Volume 522, November 2010
|Number of page(s)||4|
|Published online||27 October 2010|
Letter to the Editor
The MBH − Mstar relation of obscured AGNs at high redshift⋆
Dipartimento di FisicaUniversità Roma Tre, via della Vasca Navale 84, 00146
2 INAF - Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy
3 Dipartimento di Astronomia, Università degli Studi di Bologna, via Ranzani1, 40127 Bologna, Italy
4 INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
5 Dipartimento Fisica e Astronomia, Università degli Studi di Firenze, Largo E. Fermi 2, 50125 Firenze, Italy
Accepted: 4 October 2010
We report the detection of broad Hα emission in three X-ray selected obscured AGNs at z ~ 1–2. By exploiting the Hα width and the intrinsic X-ray luminosity, we estimate their black hole masses, which are in the range 0.1–3 × 109 M⊙. By means of multi-band photometric data, we measure the stellar mass of their host galaxy and, therefore, infer their MBH/Mstar ratio. These are the first obscured AGNs at high-z, selected based on their black hole accretion (i.e. on the basis of their X-ray luminosity), that can be located on the MBH − Mstar relation at high-z. All of these obscured high-z AGNs are fully consistent with the local MBH − Mstar relation. This result conflicts with those for other samples of AGNs in the same redshift range, whose MBH/Mstar ratio departs significantly from the value observed in local galaxies. We suggest that the obscured AGNs in our sample are in an advanced evolutionary stage, have already settled onto the local MBH-Mstar relation, and whose nuclear activity has been temporarily revived by recent galaxy interactions.
Key words: quasars: emission lines / galaxies: active / infrared: galaxies / X-rays: galaxies / Black hole physics
© ESO, 2010
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