Hubble space telescope and spitzer observations of the afterglow and host galaxy of GRB 050904 at z = 6.295

E. Berger, R. Chary, L. L. Cowie, P. A. Price, B. P. Schmidt, D. B. Fox, S. B. Cenko, S. G. Djorgovski, A. M. Soderberg, S. R. Kulkarni, P. J. Mccarthy, M. D. Gladders, B. A. Peterson, A. J. Barger

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27 Scopus citations


We present deep Hubble Space Telescope (HST) and Spitzer Space Telescope observations of GRB 050904 at z = 6.295. We detect the afterglow in the H band more than 3 weeks after the burst and confirm the presence of a jet break at t ≈ 2.1 days. This leads to an estimated opening angle of about 4° and a beaming-corrected energy of about 1051 ergs, similar to those of lower redshift gamma-ray bursts (GRBs). We do not detect an underlying host galaxy with either HST or Spitzer. From the upper limits we infer an extinction-corrected absolute magnitude MUV ≳ -20.3 mag, or L ≲ L*, a star formation rate of ≲5.7 M yr -1, and a stellar mass of ≲ few × 109 M . A comparison to spectroscopically confirmed galaxies at z > 5.5 reveals that the host of GRB 050904 is fainter and has a lower star formation rate than at least 80% of these objects. Finally, using our luminosity limits, and the metallicity of about 0.05 Z inferred from the afterglow absorption spectrum, we place the first limit on the luminosity-metallicity relation at z > 6. Future afterglow and host galaxy observations of z ≳ 4 GRBs should elucidate whether the mass- and luminosity-metallicity relations continue to evolve beyond the present limits of z ≲ 2.

Original languageEnglish (US)
Pages (from-to)102-106
Number of pages5
JournalAstrophysical Journal
Issue number1 PART 1
StatePublished - Aug 10 2007

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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