Do the most massive black holes at z = 2 grow via major mergers?

Journal Article · Thu Oct 20 04:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/830/2/156· OSTI ID:22868565

Mechtley, M.; Jahnke, K.; Andrae, R.; Van der Wel, A. ^[1]; Windhorst, R. A.; Cohen, S. H. ^[2]; Cisternas, M. ^[3]; Hewlett, T.; Villforth, C. ^[4]; Koekemoer, A. M. ^[5]; Schramm, M.; Schulze, A.; Silverman, J. D. ^[6]; Wisotzki, L. ^[7]

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1. Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany)
2. School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287-1404 (United States)
3. Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife (Spain)
4. Scottish Universities Physics Alliance (SUPA), University of St Andrews, School of Physics and Astronomy, North Haugh, St Andrews, KY16 9SS (United Kingdom)
5. Space Telescope Science Institute, 3700 San Martin Dr, Baltimore, MD 21218 (United States)
6. Kavli Institute for the Physics and Mathematics of the Universe, Todai Institutes for Advanced Study, the University of Tokyo, Kashiwa, 277-8583 (Kavli IPMU, WPI) (Japan)
7. Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany)

The most frequently proposed model for the origin of quasars holds that the high accretion rates seen in luminous active galactic nuclei (AGN) are primarily triggered during major mergers between gas-rich galaxies. While plausible for decades, this model has only begun to be tested with statistical rigor in the past few years. Here, we report on a Hubble Space Telescope study to test this hypothesis for z = 2 quasars with high supermassive black hole masses (M{sub BH}=10{sup 9}--10{sup 10} M{sub ⊙} ), which dominate cosmic black hole growth at this redshift. We compare Wide Field Camera 3 F160W (rest-frame V-band) imaging of 19 point source-subtracted quasar hosts to a matched sample of 84 inactive galaxies, testing whether the quasar hosts have greater evidence for strong gravitational interactions. Using an expert ranking procedure, we find that the quasar hosts are uniformly distributed within the merger sequence of inactive galaxies, with no preference for quasars in high-distortion hosts. Using a merger/non-merger cutoff approach, we recover distortion fractions of f{sub m,qso}=0.39±0.11 for quasar hosts and f{sub m,gal}=0.30±0.05 for inactive galaxies (distribution modes, 68% confidence intervals), with both measurements subjected to the same observational conditions and limitations. The slight enhancement in distorted fraction for quasar hosts over inactive galaxies is not significant, with a probability that the quasar fraction is higher P(f{sub m,qso}>f{sub m,gal})=0.78 (0.78σ), in line with results for lower mass and lower z AGN. We find no evidence that major mergers are the primary triggering mechanism for the massive quasars that dominate accretion at the peak of cosmic quasar activity.

• OSTI ID: 22868565
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 830; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BLACK HOLES
COMPARATIVE EVALUATIONS
DISTRIBUTION
GALAXIES
GALAXY NUCLEI
GRAVITATIONAL INTERACTIONS
MASS
QUASARS
RED SHIFT
SPACE
TELESCOPES