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|Title:||Chandra Deep Observation of XDCP J0044.0-2033, a Massive Galaxy Cluster at z > 1.5||Authors:||TOZZI, Paolo
Santos, J. S.
Jee, M. J.
Pratt, G. W.
|Issue Date:||2015||Journal:||THE ASTROPHYSICAL JOURNAL||Number:||799||Issue:||1||First Page:||93||Abstract:||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 <SUB>ext</SUB> = 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<SUP>+1.3</SUP><SUB>-0.9</SUB> keV, and a iron abundance Z<SUB>Fe</SUB> = 0.41<SUB>-0.26</SUB><SUP>+0.29</SUP>Z<SUB>Fe_☉ </SUB> (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 R <SUB>ext</SUB> = 375 kpc to be M <SUB>ICM</SUB>(r < R <SUB>ext</SUB>) = (1.48 ± 0.20) × 10<SUP>13</SUP> M <SUB>☉</SUB>. Under the assumption of hydrostatic equilibrium and assuming isothermality within R <SUB>ext</SUB>, the total mass is M<SUB>2500</SUB>= 1.23<SUB>-0.27</SUB><SUP>+0.46</SUP> × 10 <SUP>14</SUP> M_☉ for R<SUB>2500</SUB> = 240<SUB>-20</SUB><SUP>+30</SUP> kpc. Extrapolating the profile at radii larger than the extraction radius R <SUB>ext</SUB> we find M<SUB>500</SUB> = 3.2<SUB>-0.6</SUB><SUP>+0.9</SUP> × 10 <SUP>14</SUP> M_☉ for R<SUB>500</SUB> = 562<SUB>-37</SUB><SUP>+50</SUP> 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.||Acknowledgments:||We acknowledge financial contribution from contract PRIN INAF 2012 (“A unique data set to address the most compelling open questions about X-ray galaxy clusters”), and PRIN MIUR 2009 (“ Tracing the growth of structures in the Universe ”). H.B. acknowledges support from the DFG Transregio program “Dark Universe” and the Munich Excellence Cluster ‘Structure and Evolution of the Universe”. This work was carried out with Chandra Program 14800360 obtained in AO14. J.S.S. acknowledges funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement number 267251 Astronomy Fellowships in Italy (AstroFIt). We acknowledge the hospitality of Villa Il Gioiello (Arcetri, Florence), which is part of the agreement regarding the Colle di Galileo, where some of the results presented here were discussed. Finally, we thank the referee, Pasquale Mazzotta, for his careful and critical reading of this manuscript.||URI:||http://hdl.handle.net/20.500.12386/23356||URL:||https://iopscience.iop.org/article/10.1088/0004-637X/799/1/93||ISSN:||0004-637X||DOI:||10.1088/0004-637X/799/1/93||Bibcode ADS:||2015ApJ...799...93T||Fulltext:||open|
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