not show any clear signature of nuclear activity in the optical spectrum.

astro-ph.HE↗

arXiv2008

The spatial clustering of X-ray selected AGN in the XMM-COSMOS field

We study the spatial clustering of 538 X-ray selected AGN in the 2 deg^2 XMM-COSMOS field that are spectroscopically identified to I_{AB}<23 and span the redshift range z=0.2-3.0. The median redshift and luminosity of the sample are z = 0.98 and L_{0.5-10}=6.3 x 10^{43} erg/s, respectively. A strong clustering signal is detected at ~18sigma level, which is the most significant measurement obtained to date for clustering of X-ray selected AGN. By fitting the projected correlation function w(r_p) with a power law on scales of r_p=0.3-40 Mpc/h, we derive a best fit comoving correlation length of r_0 = 8.6 +- 0.5 Mpc/h and slope of gamma=1.88 +- 0.07 (Poissonian errors; bootstrap errors are about a factor of 2 larger). An excess signal is observed in the range r_p~5-15 Mpc/h, which is due to a large scale structure at z ~ 0.36 containing about 40 AGN. When removing the z ~ 0.36 structure, or computing w(r_p) in a narrower range around the peak of the redshift distribution (e.g. z=0.4-1.6), the correlation length decreases to r_0 ~ 5-6 Mpc/h, which is consistent with that observed for bright optical QSOs at the same redshift. We investigate the clustering properties of obscured and unobscured AGN separately. Within the statistical uncertainties, we do not find evidence that AGN with broad optical lines (BLAGN) cluster differently from AGN without broad optical lines (non-BLAGN). The correlation length measured for XMM-COSMOS AGN at z~1 is similar to that of massive galaxies (stellar mass M_*> 3 x 10^{10} M_sun) at the same redshift. This suggests that AGN at z~1 are preferentially hosted by massive galaxies, as observed both in the local and in the distant (z~2) Universe. (shortened)

astro-ph↗

arXiv2008

Photometric redshifts for the CFHTLS T0004 Deep and Wide fields

We compute photometric redshifts based on the template-fitting method 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. Our photometric redshifts are calibrated with and compared to 16,983 high-quality spectroscopic redshifts from several surveys. We find a dispersion of 0.028 and an outlier rate of 3.5% in the Deep field at i'AB < 24 and a dispersion of 0.036 and an outlier rate of 2.8% in the Wide field at i'AB < 22.5. Beyond i'AB = 22.5 in the Wide field the number of outliers rises from 5% to 10% at i'AB<23 and i'AB<24 respectively. For the Wide sample, we find the systematic redshift bias keeps below 1% to i'AB < 22.5, whereas we find no significant bias in the Deep field. We investigated the effect of tile-to-tile photometric variations and demonstrate that the accuracy of our photometric redshifts is reduced by at most 21%. We separate stars from galaxies using both the size and colour information, reducing the contamination by stars in our catalogues from 50% to 8% at i'AB < 22.5 in fields with the highest stellar density while keeping a complete galaxy sample. Our CFHTLS T0004 photometric redshifts are distributed to the community. Our release include 592,891 (i'AB < 22.5) and 244,701 (i'AB < 24) reliable galaxy photometric redshifts in the Wide and Deep fields, respectively.

astro-ph↗

arXiv2008

Testing gravity on large scales. The skewness of the galaxy distribution at z~1

We study the evolution of the low-order moments of the galaxy overdensity distribution over the redshift interval 0.7<z<1.5. We find that the variance and the normalized skewness evolve over this redshift interval in a way that is remarkably consistent with predictions of first- and second-order perturbation theory. This finding confirms the standard gravitational instability paradigm over nearly 9 Gyrs of cosmic time and demonstrates the importance of accounting for the non-linear component of galaxy biasing to avoid disagreement between theory and observations.

astro-ph↗

arXiv2008

X-ray properties in massive galaxy clusters: XMM-Newton observations of the REFLEX-DXL sample

We selected an unbiased, flux-limited and almost volume-complete sample of 13 distant, X-ray luminous (DXL, $z\sim 0.3$) clusters and one supplementary cluster at $z=0.2578$ from the REFLEX Survey (the REFLEX-DXL sample). We performed a detailed study to explore their X-ray properties using XMM-Newton observations. Based on the precise radial distributions of the gas density and temperature, we obtained robust cluster masses and gas mass fractions. The average gas mass fraction of the REFLEX-DXL sample at $r_{500}$, $0.116 \pm 0.007$, agrees with the previous cluster studies and the WMAP baryon fraction measurement. The scaled profiles of the surface brightness, temperature, entropy, gas mass and total mass are characterized by a self-similar behaviour at radii above 0.2--0.3 $r_{500}$. The REFLEX-DXL sample confirms the previous studies of the normalization of the scaling relations ($L$--$T$, $L$--$M$, $M$--$T$ and $M_{\rm gas}$--$T$) when the redshift evolution of the scaling relations is accounted for. We investigated the scatter of the scaling relations of the REFLEX-DXL sample. This gives the correlative scatter of (0.20,0.10) for variable of ($M$,$T$) of the $M_{500}$--$T$ relation, for example.

astro-ph↗

arXiv2008

Physical properties of galaxies and their evolution in the VIMOS VLT Deep Survey. I. The evolution of the mass-metallicity relation up to z~0.9

We derive the mass-metallicity relation of star-forming galaxies up to $z\sim0.9$, using data from the VIMOS VLT Deep Survey. Automatic measurement of emission-line fluxes and equivalent widths have been performed on the full spectroscopic sample. This sample is divided into two sub-samples depending on the apparent magnitude selection: wide ($I_{\mathrm{AB}}<22.5$) and deep $I_{\mathrm{AB}}<24$). These two samples span two different ranges of stellar masses. Emission-line galaxies have been separated into star-forming galaxies and active galactic nuclei using emission line ratios. For the star-forming galaxies the emission line ratios have also been used to estimate gas-phase oxygen abundance, using empirical calibrations renormalized in order to give consistent results at low and high redshifts. The stellar masses have been estimated by fitting the whole spectral energy distributions with a set of stellar population synthesis models. We assume at first order that the shape of the mass-metallicity relation remains constant with redshift. Then we find a stronger metallicity evolution in the wide sample as compared to the deep sample. We thus conclude that the mass-metallicity relation is flatter at higher redshift. The observed flattening of the mass-metallicity relation at high redshift is analyzed as an evidence in favor of the open-closed model.

astro-ph↗