406 research outputs found
CLASH-VLT: Is there a dependence in metallicity evolution on galaxy structures?
We investigate the environmental dependence of the mass-metallicty (MZ)
relation and it's connection to galaxy stellar structures and morphologies. In
our studies, we analyze galaxies in massive clusters at z~0.4 from the CLASH
(HST) and CLASH-VLT surveys and measure their gas metallicities, star-formation
rates, stellar structures and morphologies. We establish the MZ relation for 90
cluster and 40 field galaxies finding a shift of ~-0.3 dex in comparison to the
local trends seen in SDSS for the majority of galaxies with logM<10.5. We do
not find significant differences of the distribution of 4 distinct
morphological types that we introduce by our classification scheme (smooth,
disc-like, peculiar, compact). Some variations between cluster and field
galaxies in the MZ relation are visible at the high mass end. However, obvious
trends for cluster specific interactions (enhancements or quenching of SFRs)
are missing. In particular, galaxies with peculiar stellar structures that hold
signs for galaxy interactions, are distributed in a similar way as disc-like
galaxies - in SFRs, masses and O/H abundances. We further show that our sample
falls around an extrapolation of the star-forming main sequence (the SFR-M*
relation) at this redshift, indicating that emission-line selected samples do
not have preferentially high star-formation rates (SFRs). However, we find that
half of the high mass cluster members (M*>10^10Msun) lie below the main
sequence which corresponds to the higher mass objects that reach solar
abundances in the MZ diagram.Comment: Proceedings of IAU Symposium 309, Vienna, ed. B.L. Ziegler, F.
Combes, H. Dannerbauer, M. Verdug
On the Fe abundance peak formation in cool-core clusters of galaxies: hints from cluster WARPJ1415.1+3612 at z=1.03
We present a detailed study of the iron content of the core of the
high-redshift cluster WARPJ1415.1+3612 (z=1.03). By comparing the central Fe
mass excess observed in this system, M_Fe^exc = (1.67 +/- 0.40) x 10^9 M_sun,
with those measured in local cool-core systems, we infer that the bulk of the
mass excess was already in place at z=1, when the age of the Universe was about
half of what it is today. Our measures point to an early and intense period of
star formation most likely associated with the formation of the BCG. Indeed, in
the case of the power-law delay time distribution with slope -1, which
reproduces the data of WARPJ1415.1+3612 best, half of the supernovae explode
within 0.4 Gyr of the formation of the BCG. Finally, while for local cool-core
clusters the Fe distribution is broader than the near infrared light
distribution of the BCG, in WARPJ1415.1+3612 the two distributions are
consistent, indicating that the process responsible for broadening the Fe
distribution in local systems has not yet started in this distant cluster.Comment: 10 pages, accepted for publication in A&A, minor language corrections
added in v
Discovery of a massive X-ray luminous galaxy cluster at z=1.579
We report on the discovery of a very distant galaxy cluster serendipitously
detected in the archive of the XMM-Newton mission, within the scope of the
XMM-Newton Distant Cluster Project (XDCP). XMMUJ0044.0-2033 was detected at a
high significance level (5sigma) as a compact, but significantly extended
source in the X-ray data, with a soft-band flux f(r<40")=(1.5+-0.3)x10^(-14)
erg/s/cm2. Optical/NIR follow-up observations confirmed the presence of an
overdensity of red galaxies matching the X-ray emission. The cluster was
spectroscopically confirmed to be at z=1.579 using ground-based VLT/FORS2
spectroscopy. The analysis of the I-H colour-magnitude diagram shows a sequence
of red galaxies with a colour range [3.7 < I-H < 4.6] within 1' from the
cluster X-ray emission peak. However, the three spectroscopic members (all with
complex morphology) have significantly bluer colours relative to the observed
red-sequence. In addition, two of the three cluster members have [OII]
emission, indicative of on-going star formation. Using the spectroscopic
redshift we estimated the X-ray bolometric luminosity, Lbol = 5.8x10^44 erg/s,
implying a massive galaxy cluster. This places XMMU J0044.0-2033 at the
forefront of massive distant clusters, closing the gap between lower redshift
systems and recently discovered proto- and low-mass clusters at z >1.6.Comment: letter to appear in A&
The Chandra Deep Field South: the 1 Million Second
We present the main results from our 940 ksec observation of the Chandra Deep
Field South (CDFS), using the source catalog described in an accompanying paper
(Giacconi et al. 2001). We extend the measurement of source number counts to
5.5e-17 erg/cm^2/s in the soft 0.5-2 keV band and 4.5e-16 erg/cm^2/s in the
hard 2-10 keV band. The hard band LogN-LogS shows a significant flattening
(slope~=0.6) below ~1e-14 erg/cm^2/s, leaving at most 10-15% of the X-ray
background (XRB) to be resolved, the main uncertainty lying in the measurement
of the total flux of the XRB. On the other hand, the analysis in the very hard
5-10 keV band reveals a relatively steep LogN-LogS (slope ~=1.3) down to 1e-15
erg/cm^2/s. Together with the evidence of a progressive flattening of the
average X-ray spectrum near the flux limit, this indicates that there is still
a non negligible population of faint hard sources to be discovered at energies
not well probed by Chandra, which possibly contribute to the 30 keV bump in the
spectrum of the XRB. We use optical redshifts and identifications, obtained
with the VLT, for one quarter of the sample to characterize the combined
optical and X-ray properties of the CDFS sample. Different source types are
well separated in a parameter space which includes X-ray luminosity, hardness
ratio and R-K color. Type II objects, while redder on average than the field
population, have colors which are consistent with being hosted by a range of
galaxy types. Type II AGN are mostly found at z<~1, in contrast with
predictions based on AGN population synthesis models, thus suggesting a
revision of their evolutionary parameters.Comment: Accepted by The Astrophysical Journal, 24 pages, 8 figures, 1 color
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