Looking for obscured QSOs in the X-ray emitting ERO population
Por:
Severgnini P., Delia Ceca R., Braito V., Saracco P., Longhetti M., Bender R., Drory N., Feulner G., Hopp U., Mannucci F., Maraston C.
Publicada:
1 ene 2005
Resumen:
We present XMM-Newton data centered on one of the MUNICS Near Infrared Cluster Survey fields (S2F1) and we discuss the X-ray properties of the 6 X-ray emitting EROs found. For one of them we have already obtained the redshift using near-infrared spectroscopic data, while for the remaining 5 EROs the analysis is based on photometric redshifts. We find evidence for the presence of an X-ray obscured QSO in at least 5 out of the 6 X-ray emitting EROs. For these 5 objects we derive intrinsic (2-10 keV) luminosities in excess of 1044 ergs-1 and intrinsic column densities higher than 1022 cm-2. These values have been obtained through a basic X-ray spectral analysis for the three brightest sources and through the analysis of the hardness ratios for the remaining two. All of these 5 X-ray emitting EROs appear extended in the optical/near-infrared bands indicating that the host galaxy emission dominates at these wavelengths. This suggests that the hosted AGNs are likely to be absorbed also in the optical/near-infrared bands: i.e. they are likely X-ray obscured possible type 2 QSOs. For the remaining ERO the presence of an AGN is suggested both by its high 0.5-2 keV luminosity (L 0.5-2kev ? 1043 erg s-1) and by its X-rayto-optical flux ratio. In this case the quality of the present data prevents us from placing firm constraints on the AGN type hosted. Finally, the near-IR spectrum obtained for one of the 6 EROs classifies the host galaxy as an elliptical at z ? 1.7 with a stellar mass well in excess of 10 11 M?. This result corroborates the possible link between the QSO activity and the formation of massive spheroids.
Filiaciones:
Severgnini P.:
Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy
Delia Ceca R.:
Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy
Braito V.:
Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy
Saracco P.:
Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy
Longhetti M.:
Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy
Bender R.:
Universitats-Sternwarte München, Schemer Str. 1, 81679 München, Germany
Max-Planck-Inst. F. E., Giessenbachstraße, 85748 Garching, Germany
Drory N.:
University of Texas at Austin, Austin, TX 78712, United States
Feulner G.:
Universitats-Sternwarte München, Schemer Str. 1, 81679 München, Germany
Hopp U.:
Universitats-Sternwarte München, Schemer Str. 1, 81679 München, Germany
Max-Planck-Inst. F. E., Giessenbachstraße, 85748 Garching, Germany
Mannucci F.:
IRA, CNR, Firenze, Italy
Maraston C.:
Max-Planck-Inst. F. E., Giessenbachstraße, 85748 Garching, Germany
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