AKARI IRC INFRARED 2.5-5 {mu}m SPECTROSCOPY OF A LARGE SAMPLE OF LUMINOUS INFRARED GALAXIES

Journal Article · Fri Oct 01 04:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/721/2/1233· OSTI ID:21464791

Imanishi, Masatoshi ^[1]; Nakagawa, Takao; Shirahata, Mai ^[2]; Ohyama, Yoichi ^[3]; Onaka, Takashi ^[4]

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1. National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
2. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 252-5210 (Japan)
3. Institute of Astronomy and Astrophysics Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China)
4. Department of Astronomy, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan)

We present the results of our systematic infrared 2.5-5 {mu}m spectroscopy of 60 luminous infrared galaxies (LIRGs) with infrared luminosities L{sub IR} = 10{sup 11}-10{sup 12} L{sub sun} and 54 ultraluminous infrared galaxies (ULIRGs) with L{sub IR} {>=} 10{sup 12} L{sub sun}, using the AKARI Infrared Camera (IRC). AKARI IRC slit-less spectroscopy allows us to probe the full range of emission from these galaxies, including spatially extended components. The 3.3 {mu}m polycyclic aromatic hydrocarbon (PAH) emission features, hydrogen recombination emission lines, and various absorption features are detected and used to investigate the properties of these galaxies. Because of the relatively small effect of dust extinction in the infrared range, quantitative discussion of these dusty galaxy populations is possible. For sources with clearly detectable Br{beta} (2.63 {mu}m) and Br{alpha} (4.05 {mu}m) emission lines, the flux ratios are found to be similar to those predicted by case B theory. Starburst luminosities are estimated from both 3.3 {mu}m PAH and Br{alpha} emission, which roughly agree with each other. In addition to the detected starburst activity, a significant fraction of the observed sources display signatures of obscured active galactic nuclei (AGNs), such as low PAH equivalent widths, large optical depths of dust absorption features, and red continuum emission. The energetic importance of optically elusive buried AGNs in optically non-Seyfert galaxies tends to increase with increasing galaxy infrared luminosity, from LIRGs to ULIRGs.

• OSTI ID: 21464791
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 721; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
AROMATICS
DUSTS
EMISSION
GALAXIES
GALAXY NUCLEI
HYDROCARBONS
LUMINOSITY
OPTICAL PROPERTIES
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
POLYCYCLIC AROMATIC HYDROCARBONS
RECOMBINATION
SEYFERT GALAXIES
SORPTION
SPECTROSCOPY