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Warm Molecular Hydrogen in Nearby, Luminous Infrared Galaxies

Petric, Andreea O. and Armus, Lee and Flagey, Nicolas and Guillard, Pierre and Howell, Justin and Inami, Hanae and Charmandaris, Vassillis and Evans, Aaron and Stierwalt, Sabrina and Diaz-Santos, Tanio and Lu, Nanyao and Spoon, Henrik and Mazzarella, Joe and Appleton, Phil and Chan, Ben and Chu, Jason and Hand, Derek and Privon, George and Sanders, David and Surace, Jason and Xu, Kevin and Zhao, Yinghe (2018) Warm Molecular Hydrogen in Nearby, Luminous Infrared Galaxies. Astronomical Journal, 156 (6). Art. No. 295. ISSN 1538-3881. doi:10.3847/1538-3881/aaca35.

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Mid-infrared molecular hydrogen (H_2) emission is a powerful cooling agent in galaxy mergers and in radio galaxies; it is a potential key tracer of gas evolution and energy dissipation associated with mergers, star formation, and accretion onto supermassive black holes. We detect mid-IR H_2 line emission in at least one rotational transition in 91% of the 214 Luminous Infrared Galaxies (LIRGs) observed with Spitzer as part of the Great Observatories All-sky LIRG Survey. We use H_2 excitation diagrams to estimate the range of masses and temperatures of warm molecular gas in these galaxies. We find that LIRGs in which the IR emission originates mostly from the Active Galactic Nuclei (AGN) have about 100 K higher H_2 mass-averaged excitation temperatures than LIRGs in which the IR emission originates mostly from star formation. Between 10% and 15% of LIRGs have H_2 emission lines that are sufficiently broad to be resolved or partially resolved by the high-resolution modules of Spitzer's Infrared Spectrograph (IRS). Those sources tend to be mergers and contain AGN. This suggests that a significant fraction of the H_2 line emission is powered by AGN activity through X-rays, cosmic rays, and turbulence. We find a statistically significant correlation between the kinetic energy in the H2 gas and the H_2 to IR luminosity ratio. The sources with the largest warm gas kinetic energies are mergers. We speculate that mergers increase the production of bulk inflows leading to observable broad H_2 profiles and possibly denser gas.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Petric, Andreea O.0000-0003-4030-3455
Armus, Lee0000-0003-3498-2973
Flagey, Nicolas0000-0002-8763-1555
Guillard, Pierre0000-0002-2421-1350
Inami, Hanae0000-0003-4268-0393
Charmandaris, Vassillis0000-0002-2688-1956
Evans, Aaron0000-0003-2638-1334
Stierwalt, Sabrina0000-0002-2596-8531
Diaz-Santos, Tanio0000-0003-0699-6083
Lu, Nanyao0000-0002-8948-1044
Spoon, Henrik0000-0002-8712-369X
Mazzarella, Joe0000-0002-8204-8619
Appleton, Phil0000-0002-7607-8766
Chu, Jason0000-0003-3955-2470
Privon, George0000-0003-3474-1125
Sanders, David0000-0002-1233-9998
Surace, Jason0000-0001-7291-0087
Xu, Kevin0000-0002-1588-6700
Zhao, Yinghe0000-0002-9128-818X
Additional Information:© 2018. The American Astronomical Society. Received 2017 April 6; revised 2018 April 18; accepted 2018 April 26; published 2018 December 5. This work is based primarily on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. We have made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Support for this research was provided by NASA through an award issued by JPL/Caltech. V.C. would like to acknowledge partial support from the EU FP7 Grant PIRSES-GA-2012-316788. A.P. thanks T. Geballe for comments that improved the clarity of the paper. N.L. acknowledges support by the NSFC grant #11673028 and National Key R&D Program of China grant #2017YFA0402704.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Marie Curie FellowshipPIRSES-GA-2012-316788
National Natural Science Foundation of China11673028
National Key Research and Development Program of China2017YFA0402704
Subject Keywords:galaxies: active; galaxies: interactions; galaxies: ISM; galaxies: starburst
Issue or Number:6
Record Number:CaltechAUTHORS:20181205-114248648
Persistent URL:
Official Citation:Andreea O. Petric et al 2018 AJ 156 295
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:91506
Deposited By: George Porter
Deposited On:05 Dec 2018 21:57
Last Modified:16 Nov 2021 03:41

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