EDP Sciences
Free access
Volume 409, Number 2, October II 2003
Page(s) L5 - L8
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20031237

A&A 409, L5-L8 (2003)
DOI: 10.1051/0004-6361:20031237


New search strategy for high z intervening absorbers: GRB 021004, a pilot study

P. M. Vreeswijk1, P. Møller2 and J. P. U. Fynbo3, 4

1  European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Santiago 19, Chile
2  European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748, Garching bei München, Germany
3  Department of Physics and Astronomy, Århus University, Ny Munkegade, 8000 Århus C, Denmark
4  Astronomical Observatory, Copenhagen University, Juliane Mariesvej 30, 2100 København K, Denmark

(Received 25 April 2003 / Accepted 6 August 2003)

We present near-infrared narrow- and broad-band imaging of the field of GRB 021004, performed with ISAAC on the UT1 of the ESO Very Large Telescope . The narrow-band filters were chosen to match prominent emission lines at the redshift of the absorption-line systems found against the early-time afterglow of GRB 021004: [ $\ion{O}{iii}$] at z=1.38 and H $\alpha$ at z=1.60, respectively. For the z=1.38 system we find an emission-line source at an impact parameter of 16 $^{\prime\prime}$, which is somewhat larger than the typical impact parameters of a sample of $\ion{Mg}{ii}$ absorbers at redshifts around unity. Assuming that this tentative redshift-identification is correct, the star formation rate of the galaxy is $13\pm2~M$ $_{\odot}$ yr -1. Our study reaches star-formation rate limits (5 $\sigma$) of 5.7  M $_{\odot}$ yr -1 at z=1.38, and 7.7  M $_{\odot}$ yr -1 at z=1.60. These limits correspond to a depth of roughly 0.13  L*. Any galaxy counterpart of the absorbers nearer to the line of sight either has to be fainter than this limit or not be an emission-line source.

Key words: gamma rays: bursts -- galaxies: distances and redshifts -- quasars: absorption lines

Offprint request: P. M. Vreeswijk, pvreeswi@eso.org

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