Dust properties at z=6.3 in the host galaxy of GRB 050904

Abstract

We investigate the dust extinction properties in the host galaxy of the Gamma-Ray Burst (GRB) GRB 050904 at z=6.29 by analyzing simultaneous broad band observations of the optical and UV afterglow at three different epochs. We show that the peculiar afterglow spectral energy distribution (SED) observed at 0.5 days and at 1 day after the burst (1.6 and 3 hours rest frame) cannot be explained with dust reddening with any of the extinction curves observed at low redshift. Yet, the extinction curve recently inferred for the most distant BAL QSO at z=6.2 nicely reproduces the SED of GRB 050904 at both epochs. Our result provides an additional, independent indication that the properties of dust evolve beyond z~6. We discuss the implications of this finding within the context of the dust production mechanisms through the cosmic ages.

4 pages, 2 figures, accepted for publication in ApJL

References in corpus (4)

• Dust yields in clumpy SN shells: SN 1987A revisited
• No cold dust within the supernova remnant Cassiopeia A
• Far-infrared and sub-mm observations of the Crab nebula
• A metal rich molecular cloud surrounds GRB 050904 at redshift 6.3

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