THE BULK OF THE BLACK HOLE GROWTH SINCE z {approx} 1 OCCURS IN A SECULAR UNIVERSE: NO MAJOR MERGER-AGN CONNECTION

Journal Article · Mon Jan 10 04:00:00 EST 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/726/2/57· OSTI ID:21567680

Cisternas, Mauricio; Jahnke, Knud; Inskip, Katherine J; Robaina, Aday R; Andrae, Rene ^[1]; Kartaltepe, Jeyhan ^[2]; Koekemoer, Anton M ^[3]; Lisker, Thorsten ^[4]; Scodeggio, Marco ^[5]; Sheth, Kartik; Capak, Peter ^[6]; Trump, Jonathan R; Impey, Chris D ^[7]; Miyaji, Takamitsu ^[8]; Lusso, Elisabeta ^[9]; Brusa, Marcella; Cappelluti, Nico ^[10]; Civano, Francesca ^[11]; Ilbert, Olivier ^[12]; Leauthaud, Alexie ^[13]

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1. Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)
2. National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85 721 (United States)
3. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
4. Astronomisches Rechen-Institut, Zentrum fuer Astronomie der Universitaet Heidelberg, Moenchhofstr. 12-14, D-69120 Heidelberg (Germany)
5. IASF-INAF, Via Bassini 15, I-20133 Milano (Italy)
6. California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, CA 91125 (United States)
7. Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
8. Instituto de AstronomIa, Universidad Nacional Autonoma de Mexico, Ensenada, Mexico (P.O. Box 439027, San Diego, CA 92143-9027, USA) (United States)
9. INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy)
10. Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching bei Muenchen (Germany)
11. Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
12. Laboratoire d'Astrophysique de Marseille, BP 8, Traverse du Siphon, F-13376 Marseille Cedex 12 (France)
13. LBNL and Berkeley Center for Cosmological Physics, University of California, CA 94720 (United States)

What is the relevance of major mergers and interactions as triggering mechanisms for active galactic nuclei (AGNs) activity? To answer this long-standing question, we analyze 140 XMM-Newton-selected AGN host galaxies and a matched control sample of 1264 inactive galaxies over z {approx} 0.3-1.0 and M{sub *} < 10{sup 11.7} M{sub sun} with high-resolution Hubble Space Telescope/Advanced Camera for Surveys imaging from the COSMOS field. The visual analysis of their morphologies by 10 independent human classifiers yields a measure of the fraction of distorted morphologies in the AGN and control samples, i.e., quantifying the signature of recent mergers which might potentially be responsible for fueling/triggering the AGN. We find that (1) the vast majority (>85%) of the AGN host galaxies do not show strong distortions and (2) there is no significant difference in the distortion fractions between active and inactive galaxies. Our findings provide the best direct evidence that, since z {approx} 1, the bulk of black hole (BH) accretion has not been triggered by major galaxy mergers, therefore arguing that the alternative mechanisms, i.e., internal secular processes and minor interactions, are the leading triggers for the episodes of major BH growth. We also exclude an alternative interpretation of our results: a substantial time lag between merging and the observability of the AGN phase could wash out the most significant merging signatures, explaining the lack of enhancement of strong distortions on the AGN hosts. We show that this alternative scenario is unlikely due to (1) recent major mergers being ruled out for the majority of sources due to the high fraction of disk-hosted AGNs, (2) the lack of a significant X-ray signal in merging inactive galaxies as a signature of a potential buried AGN, and (3) the low levels of soft X-ray obscuration for AGNs hosted by interacting galaxies, in contrast to model predictions.

• OSTI ID: 21567680
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 726; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BLACK HOLES
GALAXIES
GALAXY NUCLEI
GROWTH
MORPHOLOGY
UNIVERSE