175 research outputs found
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
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
Three-dimensional Multi-probe Analysis of the Galaxy Cluster A1689
We perform a 3D multi-probe analysis of the rich galaxy cluster A1689 by
combining improved weak-lensing data from new BVRi'z' Subaru/Suprime-Cam
observations with strong-lensing, X-ray, and Sunyaev-Zel'dovich effect (SZE)
data sets. We reconstruct the projected matter distribution from a joint
weak-lensing analysis of 2D shear and azimuthally integrated magnification
constraints, the combination of which allows us to break the mass-sheet
degeneracy. The resulting mass distribution reveals elongation with axis ratio
~0.7 in projection. When assuming a spherical halo, our full weak-lensing
analysis yields a projected concentration of
(), consistent with and improved from earlier weak-lensing
work. We find excellent consistency between weak and strong lensing in the
region of overlap. In a parametric triaxial framework, we constrain the
intrinsic structure and geometry of the matter and gas distributions, by
combining weak/strong lensing and X-ray/SZE data with minimal geometric
assumptions. We show that the data favor a triaxial geometry with minor-major
axis ratio 0.39+/-0.15 and major axis closely aligned with the line of sight
(22+/-10 deg). We obtain and
, which overlaps with the tail of the predicted
distribution. The shape of the gas is rounder than the underlying matter but
quite elongated with minor-major axis ratio 0.60+/-0.14. The gas mass fraction
within 0.9Mpc is 10^{+3}_{-2}%. The thermal gas pressure contributes to ~60% of
the equilibrium pressure, indicating a significant level of non-thermal
pressure support. When compared to Planck's hydrostatic mass estimate, our
lensing measurements yield a spherical mass ratio of and with and without corrections for lensing projection
effects, respectively.Comment: Accepted by ApJ. Minor textual changes to improve clarity (e.g., 5.
HST STRONG-LENSING ANALYSIS). 26 pages, 17 figures. A version with
high-resolution figures is available at
http://www.asiaa.sinica.edu.tw/~keiichi/upfiles/Umetsu15/umetsu15.pd
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&
A Detailed Study of Photometric Redshifts for GOODS-South Galaxies
We use the deepest and the most comprehensive photometric data currently
available for GOODS-South galaxies to measure their photometric redshifts. The
photometry includes VLT/VIMOS (U-band), HST/ACS (F435W, F606W, F775W, and
F850LP bands), VLT/ISAAC (J-, H-, and Ks-bands), and four Spitzer/IRAC channels
(3.6, 4.5, 5.8, and 8.0 micron). The catalog is selected in the z-band (F850LP)
and photometry in each band is carried out using the recently completed TFIT
algorithm, which performs PSF matched photometry uniformly across different
instruments and filters, despite large variations in PSFs and pixel scales.
Photometric redshifts are derived using the GOODZ code, which is based on the
template fitting method using priors. The code also implements "training" of
the template SED set, using available spectroscopic redshifts in order to
minimize systematic differences between the templates and the SEDs of the
observed galaxies. Our final catalog covers an area of 153 sq. arcmin and
includes photometric redshifts for a total of 32,505 objects. The scatter
between our estimated photometric and spectroscopic redshifts is sigma=0.040
with 3.7% outliers to the full z-band depth of our catalog, decreasing to
sigma=0.039 and 2.1% outliers at a magnitude limit m(z)<24.5. This is
consistent with the best results previously published for GOODS-S galaxies,
however, the present catalog is the deepest yet available and provides
photometric redshifts for significantly more objects to deeper flux limits and
higher redshifts than earlier works. Furthermore, we show that the photometric
redshifts estimated here for galaxies selected as dropouts are consistent with
those expected based on the Lyman break technique.Comment: 62 pages, 21 figures. Minor changes to match version to be published
in Ap
Frontier Fields: Subaru Weak-Lensing Analysis of the Merging Galaxy Cluster A2744
We present a weak-lensing analysis of the merging Frontier Fields (FF) cluster Abell 2744 using new Subaru/Suprime-Cam imaging. The wide-field lensing mass distribution reveals this cluster is comprised of four distinct substructures. Simultaneously modeling the two-dimensional reduced shear field using a combination of a Navarro-Frenk-White (NFW) model for the main core and truncated NFW models for the subhalos, we determine their masses and locations. The total mass of the system is constrained as {M}200{{c}}=(2.06+/- 0.42)× {10}15 {M}⊙ . The most massive clump is the southern component with {M}200{{c}}=(7.7+/- 3.4)× {10}14 {M}⊙ , followed by the western substructure ({M}200{{c}}=(4.5+/- 2.0)× {10}14 {M}⊙ ) and two smaller substructures to the northeast ({M}200{{c}}=(2.8+/- 1.6)× {10}14 {M}⊙ ) and northwest ({M}200{{c}}=(1.9+/- 1.2)× {10}14 {M}⊙ ). The presence of the four substructures supports the picture of multiple mergers. Using a composite of hydrodynamical binary simulations we explain this complicated system without the need for a “slingshot” effect to produce the northwest X-ray interloper, as previously proposed. The locations of the substructures appear to be offset from both the gas ({87}-28+34 arcsec, 90% CL) and the galaxies ({72}-53+34 arcsec, 90% CL) in the case of the northwestern and western subhalos. To confirm or refute these findings, high resolution space-based observations extending beyond the current FF limited coverage to the west and northwestern area are essential. Based in part on data collected at the Subaru Telescope, which is operated by the National Astronomical Society of Japan
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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