اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدThe VIMOS VLT Deep Survey. The Assembly History of the Stellar Mass in Galaxies: from the Young to the Old Universe
133
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We present a detailed analysis of the Galaxy Stellar Mass Function of galaxies up to z=2.5 as obtained from the VVDS. We estimate the stellar mass from broad-band photometry using 2 different assumptions on the galaxy star formation history and show that the addition of secondary bursts to a continuous star formation history produces systematically higher (up to 40%) stellar masses. At low redshift (z=0.2) we find a substantial population of low-mass galaxies (<10^9 Msun) composed by faint blue galaxies (M_I-M_K=0.3). In general the stellar mass function evolves slowly up to z=0.9 and more significantly above this redshift. Conversely, a massive tail is present up to z=2.5 and have extremely red colours (M_I-M_K=0.7-0.8). We find a decline with redshift of the overall number density of galaxies for all masses (59+-5% for M>10^8 Msun at z=1), and a mild mass-dependent average evolution (`mass-downsizing). In particular our data are consistent with mild/negligible (<30%) evolution up to z=0.7 for massive galaxies (>6x10^10 Msun). For less massive systems the no-evolution scenario is excluded. A large fraction (>=50%) of massive galaxies have been already assembled and converted most of their gas into stars at z=1, ruling out the `dry mergers as the major mechanism of their assembly history below z=1. This fraction decreases to 33% at z=2. Low-mass systems have decreased continuously in number and mass density (by a factor up to 4) from the present age to z=2, consistently with a prolonged mass assembly also at z<1.
قيم البحث
اقرأ أيضاً
We selected a mass-limited sample of 4048 objects from the VIMOS VLT Deep Survey in the redshift interval 0.5<z<1.3. We used the amplitude of the 4000 Balmer break (Dn4000) to separate the galaxy population and the EW[OII]3727 line as proxy for the s
tar formation activity. We discuss to what extent stellar mass drives galaxy evolution, showing for the first time the interplay between stellar ages and stellar masses over the past 8Gyr. Low-mass galaxies have small Dn4000 and at increasing stellar mass, the galaxy distribution moves to higher Dn4000 values as observed in the local Universe. As cosmic time goes by, we witness an increasing abundance of massive spectroscopically ET systems at the expense of the LT systems. This spectral transformation is a process started at early epochs and continuing efficiently down to the local Universe. This is confirmed by the evolution of our type-dependent stellar mass function. The underlying stellar ages of LT galaxies apparently do not show evolution, likely as a result of a continuous formation of new stars. All star formation activity indicators consistently point towards a star formation history peaked in the past for massive galaxies, with little or no residual star formation taking place in the most recent epochs. The activity and efficiency of forming stars are mechanisms that depend on stellar mass, and the mass assembly becomes progressively less efficient in massive systems as time elapses. The concepts of star formation downsizing and mass assembly downsizing describe a single scenario that has a top-down evolutionary pattern. The role of (dry) merging events seems to be only marginal at z<1.3, as our estimated efficiency in stellar mass assembly can possibly account for the progressive accumulation of passively evolving galaxies.
We have investigated the dependence of galaxy clustering on their stellar mass at z~1, using the data from the VIMOS-VLT Deep Survey (VVDS). We have measured the projected two-point correlation function of galaxies, wp(rp) for a set of stellar mass s
elected samples at an effective redshift <z>=0.85. We have control and quantify all effects on galaxy clustering due to the incompleteness of our low mass samples. We find that more massive galaxies are more clustered. When compared to similar results at z~0.1 in the SDSS, we observed no evolution of the projected correlation function for massive galaxies. These objects present a stronger linear bias at z~1 with respect to low mass galaxies. As expected, massive objects at high redshift are found in the highest pics of the dark matter density field.
[Abridged] We present a homogeneous and complete catalogue of optical groups identified in the purely flux limited (17.5<=I<=24.0) VIMOS-VLT Deep Survey (VVDS). We use mock catalogues extracted from the MILLENNIUM simulation, to correct for potential
systematics that might affect the overall distribution as well as the individual properties of the identified systems. Simulated samples allow us to forecast the number and properties of groups that can be potentially found in a survey with VVDS-like selection functions. We use them to correct for the expected incompleteness and also to asses how well galaxy redshifts trace the line-of-sight velocity dispersion of the underlying mass overdensity. In particular, we train on these mock catalogues the adopted group-finding technique (the Voronoi-Delaunay Method, VDM). The goal is to fine-tune its free parameters, recover in a robust and unbiased way the redshift and velocity dispersion distributions of groups and maximize the level of completeness (C) and purity (P) of the group catalogue. We identify 318 VVDS groups with at least 2 members within 0.2<=z<=1.0, among which 144 (/30) with at least 3 (/5) members. The sample has globally C=60% and P=50%. Nearly 45% of the groups with at least 3 members are still recovered if we run the algorithm with a parameter set which maximizes P (75%). We exploit the group sample to study the redshift evolution of the fraction f_b of blue galaxies (U-B<=1) within 0.2<=z<=1. We find that f_b is significantly lower in groups than in the whole ensemble of galaxies irrespectively of their environment. These quantities increase with redshift, with f_b in groups showing a marginally significant steeper increase. We also confirm that, at any explored redshift, f_b decreases for increasing group richness, and we extend towards fainter luminosities the magnitude range over which this result holds.
Aims: We use the VVDS-Deep first-epoch data to measure the dependence of galaxy clustering on galaxy stellar mass, at z~0.85. Methods: We measure the projected correlation function wp(rp) for sub-samples with 0.5<z<1.2 covering different mass range
s between 10^9 and 10^11 Msun. We quantify in detail the observational selection biases using 40 mock catalogues built from the Millennium run and semi-analytic models. Results: Our simulations indicate that serious incompleteness in mass is present only for log(M/Msun)<9.5. In the mass range log(M/Msun)=[9.0-9.5], the photometric selection function of the VVDS misses 2/3rd of the galaxies. The sample is virtually 100% complete above 10^10 Msun. We present the first direct evidence for a clear dependence of clustering on the galaxy stellar mass at z~0.85. The clustering length increases from r0 ~ 2.76 h^-1 Mpc for galaxies with mass M>10^9 Msun to r0 ~ 4.28 h^-1 Mpc for galaxies more massive than 10^10.5 Msun. At the same time, the slope increases from ~ 1.67 to ~ 2.28. A comparison of the observed wp(rp) to local measurements by the SDSS shows that the evolution is faster for objects less massive than ~10^10.5 Msun. This is interpreted as a higher dependence on redshift of the linear bias b_L for the more massive objects. While for the most massive galaxies b_L decreases from 1.5+/-0.2 at z~0.85 to 1.33+/-0.03 at z~0.15, the less massive population maintains a virtually constant value b_L~1.3. This result is in agreement with a scenario in which more massive galaxies formed at high redshift in the highest peaks of the density field, while less massive objects form at later epochs from the more general population of dark-matter halos.
The VVDS-Wide survey has been designed with the general aim of tracing the large-scale distribution of galaxies at z~1 on comoving scales reaching ~100Mpc/h, while providing a good control of cosmic variance over areas as large as a few square degree
s. This is achieved by measuring redshifts with VIMOS at the ESO VLT to a limiting magnitude I_AB=22.5, targeting four independent fields with size up to 4 sq.deg. each. The whole survey covers 8.6 sq.deg., here we present the general properties of the current redshift sample. This includes 32734 spectra in the four regions (19977 galaxies, 304 type I AGNs, and 9913 stars), covering a total area of 6.1 sq.deg, with a sampling rate of 22 to 24%. The redshift success rate is above 90% independently of magnitude. It is the currently largest area coverage among redshift surveys reaching z~1. We give the mean N(z) distribution averaged over 6.1 sq.deg. Comparing galaxy densities from the four fields shows that in a redshift bin Deltaz=0.1 at z~1 one still has factor-of-two variations over areas as large as ~0.25 sq.deg. This level of cosmic variance agrees with that obtained by integrating the galaxy two-point correlation function estimated from the F22 field alone, and is also in fairly good statistical agreement with that predicted by the Millennium mocks. The variance estimated over the survey fields shows explicitly how clustering results from deep surveys of even ~1 sq.deg. size should be interpreted with caution. This paper accompanies the public release of the first 18143 redshifts of the VVDS-Wide survey from the 4 sq.deg. contiguous area of the F22 field at RA=22h, publicly available at http://cencosw.oamp.fr
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
