Infrared and Optical Observations of GRB 030115 and its ExtremelyRed Host Galaxy: Implications for Dark Bursts
We present near-infrared (NIR) and optical observations ofthe afterglow of GRB 030115. Discovered in aninfrared search at Kitt Peak5 hr after the burst trigger, this afterglow is the faintest everobserved in the R band at such an early epoch and exhibits very redcolors, with R-K~;6. The optical magnitude of the afterglow of GRB 030115is fainter than many upper limits for other bursts, suggesting thatwithout early NIR observations it would have been classified as a "dark"burst. Both the color and optical magnitude of the afterglow are likelydue to dust extinction atmoderate redshift z>2 and indicate that atleast some optical afterglows are very faint due to dust along the lineof sight.Multicolor Hubble Space Telescope observations were also takenof the host galaxy and the surrounding field. Photometric redshifts implythat the host and a substantial number of faint galaxies in the field areat z 2:5. The overdensity of galaxies is sufficiently great that GRB030115 may have occurred in a rich high-redshift cluster. The host galaxyshows extremely red colors (R-K = 5) and is the first GRB host to beclassified as an extremely red object (ERO). Some of the galaxiessurrounding the host also show very red colors, while the majority of theclusterare much bluer, indicating ongoing unobscured star formation. Asit is thought that much of high-redshift starformation occurs in highlyobscured environments, it may well be that GRB 030115 represents atransition object, between the relatively unobscured afterglows seen todate and a population of objects that are very heavily extinguished, evenin the NIR.
- Research Organization:
- COLLABORATION - NASA
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 927327
- Report Number(s):
- LBNL-63092; ASJOAB; R&D Project: KS0606; BnR: KA1401030; TRN: US0803180
- Journal Information:
- Astrophysical Journal, Vol. 647; Related Information: Journal Publication Date: 2006; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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