ChandraandXMM-NewtonObservations of RDCS 1252.9-2927, A Massive Cluster atz=1.24

Abstract

We present deep Chandra and XMM-Newton observations of the galaxy cluster RDCS 1252.9À2927, which was selected from the ROSAT Deep Cluster Survey (RDCS) and confirmed by extensive spectroscopy with the Very Large Telescope at redshift z = 1.237. With the Chandra data, the X-ray emission from the intracluster medium is well resolved and traced out to 500 kpc, thus allowing a measurement of the physical properties of the gas with unprecedented accuracy at this redshift. We detect a clear 6.7 keV iron K line in the Chandra spectrum providing a redshift within 1% of the spectroscopic one. By augmenting our spectroscopic analysis with the XMM-Newton data (MOS detectors only), we significantly narrow down the 1 error bar to 10% for the temperature and 30% for the metallicity, with best-fit values kT ¼ 6:0 þ0:7 À0:5 keV, Z ¼ 0:36 þ0:12 À0:10 Z . On the likely hypothesis of hydrostatic equilibrium, we measure a total mass of M 500 ¼ ð1:9 AE 0:3Þ Â 10 14 h À1 70 M within R Á=500 ' 536 kpc. Overall, these observations imply that RDCS 1252.9À2927 is the most X-ray luminous and likely the most massive bona fide cluster discovered to date at z > 1. When combined with current samples of distant clusters, these data lend further support to a mild evolution of the cluster scaling relations, as well the metallicity of the intracluster gas. Inspection of the cluster mass function in the current cosmological concordance model (h, m , Ã ) = (0.7, 0.3, 0.7) and 8 = 0.7-0.8 shows that RDCS 1252.9À2927 is an M* cluster at z = 1.24, in keeping with number density expectations in the RDCS survey volume.

A new (2+1)D cluster finding algorithm based on photometric redshifts: large scale structure in the Chandra deep field south

“…Our analysis supports the evidence of a constant C-M slope up to z = 1, meaning a correspondingly constant mass-metallicity relation. We stress that most of the highest redshift clusters detected so far were selected in the X-ray band, in particular those at z = 1.24 (Blakeslee et al 2003;Rosati et al 2004) and z = 1.4 (Mullis et al 2005). However, both these clusters have a velocity dispersion of about 800 km s −1 and intracluster gas temperature kT ∼ 6 keV, typical of rich clusters (Bahcall 1988;Arnaud et al 2005).…”

“…However, both these clusters have a velocity dispersion of about 800 km s −1 and intracluster gas temperature kT ∼ 6 keV, typical of rich clusters (Bahcall 1988;Arnaud et al 2005). The X-ray luminosities of these two clusters in the 0.5-2 keV band are 1.9 × 10 44 and 3.0 × 10 44 erg s −1 h −2 70 respectively (Rosati et al 2004;Mullis et al 2005), again typical of clusters with richness class greater than 2 (Ledlow et al 2003). Rich clusters of these redshifts are just at the limit of our present (2+1)D analysis based on photometric observations.…”

Early assembly of the most massive galaxies

“…If cluster masses have grown by a factor 2 or 3 since z ≃ 1, as some authors suggest 33 In order to compare our data with simulations we use the bolometric X-ray luminosity of each system (L X ) 11,12,34,35 as this can be used to determine cluster mass from power-law scaling relations 36,37 . For J2235 we use the published X-ray luminosity 15 …”

Indications for 3 Mpc-scale large-scale structure associated with an X-ray luminous cluster of galaxies at z = 0.95

“…However, significant progress is still required to fully characterize the high redshift (z > ∼ 0.9) cluster population, which has been limited to few known and well studied test objects so far (e.g., Rosati et al 2004;Hashimoto et al 2005). Detailed studies have recently revealed large-scale structure (LSS) associated with several of the known bona fide X-ray clusters in the Lynx field at z = 1.27 (Nakata et al 2005) and for RDCS J1252.9-2927 at z = 1.24 (Tanaka et al 2007).…”