Volume 419, Number 3, June I 2004
|Page(s)||927 - 940|
|Published online||07 May 2004|
The host of GRB 030323 at : A very high column density DLA system with a low metallicity *
European Southern Observatory, Alonso de Córdova 3107, Casilla 19001, Santiago 19, Chile
2 P. Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
3 Astronomical Institute “Anton Pannekoek”, University of Amsterdam & Center for High Energy Astrophysics, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
4 Department of Physics and Astronomy, Århus University, Ny Munkegade, 8000 Århus C, Denmark
5 Niels Bohr Institute, Astronomical Observatory, Copenhagen University, Juliane Mariesvej 30, 2100 København Ø, Denmark
6 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
7 Universities Space Research Association / US Naval Observatory Flagstaff Station, PO Box 1149, Flagstaff AZ 86002-1149, USA
8 Physics Department, University of Rome “Tor Vergata", Via della Ricerca Scientifica 1, 00133 Rome, Italy
9 Department of Physical Sciences, University of Hertfordshire, College Lane, Hatfield, Herts AL10 9AB, UK
10 Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
11 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218-2463, USA
12 Instituto de Astrofísica de Andalucía (IAA-CSIC), Apartado de Correos, 3004, 18080 Granada, Spain
13 NSSTC, SD-50, 320 Sparkman Dr., Huntsville, AL 35805, USA
14 Istituto di Astrofisica Spaziale e Fisica Cosmica – Sezione di Bologna, CNR, via Gobetti 101, 40129 Bologna, Italy
15 INAF – Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 34131 Trieste, Italy
16 Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand
17 Joint Astronomy Centre, 660 N, A'ohoku Place, Hilo, Hawaii, HI 96720, USA
18 Department of Physics & Astronomy, Clemson University, Clemson, SC 29634-0978, USA
Corresponding author: P. M. Vreeswijk, firstname.lastname@example.org
Accepted: 27 February 2004
We present photometry and spectroscopy of the afterglow of GRB 030323. VLT spectra of the afterglow show damped Lyα (DLA) absorption and low- and high-ionization lines at a redshift . The inferred neutral hydrogen column density, , is larger than any (GRB- or QSO-) DLA column density inferred directly from Lyα in absorption. From the afterglow photometry, we derive a conservative upper limit to the host-galaxy extinction: mag. The iron abundance is , while the metallicity of the gas as measured from sulphur is . We derive an upper limit on the H2 molecular fraction of . In the Lyα trough, a Lyα emission line is detected, which corresponds to a star-formation rate (not corrected for dust extinction) of roughly 1 M yr-1. All these results are consistent with the host galaxy of GRB 030323 consisting of a low metallicity gas with a low dust content. We detect fine-structure lines of silicon, *, which have never been clearly detected in QSO-DLAs; this suggests that these lines are produced in the vicinity of the GRB explosion site. Under the assumption that these fine-structure levels are populated by particle collisions, we estimate the volume density to be cm-3. HST/ACS imaging 4 months after the burst shows an extended mag object at a distance of 014 (1 kpc) from the early afterglow location, which presumably is the host galaxy of GRB 030323.
Key words: gamma rays: bursts / galaxies: distances and redshifts / galaxies: quasars: absorption lines / ISM: dust, extinction
© ESO, 2004
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