Volume 518, July-August 2010
Herschel: the first science highlights
|Number of page(s)||5|
|Published online||16 July 2010|
Letter to the Editor
Star formation in AGN hosts in GOODS-N *
MPE, Postfach 1312, 85741 Garching, Germany e-mail: firstname.lastname@example.org
2 INAF – Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy
3 Department of Physics, Durham University, South Road, Durham, DH1 3LE, UK
4 European Space Astronomy Centre, Villafranca del Castillo, Spain
5 European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany
6 INAF – Osservatorio Astronomico di Trieste, via Tiepolo 11, 34143 Trieste, Italy
7 IRFU/Service d'Astrophysique, Bât.709, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France
8 Pontificia Universidad Católica de Chile, Departamento de Astronomía y Astrofísica, Casilla 306, Santiago 22, Chile
9 Instituto de Astrofísica de Canarias, 38205 La Laguna, Spain
10 Departamento de Astrofísica, Universidad de La Laguna, Spain
11 Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802, USA
12 Istituto Nazionale di Astronomia, Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
13 Dipartimento di Astronomia, Universitá di Padova, 35122 Padova, Italy
14 Max-Planck-Institut für Plasmaphysik, Boltzmannstraße 2, 85748 Garching, Germany
Accepted: 13 May 2010
Sensitive Herschel far-infrared observations can break degeneracies that were inherent to previous studies of star formation in high-z AGN hosts. Combining PACS 100 and 160 μm observations of the GOODS-N field with 2 Ms Chandra data, we detect ~20% of X-ray AGN individually at >3σ. The host far-infrared luminosity of AGN with ≈ 1043 erg s-1 increases with redshift by an order of magnitude from z = 0 to z ∼ 1. In contrast, there is little dependence of far-infrared luminosity on AGN luminosity, for 1044 erg s-1 AGN at z 1. We do not find a dependence of far-infrared luminosity on X-ray obscuring column, for our sample which is dominated by < 1044 erg s-1 AGN. In conjunction with properties of local and luminous high-z AGN, we interpret these results as reflecting the interplay between two paths of AGN/host coevolution. A correlation of AGN luminosity and host star formation is traced locally over a wide range of luminosities and also extends to luminous high-z AGN. This correlation reflects an evolutionary connection, likely via merging. For lower AGN luminosities, star formation is similar to that in non-active massive galaxies and shows little dependence on AGN luminosity. The level of this secular, non-merger driven star formation increasingly dominates over the correlation at increasing redshift.
Key words: galaxies: active / infrared: galaxies
© ESO, 2010
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