摘要：Context. As a result of their relation to massive stars, long-duration
gamma-ray bursts (GRBs) allow the pinpointing of star formation in galaxies independent of
redshift, dust obscuration, or galaxy mass/size, thus providing a unique tool to
investigate star formation history over cosmic time.
Aims. About half of the optical afterglows of long-duration GRBs are
missed owing to dust extinction and are primarily located in the most massive GRB hosts.
It is important to investigate the amount of obscured star formation in these GRB host
galaxies to understand this bias.
Methods. Radio emission of galaxies correlates with star formation, but
does not suffer extinction as do the optical star formation estimators. We selected 11 GRB
host galaxies with either large stellar mass or large UV-based and optical-based star
formation rates (SFRs) and obtained radio observations of these with the Australia
Telescope Compact Array and the Karl Jansky Very Large Array.
Results. Despite intentionally selecting GRB hosts with expected high
SFRs, we do not find any radio emission related to star formation in any of our targets.
Our upper limit for GRB 100621A implies that the earlier reported radio detection was due
to afterglow emission. We detect radio emission from the position of GRB 020819B, but
argue that it is in large part, if not completely, due to afterglow contamination.
Conclusions. Half of our sample has radio-derived SFR limits, which are
only a factor 2–3 above the optically measured SFRs. This supports other recent studies
that the majority of star formation in GRB hosts is not obscured by dust.
关键词：galaxies: star formation;radio continuum: galaxies;gamma-ray burst: general
