CANDELS: CONSTRAINING THE AGN-MERGER CONNECTION WITH HOST MORPHOLOGIES AT z {approx} 2

Journal Article · Tue Jan 10 00:00:00 EST 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/744/2/148· OSTI ID:22004202

Kocevski, Dale D; Faber, S M; Mozena, Mark; Trump, Jonathan R; Koo, David C ^[1]; Koekemoer, Anton M; Somerville, Rachel S; Lotz, Jennifer M; Dahlen, Tomas; Donley, Jennifer L ^[2]; Nandra, Kirpal; Brusa, Marcella; Wuyts, Stijn ^[3]; Rangel, Cyprian; Laird, Elise S ^[4]; Bell, Eric F ^[5]; Alexander, David M ^[6]; Bournaud, Frederic ^[7]; Conselice, Christopher J ^[8]; Dekel, Avishai ^[9] ; others, and

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1. University of California Observatories/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States)
2. Space Telescope Science Institute, Baltimore, MD 21218 (United States)
3. Max-Planck-Institut fuer extraterrestrische Physik, D-85748 Garching (Germany)
4. Astrophysics Group, Imperial College London, London, SW7 2AZ (United Kingdom)
5. Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States)
6. Department of Physics, Durham University, Durham DH1 3LE (United Kingdom)
7. CEA, IRFU, SAp and Laboratoire AIM Paris-Saclay, F-91191 Gif-sur-Yvette (France)
8. Centre for Astronomy and Particle Theory, University of Nottingham, Nottingham, NG7 2RD (United Kingdom)
9. Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904 (Israel)

Using Hubble Space Telescope/WFC3 imaging taken as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we examine the role that major galaxy mergers play in triggering active galactic nucleus (AGN) activity at z {approx} 2. Our sample consists of 72 moderate-luminosity (L{sub X} {approx} 10{sup 42-44} erg s{sup -1}) AGNs at 1.5 < z < 2.5 that are selected using the 4 Ms Chandra observations in the Chandra Deep Field South, the deepest X-ray observations to date. Employing visual classifications, we have analyzed the rest-frame optical morphologies of the AGN host galaxies and compared them to a mass-matched control sample of 216 non-active galaxies at the same redshift. We find that most of the AGNs reside in disk galaxies (51.4{sup +5.8}{sub -5.9}%), while a smaller percentage are found in spheroids (27.8{sup +5.8}{sub -4.6}%). Roughly 16.7{sup +5.3}{sub -3.5}% of the AGN hosts have highly disturbed morphologies and appear to be involved in a major merger or interaction, while most of the hosts (55.6{sup +5.6}{sub -5.9}%) appear relatively relaxed and undisturbed. These fractions are statistically consistent with the fraction of control galaxies that show similar morphological disturbances. These results suggest that the hosts of moderate-luminosity AGNs are no more likely to be involved in an ongoing merger or interaction relative to non-active galaxies of similar mass at z {approx} 2. The high disk fraction observed among the AGN hosts also appears to be at odds with predictions that merger-driven accretion should be the dominant AGN fueling mode at z {approx} 2, even at moderate X-ray luminosities. Although we cannot rule out that minor mergers are responsible for triggering these systems, the presence of a large population of relatively undisturbed disk-like hosts suggests that the stochastic accretion of gas plays a greater role in fueling AGN activity at z {approx} 2 than previously thought.

• OSTI ID: 22004202
• Journal Information: Astrophysical Journal, Vol. 744, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
CLASSIFICATION
GALACTIC EVOLUTION
LUMINOSITY
MORPHOLOGY
RED SHIFT
SPHEROIDS
STOCHASTIC PROCESSES
TELESCOPES
X-RAY GALAXIES