Astrophys. J., 799, 93 (2015/January-3)
Chandra deep observation of XDCP J0044.0-2033, a massive galaxy cluster at z > 1.5.
TOZZI P., SANTOS J.S., JEE M.J., FASSBENDER R., ROSATI P., NASTASI A., FORMAN W., SARTORIS B., BORGANI S., BOEHRINGER H., ALTIERI B., PRATT G.W., NONINO M. and JONES C.
Abstract (from CDS):
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 Rext= 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 = 6.7–0.9+1.3 keV, and a iron abundance ZFe = 0.41–0.26+0.29 ZFe☉ (error bars correspond to 1σ). We fit the background-subtracted surface brightness profile with a single β-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 Rext= 375 kpc to be MICM(r < Rext) = (1.48±0.20)x1013 M☉. Under the assumption of hydrostatic equilibrium and assuming isothermality within Rext, the total mass is M2500 = 1.23–0.27+0.46 x 1014M☉ for R2500 = 240–20+30 kpc. Extrapolating the profile at radii larger than the extraction radius Rext we find M500 = 3.2–0.6+0.9x 1014M☉ for R500 = 526–37+50 kpc. This analysis establishes the existence of virialized, massive galaxy clusters at redshift z ∼ 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 ΛCDM cosmology.
galaxies: clusters: intracluster medium - galaxies: individual: XDCP J0044.0-2033 - large-scale structure of universe - X-rays: galaxies: clusters
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