An X-ray underluminous cluster of galaxies in the 4Ms CDFS observations

New Journal of Physics, 2011

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 < ∼ 1.6 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, of which 49.4 deg 2 are part of the core survey with a quantifiable selection function and 17.7 deg 2 are classified as 'gold' coverage as starting point for upcoming cosmological applications. Distant cluster candidates were followed-up with moderately deep optical and near-infrared imaging in at least two bands to photometrically identify the cluster galaxy populations and obtain redshift estimates based on colors of simple stellar population models. We test and calibrate the most promising 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∼1.5, while the redshift evolution of the R−z color leads to increasingly large uncertainties at z > ∼ 0.9. Photometrically identified high-z systems are spectroscopically confirmed with VLT/FORS 2 with a minimum of three concordant cluster member redshifts. We present first details of two newly identified clusters, ‡ Based on observations under program IDs 079.A-0634 and 085.A-0647 collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, and observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC). § Visiting astronomer at MPE. The X-ray luminous galaxy cluster population at 0.9 < z ≤ 1.6 as revealed by the XDCP 2 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 luminositybased total mass estimates for the full sample of 22 high-z clusters, of which 17 are at z ≥ 1.0 and 7 populate the highest redshift bin at z > 1.3. The median system mass of the sample is M 200 ≃ 2 × 10 14 M ⊙ , while the probed mass range for the distant clusters spans approximately (0.7-7)×10 14 M ⊙. The majority (>70%) of the X-ray selected clusters show rather regular Xray morphologies, albeit in most cases with a discernible elongation along one axis. 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 ∆m 12 ≃ 0.3 mag. We estimate a fraction of cluster-associated NVSS 1.4 GHz radio sources of about 30%, preferentially located within 1 ′ from the X-ray center. This value suggests an increase of the fraction of very luminous cluster-associated radio sources by about a factor of 2.5-5 relative to low-z systems. The galaxy populations in z > ∼ 1.5 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. The presented XDCP high-z sample will allow first detailed studies of the cluster population during the critical cosmic epoch at lookback times of 7.3-9.5 Gyr on the aggregation and evolution of baryons in the cold and hot phases as a function of redshift and system mass.

The Astrophysical …, 2003

We present new Chandra X-ray observations of the luminous and cosmologicallysignificant X-ray cluster of galaxies, MS0451.6-0305, at z = 0.5386. Spectral imaging data for the cluster are consistent with an isothermal cluster of (10.0 − 10.6) ± 1.6 keV, with an intracluster Fe abundance of (0.32−0.40)±0.13 solar. The systematic uncertainties, arising from calibration and model uncertainties, of the temperature determination are nearly the same size as the statistical uncertainties, since the time-dependent correction for absorption on the detector is uncertain for these data. We discuss the effects of this correction on the spectral fitting. The effects of statistics and fitting assumptions of 2-D models for the X-ray surface brightness are thoroughly explored. This cluster appears to be elongated and so we quantify the effects of assuming an ellipsoidal gas distribution on the gas mass and the total gravitating mass estimates. These data are also jointly fit with previous Sunyaev-Zel'dovich observations to obtain an estimate of the cluster's distance (D A = 1219 +340 −288 ± 387 Mpc, statistical followed by systematic uncertainties) assuming spherical symmetry. If we, instead, assume a Hubble constant, -2the X-ray and S-Z data are used together to test the consistency of an ellipsoidal gas distribution and to weakly constrain the intrinsic axis ratio. The mass derived from the X-ray data is consistent with the weak lensing mass and is only marginally less than the mass determined from the optical velocities. We confirm that this cluster is very hot and massive, further supporting the conclusion of previous analyses that the universe has a low matter density and that cluster properties have not evolved much since z ∼ 0.5. Furthermore the presence of iron in this high redshift cluster at an abundance that is the same as that of low redshift clusters implies that there has been very little evolution of the cluster iron abundance since z ∼ 0.5. We discuss the possible detection of a faint, soft, extended component that may be the by-product of hierarchical structure formation.

Astrophysical Journal, 1998

The strong negative evolution observed in previous X-ray selected surveys of clusters of galaxies is evidence in favour of hierarchical models of the growth of structure in the Universe. A large recent survey has, however, contradicted the low redshift results, finding no evidence for evolution at z<0.3 ). Here we present the first results from an X-ray selected, flux and surface brightness limited deep survey for high redshift clusters and groups of galaxies based on ROSAT PSPC pointed data. The log(N)-log(S) relation of all clusters in this survey is consistent with that from most previous surveys but occupies a flux range not previously covered (>6x10 −14 erg cm −2 s −1 total flux in the 0.5-2 keV band). At high redshifts (z>0.3) the cluster luminosities are in the range 4x10 43 h −2 50 erg s −1 to 2x10 44 h −2 50 erg s −1 , the luminosities of poor clusters. The number of high redshift, low luminosity clusters is consistent with no evolution of the X-ray luminosity function between redshifts of z≈0.4 and z=0, and places a limit of a factor of <1.7 (at 90% confidence) on the amplitude of any pure negative density evolution of clusters of these luminosities, in contrast with the factor of ≈3 (corresponding to number density evolution ∝(1+z) −2.5 ) found in the EMSS survey at similar redshifts but higher luminosities. Taken together, these results support hierarchical models in which there is mild negative evolution of the most luminous clusters at high redshift but little or no evolution of the less luminous but more common, optically poor clusters. Models involving preheating of the X-ray gas at an early epoch fit the observations, at least for Ω 0 =1.

The Astronomical Journal, 2005

We present a photometric and spectroscopic study of stellar populations in the X-ray-luminous cluster of galaxies RXJ0142.0+2131 at z = 0.280. This paper analyses the results of high signal-to-noise spectroscopy, as well as g ′ -, r ′ -, and i ′ -band imaging, using the Gemini Multi-Object Spectrograph on Gemini North. Of 43 spectroscopic targets, we find 30 cluster members over a range in color. Central velocity dispersions and absorption-line strengths for lines in the range 3700Å λ rest 5800Å are derived for cluster members, and are compared with a low-redshift sample of cluster galaxies, and single stellar population (SSP) models. We use a combination of these indicators to estimate luminosity-weighted mean ages, metallicities ([M/H]), and α-element abundance ratios ([α/Fe]).

Astrophysical Journal, 2000

The Wide Angle ROSAT Pointed Survey team reviews the properties and history of the discovery of Cl J0152.7[1357, an X-ray luminous, rich cluster of galaxies at a redshift of z \ 0.833. At L X \ 8 ] 1044 ergs s~1 (0.5È2.0 keV) Cl J0152.7[1357 is the most X-ray luminous cluster known at redshifts h 50 2 z [ 0.55. The high X-ray luminosity of the system suggests that massive clusters may begin to form at redshifts considerably greater than unity. This scenario is supported by the high degree of optical and X-ray substructure in Cl J0152.7[1357, which is similarly complex as that of other X-rayÈselected clusters at comparable redshift and consistent with the hypothesized picture of cluster formation by mass infall along large-scale Ðlaments.