Star-formation rates of two GRB host galaxies at z ∼ 2 and a [C ii] deficit observed with ALMA
-
- Tetsuya Hashimoto
- Institute of Astronomy, National Tsing Hua University, 101, Section 2, Kuang-Fu Road, Hsinchu, 30013, Taiwan
-
- Bunyo Hatsukade
- Institute of Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan
-
- Tomotsugu Goto
- Institute of Astronomy, National Tsing Hua University, 101, Section 2, Kuang-Fu Road, Hsinchu, 30013, Taiwan
-
- Seong Jin Kim
- Institute of Astronomy, National Tsing Hua University, 101, Section 2, Kuang-Fu Road, Hsinchu, 30013, Taiwan
-
- Kouji Ohta
- Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto, Kyoto 606-8502, Japan
-
- Tohru Nagao
- Research Center for Space and Cosmic Evolution, Ehime University, Matsuyama, Ehime 790-8577, Japan
-
- Albert K H Kong
- Institute of Astronomy, National Tsing Hua University, 101, Section 2, Kuang-Fu Road, Hsinchu, 30013, Taiwan
-
- Kouichiro Nakanishi
- National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
-
- Jirong Mao
- Yunnan Observatories, Chinese Academy of Sciences, 650011 Kunming, Yunnan Province, China
Description
<jats:title>ABSTRACT</jats:title> <jats:p>The event rate of long gamma-ray bursts (GRBs) is expected to be a useful tracer of cosmic star-formation history. For this purpose, it is necessary to understand what kinds of star formation/galaxies are traced by GRBs. Here we report rest-frame far-infrared (FIR) continuum detections of the GRB 070521 and 080207 host galaxies at z ∼ 2 with Atacama Large Millimeter/submillimeter Array (ALMA) bands 8 and 9. FIR photometry provides reliable star-formation rates (SFRs), because FIR emission is free from dust extinction and possible radio contamination from the long-lived afterglows of GRBs. Spectral energy distribution fitting yields 49.85$^{+72.33}_{-2.86}$ and 123.4$^{+25.19}_{-21.78}$ M⊙ yr−1 for the 070521 and 080207 hosts, respectively. The derived SFRs place them on the ‘main sequence’ of normal star-forming galaxies at z ∼ 2. The derived SFRs are significantly lower than those from radio observations. It is inferred that the observed radio fluxes in a previous study are contaminated by afterglows. ALMA marginally detected the [C ii] 158-μm emission line from the GRB 080207 host galaxy with signal-to-noise ratio (S/N) ∼ 4. This is the first detection of [C ii] 158-μm from a GRB host at z > 2 and the second detection among known GRBs. The luminosity ratio of [C ii] 158 μm to FIR is 7.5 × 10−4, which is one of the smallest values among galaxies at z ∼ 1–2 with the same FIR luminosity. The ‘[C ii] deficit’ could be a new physical property with which to characterize GRB hosts at z ∼ 1–2. Possible parameters controlling the deficit include the metallicity, initial mass function and gas density.</jats:p>
Journal
-
- Monthly Notices of the Royal Astronomical Society
-
Monthly Notices of the Royal Astronomical Society 488 (4), 5029-5041, 2019-08-14
Oxford University Press (OUP)
- Tweet
Details 詳細情報について
-
- CRID
- 1360849944528845824
-
- ISSN
- 13652966
- 00358711
-
- Data Source
-
- Crossref
- KAKEN