We report the analysis of the Chandra observation of XDCP J0044.0-2033, a massive, distant (z=1.579) galaxy cluster discovered in the XDCP survey. The total exposure time of 380 ks with Chandra ACIS-S provides the deepest X-ray observation currently
achieved on a massive, high redshift cluster. Extended emission from the Intra Cluster Medium (ICM) is detected at a very high significance level (S/N~20) on a circular region with a 44 radius, corresponding to $R_{ext}=375$ kpc at the cluster redshift. We perform an X-ray spectral fit of the ICM emission modeling the spectrum with a single-temperature thermal mekal model. Our analysis provides a global temperature $kT=6.7^{+1.3}_{-0.9}$ keV, and a iron abundance $Z_{Fe} = 0.41_{-0.26}^{+0.29}Z_{Fe_odot}$ (error bars correspond to 1 $sigma$). We fit the background-subtracted surface brightness profile with a single $beta$-model out to 44, finding a rather flat profile with no hints of a cool core. We derive the deprojected electron density profile and compute the ICM mass within the extraction radius $R_{ext}=375$ kpc to be $M_{ICM}(r<R_{ext}) = (1.48 pm 0.20) times 10^{13} M_odot$. Under the assumption of hydrostatic equilibrium and assuming isothermality within $R_{ext}$, the total mass is $M_{2500}= 1.23_{-0.27}^{+0.46} times 10 ^{14} M_odot$ for $R_{2500} = 240_{-20}^{+30}$ kpc. Extrapolating the profile at radii larger than the extraction radius $R_{ext}$ we find $M_{500} = 3.2_{-0.6}^{+0.9} times 10 ^{14}M_odot$ for $R_{500} = 562_{-37}^{+50}$ kpc. This analysis establishes the existence of virialized, massive galaxy clusters at redshift $zsim 1.6$, paving the way to the investigation of the progenitors of the most massive clusters today. Given its mass and the XDCP survey volume, XDCP J0044.0-2033 does not create significant tension with the WMAP-7 $Lambda$CDM cosmology.
Star-formation in the galaxy populations of local massive clusters is reduced with respect to field galaxies, and tends to be suppressed in the core region. Indications of a reversal of the star-formation--density relation have been observed in a few
z >1.4 clusters. Using deep imaging from 100-500um from PACS and SPIRE onboard Herschel, we investigate the infrared properties of spectroscopic and photo-z cluster members, and of Halpha emitters in XMMU J2235.3-2557, one of the most massive, distant, X-ray selected clusters known. Our analysis is based mostly on fitting of the galaxies spectral energy distribution in the rest-frame 8-1000um. We measure total IR luminosity, deriving star formation rates (SFRs) ranging from 89-463 Msun/yr for 13 galaxies individually detected by Herschel, all located beyond the core region (r >250 kpc). We perform a stacking analysis of nine star-forming members not detected by PACS, yielding a detection with SFR=48 Msun/yr. Using a color criterion based on a star-forming galaxy SED at the cluster redshift we select 41 PACS sources as candidate star-forming cluster members. We characterize a population of highly obscured SF galaxies in the outskirts of XMMU J2235.3-2557. We do not find evidence for a reversal of the SF-density relation in this massive, distant cluster.
(Abridged) We report the discovery of CXO J1415.2+3610, a distant (z~1.5) galaxy cluster serendipitously detected in a deep, high-resolution Chandra observation targeted to study the cluster WARP J1415.1+3612 at z=1.03. This is the highest-z cluster
discovered with Chandra so far. Moreover, the total exposure time of 280 ks with ACIS-S provides the deepest X-ray observation currently achieved on a cluster at z>1.5. We perform an X-ray spectral fit of the extended emission of the intracluster medium (ICM) with XSPEC, and we detect at a 99.5% confidence level the rest frame 6.7-6.9 keV Iron K_alpha line complex, from which we obtain z_X=1.46pm0.025. The analysis of the z-3.6mu m color-magnitude diagram shows a well defined sequence of red galaxies within 1 from the cluster X-ray emission peak with a color range [5 < z-3.6 mu m < 6]. The photometric redshift obtained by spectral energy distribution (SED) fitting is z_phot=1.47pm 0.25. After fixing the redshift to z=1.46, we perform the final spectral analysis and measure the average gas temperature with a 20% error, kT=5.8^{+1.2}_{-1.0} keV, and the Fe abundance Z_Fe = 1.3_{-0.5}^{+0.8}Z_odot. We fit the background subtracted surface brightness with a single beta--model out to 35 and derive the deprojected electron density profile. The ICM mass is 1.09_{-0.2}^{+0.3}times 10^{13} M_odot within 300 kpc. The total mass is M_{2500}= 8.6_{-1.7}^{+2.1} times 10 ^{13} M_odot for R_{2500}=(220pm 55) kpc. Extrapolating the profile at larger radii we find M_{500}= 2.1_{-0.5}^{+0.7} times 10 ^{14} M_odot for R_{500} = 510_{-50}^{+55}$ kpc. This analysis establishes CXOJ1415.2+3610 as one of the best characterized distant galaxy clusters based on X-ray data alone.
