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The Role of Star Formation and AGN in Dust Heating of z=0.3-2.8 Galaxies - II. Informing IR AGN Fraction Estimates through Simulations

Roebuck, Eric and Sajina, Anna and Hayward, Christopher C. and Pope, Alexandra and Kirkpatrick, Allison and Hernquist, Lars and Yan, Lin (2016) The Role of Star Formation and AGN in Dust Heating of z=0.3-2.8 Galaxies - II. Informing IR AGN Fraction Estimates through Simulations. Astrophysical Journal, 833 (1). Art. No. 60. ISSN 0004-637X.

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A key question in extragalactic studies is the determination of the relative roles of stars and active galactic nuclei (AGNs) in powering dusty galaxies at z ~ 1–3 where the bulk of star formation and AGN activity took place. In Paper I, we present a sample of 336 24 μm selected (Ultra)Luminous Infrared Galaxies, (U)LIRGs, at z ~ 0.3–2.8, where we focus on determining the AGN contribution to the IR luminosity. Here, we use hydrodynamic simulations with dust radiative transfer of isolated and merging galaxies to investigate how well the simulations reproduce our empirical IR AGN fraction estimates and determine how IR AGN fractions relate to the UV-mm AGN fraction. We find that: (1) IR AGN fraction estimates based on simulations are in qualitative agreement with the empirical values when host reprocessing of the AGN light is considered; (2) for star-forming galaxy (SFG)–AGN composites our empirical methods may be underestimating the role of AGN, as our simulations imply >50% AGN fractions, ~3x higher than previous estimates; (3) 6% of our empirically classified SFGs have AGN fractions ≳50%. While this is a small percentage of SFGs, if confirmed it would imply that the true number density of AGNs may be underestimated; (4) this comparison depends on the adopted AGN template—those that neglect the contribution of warm dust lower the empirical fractions by up to two times; and (5) the IR AGN fraction is only a good proxy for the intrinsic UV-mm AGN fraction when the extinction is high (A_V ≳ 1 or up to and including coalescence in a merger).

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Sajina, Anna0000-0002-1917-1200
Hayward, Christopher C.0000-0003-4073-3236
Pope, Alexandra0000-0001-8592-2706
Hernquist, Lars0000-0001-6950-1629
Yan, Lin0000-0003-1710-9339
Additional Information:© 2016 The American Astronomical Society. Received 2016 April 19; revised 2016 September 27; accepted 2016 October 1; published 2016 December 7. We are grateful to the anonymous referee for their careful reading and detailed feedback that improved the content and presentation of this paper. This work is supported by NSF grants AST-1313206 and AST-1312418. C.C.H. is grateful to the Gordon and Betty Moore Foundation for financial support. This work is based in part on data obtained with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. This work also makes use of Herschel data. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
Subject Keywords:galaxies: active – galaxies: evolution – galaxies: starburst – infrared: galaxies – quasars: supermassive black holes
Issue or Number:1
Record Number:CaltechAUTHORS:20161209-092345033
Persistent URL:
Official Citation:Eric Roebuck et al 2016 ApJ 833 60
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:72687
Deposited By: Tony Diaz
Deposited On:09 Dec 2016 19:35
Last Modified:03 Oct 2019 16:20

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