The host galaxies of X-ray selected active galactic nuclei to z = 2.5: Structure, star formation, and their relationships from CANDELS and Herschel/PACS^⋆,⋆⋆

¹ Max-Planck-Institut für Extraterrestrische Physik (MPE), Postfach 1312, 85741 Garching, Germany
² Department of Physics & Astronomy, University of Missouri-Kansas City, 5110 Rockhill Rd., Kansas City, MO 64110, USA
³ Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁴ National Optical Astronomy Observatory, 950 N. Cherry Ave., Tucson, AZ 85719, USA
⁵ INAF–Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy
⁶ Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA, USA
⁷ Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
⁸ Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Catòlica de Chile, 306, Santiago 22, Chile
⁹ Department of Astronomy, University of Michigan, 500 Church St., Ann Arbor, MI 48109, USA
¹⁰ Department of Astronomy & Astrophysics, The Pennsylvania State University, University Park, Pennsylvania, PA 16802, USA
¹¹ The School of Physics and Astronomy, University of Nottingham, Nottingham, UK
¹² Racah Institute of Physics, The Hebrew University, Jerusalem, Israel
¹³ University of California Observatories/Lick Observatory, University of California, Santa Cruz, CA 95064, USA
¹⁴ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹⁵ Department of Physics and Astronomy, University of Kentucky, Lexington KY 40506-0055, USA
¹⁶ Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany
¹⁷ Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3, OHA, UK
¹⁸ Cavendish Laboratory, University of Cambridge, 19 JJ Thomson Avenue, Cambridge, CB3, OHE, UK
¹⁹ Department of Physics and Astronomy, University ofSheffield, Hounsfield Road, Sheffield S3 7RH, UK
²⁰ Department of Physics and Astronomy, Texas A&M University, College Station, TX, USA
²¹ Exzellenzcluster Universe, Technische Universität München, Boltzmannstrasse 2, 85748 Garching, Germany
²² SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, UK
²³ Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, Colorado 80301, USA
²⁴ Centre for Astrophysics & Supercomputing, Swinburne University of Technology, PO Box 218, Hawthorn, VIC 3122, Australia
²⁵ Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu - CNRS - Université Paris Diderot, CE-Saclay, 91191 Gif-sur-Yvette, France
²⁶ Instituto de Fisica y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Gran Bretaña 1111, Playa Ancha, Valparaíso, Chile
²⁷ Los Alamos National Laboratory, Los Alamos NM 87545, USA
²⁸ Department of Physics and Astronomy, University of California, Riverside, CA 92521, USA
²⁹ Institute for Astronomy, ETH Zurich, Wolgang-Pauli-Strasse 27, 8093 Zurich, Switzerland
³⁰ Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
³¹ School of Mathematics, Statistics & Computer Science, University of KwaZulu-Natal, 4041 Durban, South Africa
³² Department of Physics and Astronomy, Colby College, Waterville, ME 04901, USA
³³ Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
³⁴ Department of Physics and Astronomy, Macalester College, 1600 Grand Avenue, Saint Paul, MN 55105, USA
³⁵ Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
³⁶ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
³⁷ NASA Goddard Space Flight Center, Greenbelt, MD 16418, USA
³⁸ Astronomy Department, 3910 15th Ave NE, University of Washington, Seattle, WA 98195, USA
³⁹ Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611-2055, USA

Received: 7 March 2014
Accepted: 2 October 2014

Abstract

We study the relationship between the structure and star formation rate (SFR) of X-ray selected low and moderate luminosity active galactic nuclei (AGNs) in the two Chandra Deep Fields, using Hubble Space Telescope imaging from the Cosmic Assembly Near Infrared Extragalactic Legacy Survey (CANDELS) and deep far-infrared maps from the PEP+GOODS-Herschel survey. We derive detailed distributions of structural parameters and FIR luminosities from carefully constructed control samples of galaxies, which we then compare to those of the AGNs. At z ~ 1, AGNs show slightly diskier light profiles than massive inactive (non-AGN) galaxies, as well as modestly higher levels of gross galaxy disturbance (as measured by visual signatures of interactions and clumpy structure). In contrast, at z ~ 2, AGNs show similar levels of galaxy disturbance as inactive galaxies, but display a red central light enhancement, which may arise from a more pronounced bulge in AGN hosts or extinguished nuclear light. We undertake a number of tests of both these alternatives, but our results do not strongly favor one interpretation over the other. The mean SFR and its distribution among AGNs and inactive galaxies are similar at z> 1.5. At z< 1, however, clear and significant enhancements are seen in the SFRs of AGNs with bulge-dominated light profiles. These trends suggest an evolution in the relation between nuclear activity and host properties with redshift, towards a minor role for mergers and interactions at z> 1.5.