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CANDELS : constraining the AGN-merger connection with host morphologies at z ∼ 2

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Abstract
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 similar to 2. Our sample consists of 72 moderate-luminosity (L-X similar to 10(42-44) erg s(-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(-5.9)(+5.8)%), while a smaller percentage are found in spheroids (27.8(-4.6)(+5.8)%). Roughly 16.7(-3.5)(+5.3)% 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(-5.9)(+5.6)%) 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 similar to 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 similar to 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 similar to 2 than previously thought.
Keywords
ACTIVE GALACTIC NUCLEI, DEEP FIELD-SOUTH, QUASAR LUMINOSITY FUNCTION, SUPERMASSIVE BLACK-HOLES, EXTENDED GROTH STRIP, MS SOURCE CATALOGS, FAINT X-RAY, GALAXY MERGERS, STAR-FORMATION, HIGH-REDSHIFT, galaxies: active, galaxies: evolution, X-rays: galaxies

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Chicago
Kocevski, Dale D, SM Faber, Mark Mozena, Anton M Koekemoer, Kirpal Nandra, Cyprian Rangel, Elise S Laird, et al. 2012. “CANDELS : Constraining the AGN-merger Connection with Host Morphologies at z ∼ 2.” Astrophysical Journal 744 (2).
APA
Kocevski, D. D., Faber, S., Mozena, M., Koekemoer, A. M., Nandra, K., Rangel, C., Laird, E. S., et al. (2012). CANDELS : constraining the AGN-merger connection with host morphologies at z ∼ 2. ASTROPHYSICAL JOURNAL, 744(2).
Vancouver
1.
Kocevski DD, Faber S, Mozena M, Koekemoer AM, Nandra K, Rangel C, et al. CANDELS : constraining the AGN-merger connection with host morphologies at z ∼ 2. ASTROPHYSICAL JOURNAL. 2012;744(2).
MLA
Kocevski, Dale D, SM Faber, Mark Mozena, et al. “CANDELS : Constraining the AGN-merger Connection with Host Morphologies at z ∼ 2.” ASTROPHYSICAL JOURNAL 744.2 (2012): n. pag. Print.
@article{8575190,
  abstract     = {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 similar to 2. Our sample consists of 72 moderate-luminosity (L-X similar to 10(42-44) erg s(-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(-5.9)(+5.8)%), while a smaller percentage are found in spheroids (27.8(-4.6)(+5.8)%). Roughly 16.7(-3.5)(+5.3)% 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(-5.9)(+5.6)%) 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 similar to 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 similar to 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 similar to 2 than previously thought.},
  articleno    = {148},
  author       = {Kocevski, Dale D and Faber, SM and Mozena, Mark and Koekemoer, Anton M and Nandra, Kirpal and Rangel, Cyprian and Laird, Elise S and Brusa, Marcella and Wuyts, Stijn and Trump, Jonathan R and Koo, David C and Somerville, Rachel S and Bell, Eric F and Lotz, Jennifer M and Alexander, David M and Bournaud, Frederic and Conselice, Christopher J and Dahlen, Tomas and Dekel, Avishai and Donley, Jennifer L and Dunlop, James S and Finoguenov, Alexis and Georgakakis, Antonis and Giavalisco, Mauro and Guo, Yicheng and Grogin, Norman A and Hathi, Nimish P and Juneau, Stephanie and Kartaltepe, Jeyhan S and Lucas, Ray A and McGrath, Elizabeth J and McIntosh, Daniel H and Mobasher, Bahram and Robaina, Aday R and Rosario, David and Straughn, Amber N and van der Wel, Arjen and Villforth, Carolin},
  issn         = {0004-637X},
  journal      = {ASTROPHYSICAL JOURNAL},
  keywords     = {ACTIVE GALACTIC NUCLEI,DEEP FIELD-SOUTH,QUASAR LUMINOSITY FUNCTION,SUPERMASSIVE BLACK-HOLES,EXTENDED GROTH STRIP,MS SOURCE CATALOGS,FAINT X-RAY,GALAXY MERGERS,STAR-FORMATION,HIGH-REDSHIFT,galaxies: active,galaxies: evolution,X-rays: galaxies},
  language     = {eng},
  number       = {2},
  pages        = {9},
  title        = {CANDELS : constraining the AGN-merger connection with host morphologies at z ∼ 2},
  url          = {http://dx.doi.org/10.1088/0004-637X/744/2/148},
  volume       = {744},
  year         = {2012},
}

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