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Observations of Ultraluminous Infrared Galaxies with the Infrared Spectrograph on the Spitzer Space Telescope. II. The IRAS Bright Galaxy Sample

Armus, L. and Charmandaris, V. and Bernard-Salas, J. and Spoon, H. W. W. and Marshall, J. A. and Higdon, S. J. U. and Desai, V. and Teplitz, H. I. and Hao, L. and Devost, D. and Brandl, B. R. and Wu, Y. and Sloan, G. C. and Soifer, B. T. and Houck, J. R. and Herter, T. L. (2007) Observations of Ultraluminous Infrared Galaxies with the Infrared Spectrograph on the Spitzer Space Telescope. II. The IRAS Bright Galaxy Sample. Astrophysical Journal, 656 (1). pp. 148-167. ISSN 0004-637X. https://resolver.caltech.edu/CaltechAUTHORS:20091014-090138008

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Abstract

We present spectra taken with the Infrared Spectrograph on Spitzer covering the 5-38 μm region of the 10 ultraluminous infrared galaxies (ULIRGs) found in the IRAS Bright Galaxy Sample (BGS). There is a factor of 50 spread in the rest-frame 5.5-60 μm spectral slopes, and the 9.7 μm silicate optical depths range from at least τ_(9.7) ≤ 0.4 (A_V ~ 8) to τ_(9.7) ≥ 4.2 (A_V ≥ 78). There is evidence for water ice and hydrocarbon absorption and C_2H_2 and HCN absorption features in 4 and possibly 6 of the 10 BGS ULIRGs, indicating shielded molecular clouds and a warm, dense ISM. We have detected [Ne V] emission in 3 of the 10 BGS ULIRGs, at flux levels of 5-18 × 10^(-14) ergs cm^(-2) s^(-1) and [Ne V] 14.3/[Ne II] 12.8 line flux ratios of 0.12-0.85. The remaining BGS ULIRGs have limits on their [Ne V]/[Ne II]line flux ratios, which range from ≤0.15 to ≤0.01. Among the BGS ULIRGs, the AGN fractions implied by either the [Ne V]/[Ne II] or [O IV]/[Ne II] line flux ratios (or their upper limits) are significantly lower than implied by the MIR slope or strength of the 6.2 μm PAH EQW feature. There is evidence for hot (T > 300 K) dust in five of the BGS ULIRGs, with the fraction of hot dust to total dust luminosity ranging from ~1% to 23%, before correcting for extinction. When integrated over the IRAC-8, IRS blue peak-up, and MIPS-24 filter bandpasses, the IRS spectra imply very blue colors for some ULIRGs at z ~ 1.3. The large range in diagnostic parameters among the nearest ULIRGs suggests that matching survey results to a small number of templates may lead to biased results about the fraction of luminous dusty starbursts and AGNs at high z.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1086/510107DOIArticle
http://www.iop.org/EJ/abstract/0004-637X/656/1/148/PublisherArticle
ORCID:
AuthorORCID
Teplitz, H. I.0000-0002-7064-5424
Additional Information:© 2007 The American Astronomical Society. Received 2006 October 9; accepted 2006 October 11. We would like to thank Bruce Draine, Aaron Evans, Dean Hines, David Hollenbach, Mark Lacy, Els Peeters, and Jason Surace for many helpful discussions. Support for this work was provided by NASA through an award issued by JPL/Caltech.
Group:Infrared Processing and Analysis Center (IPAC)
Funders:
Funding AgencyGrant Number
NASA/JPL/CaltechUNSPECIFIED
Subject Keywords:galaxies : active; galaxies : starburst; infrared : galaxies
Issue or Number:1
Record Number:CaltechAUTHORS:20091014-090138008
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20091014-090138008
Official Citation:Observations of Ultraluminous Infrared Galaxies with the Infrared Spectrograph on the Spitzer Space Telescope. II. The IRAS Bright Galaxy Sample L. Armus, V. Charmandaris, J. Bernard-Salas, H. W. W. Spoon, J. A. Marshall, S. J. U. Higdon, V. Desai, H. I. Teplitz, L. Hao, D. Devost, B. R. Brandl, Y. Wu, G. C. Sloan, B. T. Soifer, J. R. Houck, and T. L. Herter 2007 ApJ 656 148-167 doi: 10.1086/510107
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16340
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:15 Oct 2009 21:01
Last Modified:03 Oct 2019 01:10

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