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
Abstract
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).
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.Attached Files
Published - Roebuck_2016_ApJ_833_60.pdf
Submitted - 1609.08660v2.pdf
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Additional details
- Eprint ID
- 72687
- Resolver ID
- CaltechAUTHORS:20161209-092345033
- AST-1313206
- NSF
- AST-1312418
- NSF
- Gordon and Betty Moore Foundation
- NASA/JPL/Caltech
- Created
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2016-12-09Created from EPrint's datestamp field
- Updated
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2021-11-11Created from EPrint's last_modified field
- Caltech groups
- Infrared Processing and Analysis Center (IPAC)