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Morphologies of z ∼ 0.7 AGN host galaxies in CANDELS: no trend of merger incidence with AGN luminosity

Villforth, C. and Hopkins, P. F. (2014) Morphologies of z ∼ 0.7 AGN host galaxies in CANDELS: no trend of merger incidence with AGN luminosity. Monthly Notices of the Royal Astronomical Society, 439 (4). pp. 3342-3356. ISSN 0035-8711.

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The processes that trigger active galactic nuclei (AGN) remain poorly understood. While lower luminosity AGN may be triggered by minor disturbances to the host galaxy, stronger disturbances are likely required to trigger luminous AGN. Major wet mergers of galaxies are ideal environments for AGN triggering since they provide large gas supplies and galaxy scale torques. There is however little observational evidence for a strong connection between AGN and major mergers. We analyse the morphological properties of AGN host galaxies as a function of AGN and host galaxy luminosity and compare them to a carefully matched sample of control galaxies. AGN are X-ray selected in the redshift range 0.5 < z < 0.8 and have luminosities 41 ≲ log (L_X [erg s^(−1)]) ≲ 44.5. ‘Fake AGN’ are simulated in the control galaxies by adding point sources with the magnitude of the matched AGN. We find that AGN host and control galaxies have comparable asymmetries, Sérsic indices and ellipticities at rest frame ∼950 nm. AGN host galaxies show neither higher average asymmetries nor higher fractions of very disturbed objects. There is no increase in the prevalence of merger signatures with AGN luminosity. At 95 per cent confidence we find that major mergers are responsible for <6 per cent of all AGN in our sample as well as <40 per cent of the highest luminosity AGN (log  (L_X [erg s^(−1)]) ∼ 43.5). Major mergers therefore either play only a very minor role in the triggering of AGN in the luminosity range studied or time delays are too long for merger features to remain visible.

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Hopkins, P. F.0000-0003-3729-1684
Additional Information:© 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2014 January 20. Received 2014 January 17; in original form 2013 October 28. First published online: February 27, 2014. We thank the anonymous referee for helpful comments. This work was supported in part by the USA National Science Foundation grant AST-1009628. This work is based on observations taken by the CANDELS Multi-Cycle Treasury Program with the NASA ESA HST, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for Program number HST-GO-12060 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. PS would like to acknowledge funding through grant ASI I/005/11/0. DKoo would like to acknowledge funding through grant NSF AST-0808133. SJ acknowledges financial support from the EC through an ERC grant StG-257720. For all statistical tests as well as estimation of probability density functions for statistical distribution, we use SCIPY statistical packages.
Funding AgencyGrant Number
Agenzia Spaziale Italiana (ASI)I/005/11/0
European Research Council (ERC)StG-257720
Subject Keywords:galaxies: active galaxies: evolution galaxies: interactions galaxies: irregular quasars: general
Issue or Number:4
Record Number:CaltechAUTHORS:20140602-065803046
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Official Citation:C. Villforth, F. Hamann, D. J. Rosario, P. Santini, E. J. McGrath, A. van der Wel, Y. Y. Chang, Y. Guo, T. Dahlen, E. F. Bell, C. J. Conselice, D. Croton, A. Dekel, S. M. Faber, N. Grogin, T. Hamilton, P. F. Hopkins, S. Juneau, J. Kartaltepe, D. Kocevski, A. Koekemoer, D. C. Koo, J. Lotz, D. McIntosh, M. Mozena, R. Somerville, and V. Wild Morphologies of z ∼ 0.7 AGN host galaxies in CANDELS: no trend of merger incidence with AGN luminosity MNRAS (April 21, 2014) Vol. 439 3342-3356 first published online February 27, 2014 doi:10.1093/mnras/stu173
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46022
Deposited By: Ruth Sustaita
Deposited On:02 Jun 2014 15:11
Last Modified:03 Oct 2019 06:39

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