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Measuring Star Formation and Black Hole Accretion Rates in Tandem Using Mid-infrared Spectra of Local Infrared Luminous Galaxies

Stone, Meredith and Pope, Alexandra and McKinney, Jed and Armus, Lee and Díaz-Santos, Tanio and Inami, Hanae and Kirkpatrick, Allison and Stierwalt, Sabrina (2022) Measuring Star Formation and Black Hole Accretion Rates in Tandem Using Mid-infrared Spectra of Local Infrared Luminous Galaxies. Astrophysical Journal, 934 (1). Art. No. 27. ISSN 0004-637X. doi:10.3847/1538-4357/ac778b.

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We present the results of a stacking analysis performed on Spitzer/Infrared Spectrograph high-resolution mid-infrared (mid-IR) spectra of luminous infrared galaxies (LIRGs) in the Great Observatories All-Sky LIRG Survey. By binning in relation to mid-IR active galactic nucleus (AGN) fraction and stacking spectra, we detect bright emission lines [Ne ii] and [Ne iii], which trace star formation, and fainter emission lines [Ne v] and [O iv], which trace AGN activity, throughout the sample. We find that the [Ne ii] luminosity is fairly constant across all AGN fraction bins, while the [O iv] and [Ne v] luminosities increase by over an order of magnitude. Our measured average line ratios, [Ne v]/[Ne ii] and [O iv]/[Ne ii], at low AGN fraction are similar to H II galaxies, while the line ratios at high AGN fraction are similar to LINERs and Seyferts. We decompose the [O iv] luminosity into star formation and AGN components by fitting the [O iv] luminosity as a function of the [Ne ii] luminosity and the mid-IR AGN fraction. The [O iv] luminosity in LIRGs is dominated by star formation for mid-IR AGN fractions ≲ 0.3. With the corrected [O iv] luminosity, we calculate black hole accretion rates (BHARs) ranging from 10⁻⁵ M_⊙ yr⁻¹ at low AGN fractions to 0.2 M_⊙ yr⁻¹ at the highest AGN fractions. We find that using the [O iv] luminosity, without correcting for star formation, can lead to overestimation of the BHAR by up to a factor of 30 in starburst-dominated LIRGs. Finally, we show that the BHAR/star formation rate ratio increases by more than three orders of magnitude as a function of mid-IR AGN fraction in LIRGs.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Stone, Meredith0000-0002-9720-3255
Pope, Alexandra0000-0001-8592-2706
McKinney, Jed0000-0002-6149-8178
Armus, Lee0000-0003-3498-2973
Díaz-Santos, Tanio0000-0003-0699-6083
Inami, Hanae0000-0003-4268-0393
Kirkpatrick, Allison0000-0002-5537-8110
Stierwalt, Sabrina0000-0002-2596-8531
Additional Information:© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 December 14; revised 2022 April 15; accepted 2022 June 8; published 2022 July 21. We thank the referee for the constructive comments that improved this work. We thank Krista Gile for advice regarding statistics and error analysis. M.S. is grateful for support from the Massachusetts Space Grant consortium, the Commonwealth Honors College, and the Five College Astronomy Department. This research has made use of the NASA/IPAC Infrared Science Archive, which is funded by the National Aeronautics and Space Administration and operated by the California Institute of Technology. We thank the IRSA staff for help with the GOALS IRS data products.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Massachusetts Space Grant ConsortiumUNSPECIFIED
Commonwealth Honors CollegeUNSPECIFIED
Five College Astronomy DepartmentUNSPECIFIED
Subject Keywords:Luminous infrared galaxies; Ultraluminous infrared galaxies; Supermassive black holes; Star formation; Galaxy evolution
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Luminous infrared galaxies (946); Ultraluminous infrared galaxies (1735); Supermassive black holes (1663); Star formation (1569); Galaxy evolution (594)
Record Number:CaltechAUTHORS:20220726-997759000
Persistent URL:
Official Citation:Meredith Stone et al 2022 ApJ 934 27
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115858
Deposited By: George Porter
Deposited On:27 Jul 2022 21:01
Last Modified:27 Jul 2022 21:01

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