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

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    28 Citations (Scopus)


    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
    Pages (from-to)102-106
    Number of pages5
    JournalAstrophysical Journal
    Issue number1 PART 1
    Publication statusPublished - 10 Aug 2007


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