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The two brightest peaks in the red galaxy population mark the X-ray selected clusters and are well-centered on the di ff use X-ray emission. On the other hand, the optically selected system
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X-ray luminous clusters of galaxies at z~1 are emerging as major cosmological probes and are fundamental tools to study the cosmic large-scale structure and environmental effects of galaxy evolution at large look-back times. We present details of the newly-discovered galaxy cluster XMMU J0104.4-0630 at z=0.947 and a probable associated system in th...
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Studies of low surface brightness (LSB) galaxies in nearby clusters have revealed a sub-population of extremely diffuse galaxies with central surface brightness $\mu_{0,g'}$ > 24 mag arcsec$^{-2}$ and effective radius between 1.5 kpc < R$_{e}$ < 10 kpc. The origin of these Ultra Diffuse Galaxies (UDGs) is still unclear, although several theories ha...
We present results on the evolution of the structural parameters of two samples of brightest cluster galaxies (BCGs) in the last 6 Gyr. The nearby sample of BCGs consists of 69 galaxies from the WINGS survey spanning a redshift range of 0.04 < z < 0.07. The intermediate-redshift (0.3 < z < 0.6) sample is formed by 20 BCGs extracted from the Hubble...
We present a study of remarkably luminous and unique dwarf galaxies at redshifts of 0.5 < z < 0.7, selected from the DEEP2 Galaxy Redshift survey by the presence of the temperature sensitive [OIII]λ4363 emission line. Measurements of this important auroral line, as well as other strong oxygen lines, allow us to estimate the integrated oxygen abunda...
We combine imaging data from the Advanced Camera for Surveys (ACS) with VLT/FORS optical spectroscopy to study the properties of star-forming galaxies in the z = 0.837 cluster Cl 0152-1357. We have morphological information for 24 star-forming cluster galaxies, which range in morphology from late-type and irregular to compact early-type galaxies. W...
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We report the discovery of a molecular wind signature from a massive intensely star-forming clump of a few 10⁹  M⊙, in the strongly gravitationally lensed submillimeter galaxy "the Emerald" (PLCK-G165.7+49.0) at z = 2.236. The Emerald is amongst the brightest high-redshift galaxies on the submillimeter sky, and was initially discovered with the Planck satellite. The system contains two magnificient structures with projected lengths of 28.5″ and 21″ formed by multiple, near-infrared arcs, falling behind a massive galaxy cluster at z = 0.35, as well as an adjacent filament that has so far escaped discovery in other wavebands. We used HST/WFC3 and CFHT optical and near-infrared imaging together with IRAM and SMA interferometry of the CO(4-3) line and 850 μm dust emission to characterize the foreground lensing mass distribution, construct a lens model with LENSTOOL, and calculate gravitational magnification factors between 20 and 50 in most of the source. The majority of the star formation takes place within two massive star-forming clumps which are marginally gravitationally bound and embedded in a 9×10¹⁰  M⊙, fragmented disk with 20% gas fraction. The stellar continuum morphology is much smoother and also well resolved perpendicular to the magnification axis. One of the clumps shows a pronounced blue wing in the CO(4-3) line profile, which we interpret as a wind signature. The mass outflow rates are high enough for us to suspect that the clump might become unbound within a few tens of Myr, unless the outflowing gas can be replenished by gas accretion from the surrounding disk. The velocity offset of -200 km s⁻¹ is above the escape velocity of the clump, but not that of the galaxy overall, suggesting that much of this material might ultimately rain back onto the galaxy and contribute to fueling subsequent star formation.
Observational constraints on the average radial distribution profile of AGN in distant galaxy clusters can provide important clues on the triggering mechanisms of AGN activity in dense environments
and are essential for a completeness evaluation of cluster selection techniques in the X-ray and
mm wavebands. The aim of this work is a statistical study with XMM-Newton of the presence
and distribution of X-ray AGN in the large-scale structure environments of 22 X-ray luminous galaxy clusters in the redshift range 0.9
In this paper we study the large scale structures and their galaxy content
around the most X-ray luminous cluster known, RX J1347.5-1145 at z=0.45. We
make use of ugriz CFHT MEGACAM photometry and VIMOS VLT spectroscopy to
identify structures around the RXJ1347 on a scale of 20x20 Mpc2. We construct
maps of the galaxy distribution and the fraction of blue galaxies. We study the
photometric galaxy properties as a function of environment, traced by the
galaxy density. We identify group candidates based on galaxy overdensities and
study their galaxy content. We also use available GALEX NUV imaging to identify
strong unobscured star forming galaxies. We find that the large scale structure
around RXJ1347 extends in the NE-SW direction for at least 20 Mpc, in which
most of the group candidates are located. As other studies, we find that the
fraction of blue galaxies (Fblue) is a function of galaxy number density, but
the bulk of the trend is due to galaxies belonging to massive systems. The
fraction of the UV-bright galaxies is also function of environment, but their
relative numbers compared to the blue population seems to be constant
regardless of the environment. These UV emitters also have similar properties
at all galaxy densities, indicating that the transition between galaxy types
occurs in short time-scales. Candidate galaxy groups show a large variation in
their galaxy content and Fblue in those groups display little dependence with
galaxy density. This may indicate possible differences in their evolutionary
status or the processes that are acting in groups are different than in
clusters. The large scale structure around rich clusters are dynamic places for
galaxy evolution. In the case of RXJ1347 the transformation may start within
infalling groups to finish with the removal of the cold gas once galaxies are
accreted in massive systems. (ABRIDGED)
We present the largest sample of spectroscopically confirmed X-ray luminous
high-redshift galaxy clusters to date comprising 22 systems in the range
0.9<z<\sim1.6 as part of the XMM-Newton Distant Cluster Project (XDCP). All
systems were initially selected as extended X-ray sources over 76.1 deg^2 of
non-contiguous deep archival XMM-Newton coverage. We test and calibrate the
most promising two-band redshift estimation techniques based on the R-z and z-H
colors for efficient distant cluster identifications and find a good redshift
accuracy performance of the z-H color out to at least z\sim1.5, while the
redshift evolution of the R-z color leads to increasingly large uncertainties
at z>\sim0.9. We present first details of two newly identified clusters, XDCP
J0338.5+0029 at z=0.916 and XDCP J0027.2+1714 at z=0.959, and investigate the
Xray properties of SpARCS J003550-431224 at z=1.335, which shows evidence for
ongoing major merger activity along the line-of-sight. We provide X-ray
properties and luminosity-based total mass estimates for the full sample, which
has a median system mass of M200\simeq2\times10^14M\odot. In contrast to local
clusters, the z>0.9 systems do mostly not harbor central dominant galaxies
coincident with the X-ray centroid position, but rather exhibit significant BCG
offsets from the X-ray center with a median value of about 50 kpc in projection
and a smaller median luminosity gap to the second-ranked galaxy of \sim0.3mag.
We estimate a fraction of cluster-associated NVSS 1.4GHz radio sources of about
30%, preferentially located within 1' from the X-ray center. The galaxy
populations in z>\sim1.5 cluster environments show first evidence for drastic
changes on the high-mass end of galaxies and signs for a gradual disappearance
of a well-defined cluster red-sequence as strong star formation activity is
observed in an increasing fraction of massive galaxies down to the densest core
regions.
We present a photometric and spectroscopic study of galaxies at 0.5 $\lt$ ${z}$ $\lt$ 1 as a function of the environment based on data from the zCOSMOS survey. There is a fair amount of evidence that galaxy
properties depend on the mass of groups and clusters, in the sense that quiescent galaxies prefer more massive systems. We
base our analysis on a mass-selected environment using X-ray groups of galaxies, and define the group membership using a large
number of spectroscopic redshifts from zCOSMOS. We show that the fraction of red galaxies is higher in groups than in the
field at all redshifts probed in our study. Interestingly, the fraction of [O II] emitters on the red sequence increases at
higher redshifts in groups, while the fraction does not strongly evolve in the field. This is due to increased dusty star-formation
activities and/or increased activities of active galactic nuclei (AGNs) in high-redshift groups. We investigate these possibilities
using the 30-band photometry and X-ray data. We find that the stellar population of the red [O II] emitters in groups is old,
and there is no clear hint of dusty star-formation activities in those galaxies. The observed increase of red [O II] emitters
in groups is likely due to increased AGN activities. However, since our overall statistics are poor, any firm conclusions
need to be drawn from a larger statistical sample of ${z}$ $\sim$ 1 groups.
Identification of high redshift clusters is important for studies of
cosmology and cluster evolution. Using photometric redshifts of galaxies, we
identify 631 clusters from the Canada-France-Hawaii Telescope (CFHT) Wide
field, 202 clusters from the CHFT Deep field, 187 clusters from the Cosmic
Evolution Survey (COSMOS) and 737 clusters from the Spitzer Wide-area InfraRed
Extragalactic survey (SWIRE) field. The redshifts of these clusters are in the
range of 0.1<z<1.6. Merging these cluster samples gives 1644 clusters in the
four survey fields, of which 1088 are newly identified and more than half are
from the large SWIRE field. Among 228 clusters of z>1, 191 clusters are newly
identified, and most of them from the SWIRE field. With this large sample of
high redshift clusters, we study the color evolution of the brightest cluster
galaxies (BCGs). The colors r'-z' and r^+-m_{3.6\mu m} of the BCGs are
consistent with a stellar population synthesis model in which the BCGs are
formed at redshift z_f>2 and evolved passively. The colors g'-z' and
B-m_{3.6\mu m} of the BCGs at redshifts z>0.8 are systematically bluer than the
passive evolution model for galaxy formed at z_f~2, indicating star formation
in high redshift BCGs.
The XMM Cluster Survey (XCS) is a serendipitous search for galaxy clusters
using all publicly available data in the XMM-Newton Science Archive. Its main
aims are to measure cosmological parameters and trace the evolution of X-ray
scaling relations. In this paper we describe the data processing methodology
applied to the 5,776 XMM observations used to construct the current XCS source
catalogue. A total of 3,675 > 4-sigma cluster candidates with > 50
background-subtracted X-ray counts are extracted from a total non-overlapping
area suitable for cluster searching of 410 deg^2. Of these, 993 candidates are
detected with > 300 background-subtracted X-ray photon counts, and we
demonstrate that robust temperature measurements can be obtained down to this
count limit. We describe in detail the automated pipelines used to perform the
spectral and surface brightness fitting for these candidates, as well as to
estimate redshifts from the X-ray data alone. A total of 587 (122) X-ray
temperatures to a typical accuracy of < 40 (< 10) per cent have been measured
to date. We also present the methodology adopted for determining the selection
function of the survey, and show that the extended source detection algorithm
is robust to a range of cluster morphologies by inserting mock clusters derived
from hydrodynamical simulations into real XMM images. These tests show that the
simple isothermal beta-profiles is sufficient to capture the essential details
of the cluster population detected in the archival XMM observations. The
redshift follow-up of the XCS cluster sample is presented in a companion paper,
together with a first data release of 503 optically-confirmed clusters.
We present a comprehensive galaxy cluster study of XMMU J1230.3+1339 based on a joint analysis of X-ray data, optical imaging and spectroscopy observations, weak lensing results, and radio properties for achieving a detailed multi-component view of this newly discovered system at z=0.975. We find an optically very rich and massive system with M200$\simeq$(4.2$\pm$0.8)$\times$10^14 M$\sun$, Tx$\simeq$5.3(+0.7--0.6)keV, and Lx$\simeq$(6.5$\pm$0.7)$\times$10^44 erg/s, for which various widely used mass proxies are measured and compared. We have identified multiple cluster-related components including a central fly-through group close to core passage with associated marginally extended 1.4GHz radio emission possibly originating from the turbulent wake region of the merging event. On the cluster outskirts we see evidence for an on-axis infalling group with a second Brightest Cluster Galaxy (BCG) and indications for an additional off-axis group accretion event. We trace two galaxy filaments beyond the nominal cluster radius and provide a tentative reconstruction of the 3D-accretion geometry of the system. In terms of total mass, ICM structure, optical richness, and the presence of two dominant BCG-type galaxies, the newly confirmed cluster XMMU J1230.3+1339 is likely the progenitor of a system very similar to the local Coma cluster, differing by 7.6 Gyr of structure evolution. Comment: 26 pages, 14 color figures, accepted for publication in A&A
Aims. The aim of this work is to investigate the physical, structural and evolutionary properties of old, passive galaxies at $z > 1.4$ and to place new constraints on massive galaxy formation and evolution.Methods. We combine ultradeep optical spectroscopy from the GMASS project (Galaxy Mass Assembly ultradeep Spectroscopic Survey) with GOODS multi-band (optical to mid-infrared) photometry and HST imaging to study a sample of spectroscopically identified passive galaxies at $1.39 < z < 1.99$ selected from Spitzer Space Selescope imaging at 4.5 $\mu$m.Results. A stacked spectrum with an equivalent integration time of ~500 h was obtained and compared with libraries of synthetic stellar population spectra. The stacked spectrum is publicly released. The spectral and photometric SED properties indicate very weak or absent star formation, moderately old stellar ages of $\approx$1 Gyr (for solar metallicity) and stellar masses in the range of $10^{10-11}$ $M_{\odot}$, thus implying that the major star formation and assembly processes for these galaxies occurred at $z > 2$. No X-ray emission was found neither from individual galaxies nor from a stacking analysis of the sample. Only one galaxy shows a marginal detection at 24 $\mu$m. These galaxies have morphologies that are predominantly compact and spheroidal. However, their sizes ($R_{\rm e}$$\lesssim$1 kpc) are much smaller than those of spheroids in the present-day Universe. Their stellar mass surface densities are consequently higher by $\approx$1 dex if compared to spheroids at $z$$\approx$0 with the same mass. Their rest-frame $B$-band surface brightness scales with the effective radius, but the offset with respect to the surface brightness of the local Kormendy relation is too large to be explained by simple passive evolution. At $z\approx1$, a larger fraction of passive galaxies follows the $z$$\approx$0 size-mass relation. Superdense relics with $R_{\rm e}$$\approx$1 kpc are extremely rare at $z$$\approx$0 with respect to $z > 1$, and absent if $R_{\rm e}$ < 1 kpc. Because of the similar sizes and mass densities, we suggest that the superdense passive galaxies at 1 < $z$ < 2 are the remnants of the powerful starbursts occurring in submillimeter-selected galaxies at $z$ > 2. The results are compared with theoretical models and the main implications discussed in the framework of massive galaxy formation and evolution.
We report on the discovery of the X-ray luminous cluster XMMU
J100750.5+125818 at redshift 1.082 based on 19 spectroscopic members.
The cluster displays several strong lensing features. SED modeling of
the lensed arc features from multicolor imaging with the VLT and the LBT
reveals likely redshifts ~2.7 for the most prominent of the lensed
background galaxies. Mass estimates are derived for different radii from
the velocity dispersion of the cluster members, M200 ≃
1.8 × 1014 M_⊙, from the X-ray spectral parameters,
M500 ≃ 1.0 × 1014 M_⊙, and the
largest lensing arc, MSL ≃ 2.3 × 1013
M_⊙. The projected spatial distribution of cluster galaxies appears
to be elongated, and the brightest galaxy lies off center with respect
to the X-ray emission, indicating a not yet relaxed structure. XMMU
J100750.5+125818 offers excellent diagnostics of the inner mass
distribution of a distant cluster with strong and weak lensing, in
combination with optical and X-ray spectroscopy.
Based on observations made with ESO Telescopes at the La Silla or
Paranal Observatories under programs 78.A-0265 and 80.A-0659.Based on
observations obtained with XMM-Newton, an ESA science mission with
instruments and contributions directly funded by ESA Member States and
NASA.Appendix is only available in electronic form at http://www.aanda.org
