"Dark" GRB 080325 in a dusty massive galaxy at z ∼ 2

T. Hashimoto, K. Ohta, K. Aoki, I. Tanaka, K. Yabe, N. Kawai, W. Aoki, H. Furusawa, T. Hattori, M. Iye, K. S. Kawabata, N. Kobayashi, Y. Komiyama, G. Kosugi, Y. Minowa, Y. Mizumoto, Y. Niino, K. Nomoto, J. Noumaru, R. OgasawaraT. S. Pyo, T. Sakamoto, K. Sekiguchi, Y. Shirasaki, M. Suzuki, A. Tajitsu, T. Takata, T. Tamagawa, H. Terada, T. Totani, J. Watanabe, T. Yamada, A. Yoshida

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)

Abstract

We present optical and near-infrared observations of Swift GRB 080325 classified as a "dark gamma-ray burst (GRB)." Near-infrared observations with Subaru/MOIRCS provided a clear detection of afterglow in the Ks band, although no optical counterpart was reported. The flux ratio of rest-wavelength optical to X-ray bands of the afterglow indicates that the dust extinction along the line of sight to the afterglow is AV = 2.7-10 mag. This large extinction is probably the major reason for the optical faintness of GRB 080325. The J - Ks color of the host galaxy, (J - Ks = 1.3 in AB magnitude), is significantly redder than those for typical GRB hosts previously identified. In addition to J and Ks bands, optical images in B, Rc, I ′, and z ′ bands with Subaru/Suprime- Cam were obtained at about 1 year after the burst, and a photometric redshift of the host is estimated to be zphoto = 1.9. The host luminosity is comparable to L * at z ∼ 2 in contrast to the sub-L * property of typical GRB hosts at lower redshifts. The best-fit stellar population synthesis model for the host shows that the red nature of the host is attributed to a large dust extinction (AV = 0.8 mag), and that the host galaxy is massive (M * = 7.0 × 1010 M), which makes it one of the most massive GRB hosts yet identified. By assuming that the mass-metallicity relation for star-forming galaxies at z ∼ 2 is applicable for the GRB host, this large stellar mass suggests the high-metallicity environment around GRB 080325, consistent with inferred large extinction.

Original languageEnglish
Pages (from-to)378-384
Number of pages7
JournalAstrophysical Journal
Volume719
Issue number1
DOIs
Publication statusPublished - 2010 Aug 10

Keywords

  • Galaxies: photometry
  • Gamma rays: galaxies
  • Gamma-ray burst
  • Individual (GRB 080325)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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