CO OBSERVATIONS OF THE HOST GALAXY OF GRB 000418 AT z = 1.1

Journal Article · Thu Sep 01 00:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/738/1/33· OSTI ID:21582962

Hatsukade, B; Ohta, K ^[1]; Kohno, K ^[2]; Endo, A ^[3]; Nakanishi, K ^[4]

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1. Department of Astronomy, Kyoto University, Kyoto 606-8502 (Japan)
2. Institute of Astronomy, the University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)
3. Kavli Institute of NanoScience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft (Netherlands)
4. National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

We performed CO (J = 2-1) observations of the host galaxy of GRB 000418 at z = 1.1181 with the Plateau de Bure Interferometer. Previous studies show that the host galaxy has properties similar to those of an ultraluminous infrared galaxy (ULIRG). The star formation rate (SFR) of the host galaxy as derived from submillimeter and radio continuum emission is a few 100 M{sub sun} yr{sup -1}, which is an order of magnitude greater than the SFR derived from optical line emission. The large discrepancy between the SFRs derived from different observing wavelengths indicates the presence of a bulk of dust-obscured star formation and molecular gas that is enough to sustain the intense star formation. We failed to detect CO emission and derived 2{sigma} upper limits on the velocity-integrated CO (2-1) luminosity of L'{sub CO} < 6.9 x 10{sup 9} K km s{sup -1} pc{sup 2} and the molecular gas mass of M{sub H{sub 2}}< 5.5x10{sup 9} M{sub sun} by adopting a velocity width of 300 km s{sup -1} and a CO-to-H{sub 2} conversion factor of {alpha}{sub CO} = 0.8 M{sub sun} (K km s{sup -1} pc{sup 2}){sup -1}, which are standard values for ULIRGs. The lower limit on the ratio of far-infrared luminosity to CO luminosity, a measure of the star formation efficiency, is higher compared to that of other gamma-ray burst hosts and other galaxy populations, which is consistent with active star formation taking place in this galaxy.

• OSTI ID: 21582962
• Journal Information: Astrophysical Journal, Vol. 738, Issue 1; Other Information: DOI: 10.1088/0004-637X/738/1/33; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
CARBON MONOXIDE
COSMIC GAMMA BURSTS
EMISSION
GALAXIES
LUMINOSITY
STARS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
COSMIC RADIATION
IONIZING RADIATIONS
OPTICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PRIMARY COSMIC RADIATION
RADIATIONS