Warm Molecular Gas in Luminous Infrared Galaxies
Creators
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Infrared Processing and Analysis Center
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Purple Mountain Observatory
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Chinese Academy of Sciences
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California Institute of Technology
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University of Crete
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National Observatory of Athens
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Paris Observatory
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University of Virginia
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National Radio Astronomy Observatory
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NOIRLab
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University of Barcelona
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University of Oxford
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University of Hawaii at Manoa
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14.
Leiden University
Abstract
We present our initial results on the CO rotational spectral line energy distribution (SLED) of the J to J−1 transitions from J = 4 up to 13 from Herschel SPIRE spectroscopic observations of 65 luminous infrared galaxies (LIRGs) in the Great Observatories All-Sky LIRG Survey (GOALS). The observed SLEDs change on average from one peaking at J ≤ 4 to a broad distribution peaking around J ~6−7 as the IRAS 60-to-100μm color, C(60/100), increases. However, the ratios of a CO line luminosity to the total infrared luminosity, L_(IR), show the smallest variation for J around 6 or 7. This suggests that, for most LIRGs, ongoing star formation (SF) is also responsible for a warm gas component that emits CO lines primarily in the mid-J regime (5 ≾ J ≾ 10). As a result, the logarithmic ratios of the CO line luminosity summed over CO(5−4), (6−5), (7−6), (8−7) and (10−9) transitions to L_(IR), log R_(midCO), remain largely independent of C(60/100), and show a mean value of −4.13 (≡ log R^(SF)_(midCO)) and a sample standard deviation of only 0.10 for the SF-dominated galaxies. Including additional galaxies from the literature, we show, albeit with small number of cases, the possibility that galaxies, which bear powerful interstellar shocks unrelated to the current SF, and galaxies, in which an energetic active galactic nucleus contributes significantly to the bolometric luminosity, have their R_(midCO) higher and lower than R^(SF)_(midCO), respectively.
Additional Information
© 2014 American Astronomical Society. Received 2014 March 25; accepted 2014 May 1; published 2014 May 13. Based on Herschel observations. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. This Letter benefited from a number of useful comments made by an anonymous referee. This work is based in part on observations made with Herschel, a European Space Agency Cornerstone Mission with significant participation by NASA. Support for this work was provided in part by NASA through an award issued by JPL/Caltech. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA.Attached Files
Published - 2041-8205_787_2_L23.pdf
Submitted - 1405.0313.pdf
Files
1405.0313.pdf
Additional details
Identifiers
- Eprint ID
- 45833
- Resolver ID
- CaltechAUTHORS:20140520-090210121
Related works
- Describes
- http://arxiv.org/abs/1405.0313 (URL)
Funding
- NASA/JPL/Caltech
Dates
- Created
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2014-05-28Created from EPrint's datestamp field
- Updated
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2021-11-10Created from EPrint's last_modified field
Caltech Custom Metadata
- Caltech groups
- Infrared Processing and Analysis Center (IPAC)