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Mid-Infrared Properties of OH Megamaser Host Galaxies. I. Spitzer IRS Low- and High-Resolution Spectroscopy

Willett, Kyle W. and Darling, Jeremy and Spoon, Henrik W. W. and Charmandaris, Vassilis and Armus, Lee (2011) Mid-Infrared Properties of OH Megamaser Host Galaxies. I. Spitzer IRS Low- and High-Resolution Spectroscopy. Astrophysical Journal Supplement Series, 193 (1). Art. No. 18. ISSN 0067-0049.

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We present mid-infrared spectra and photometry from the Infrared Spectrograph on the Spitzer Space Telescope for 51 OH megamasers (OHMs), along with 15 galaxies confirmed to have no megamaser emission above L_(OH) = 10^(2.3) L_☉. The majority of galaxies display moderate-to-deep 9.7 μm amorphous silicate absorption, with OHM galaxies showing stronger average absorption and steeper 20-30 μm continuum emission than non-masing galaxies. Emission from multiple polycyclic aromatic hydrocarbons (PAHs), especially at 6.2, 7.7, and 11.3 μm, is detected in almost all systems. Fine-structure atomic emission (including [Ne II], [Ne III], [S III], and [S IV]) and multiple H2 rotational transitions are observed in more than 90% of the sample. A subset of galaxies show emission from rarer atomic lines, such as [Ne V], [O IV], and [Fe II]. Fifty percent of the OHMs show absorption from water ice and hydrogenated amorphous carbon grains, while absorption features from CO_2, HCN, C_(2)H_2, and crystalline silicates are also seen in several OHMs. Column densities of OH derived from 34.6 μm OH absorption are similar to those derived from 1667 MHz OH absorption in non-masing galaxies, indicating that the abundance of masing molecules is similar for both samples. This data paper presents full mid-infrared spectra for each galaxy, along with measurements of line fluxes and equivalent widths, absorption feature depths, and spectral indices.

Item Type:Article
Related URLs:
URLURL TypeDescription
Willett, Kyle W.0000-0002-3654-3504
Darling, Jeremy0000-0003-2511-2060
Spoon, Henrik W. W.0000-0002-8712-369X
Charmandaris, Vassilis0000-0002-2688-1956
Armus, Lee0000-0003-3498-2973
Additional Information:© 2011 American Astronomical Society. Received 2010 March 19; accepted 2011 January 26; published 2011 March 3. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through grant 30407 issued by JPL/Caltech. We have made extensive use of theNASA/IPAC Extragalactic Database (NED) which is operated by JPL and Caltech under contract with NASA. Many thanks are due to J.-D. Smith for help with PAHFIT, N. Halverson for comments on computing flux limits, D. Farrah for useful discussions, and to the Spitzer Science Center for hosting K.W.W. and J.D. in 2007 April. V.C. acknowledges partial support from the EU ToK grant 39965 and FP7-REGPOT 206469.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
European Research Council (ERC)FP7-REGPOT 206469
European Research Council (ERC)39965
Subject Keywords:galaxies: active; galaxies: starburst; infrared: galaxies; masers
Issue or Number:1
Classification Code:PACS: 98.54.Cm; 98.65.Fz; 95.30.Ky; 98.58.Bz
Record Number:CaltechAUTHORS:20110421-100803514
Persistent URL:
Official Citation:Kyle W. Willett et al. 2011 ApJS 193 18 doi: 10.1088/0067-0049/193/1/18
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:23411
Deposited By: Jason Perez
Deposited On:21 Apr 2011 18:04
Last Modified:05 Nov 2019 06:13

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