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arXiv · astro-ph/0602486

An X-ray bright ERO hosting a type 2 QSO

P. Severgnini·A. Caccianiga·V. Braito·R. Della Ceca·T. Maccacaro·M. Akiyama·F. J. Carrera·M. T. Ceballos·M. J. Page·P. Saracco·M. G. Watson
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Abstract

We present the XMM-Newton and the optical-VLT spectra along with the optical and the near-infrared photometric data of one of the brightest X-ray (F(2-10 keV)~1e-13 erg/s cm^2) extremely red objects (R-K>=5) discovered so far. The source, XBSJ0216-0435, belongs to the XMM-Newton Bright Serendipitous Survey and it has extreme X-ray-to-optical (~220) and X-ray-to-near-infrared (~60) flux ratios. Thanks to its brightness, the X-ray statistics are good enough for an accurate spectral analysis by which the presence of an X-ray obscured (NH>1e22 cm^-2) QSO (L(2-10 keV)=4e45 erg/s) is determined. A statistically significant (~99%) excess around 2 keV in the observed-frame suggests the presence of an emission line. By assuming that this feature corresponds to the iron Kalpha line at 6.4 keV, a first estimate of the redshift of the source is derived (z_x~2). The presence of a high redshift QSO2 has been finally confirmed through dedicated VLT optical spectroscopic observations (z_o=1.985+/-0.002). This result yields to an optical validation of a new X-ray Line Emitting Object (XLEO) for which the redshift has been firstly derived from the X-ray data. XBSJ0216-0435 can be considered one of the few examples of X-ray obscured QSO2 at high redshift for which a detailed X-ray and optical spectral analysis has been possible. The spectral energy distribution from radio to X-rays is also presented. Finally from the near-infrared data the luminosity and the stellar mass of the host galaxy has been estimated finding a new example of the coexistence at high-z between massive galaxies and powerful QSOs.

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P. Severgnini, A. Caccianiga, V. Braito, R. Della Ceca, T. Maccacaro, M. Akiyama, F. J. Carrera, M. T. Ceballos, M. J. Page, P. Saracco, M. G. Watson. 2006-02-22. An X-ray bright ERO hosting a type 2 QSO. https://doi.org/10.1051/0004-6361%3A20053980

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