Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21714102l&link_type=abstract
American Astronomical Society, AAS Meeting #217, #141.02; Bulletin of the American Astronomical Society, Vol. 43, 2011
Astronomy and Astrophysics
Astronomy
Scientific paper
We present multi-band optical and near-infrared observations of 19 short γ-ray burst (GRB) host galaxies, aimed at measuring their stellar masses and population ages. The goals of this study are to evaluate whether short GRBs track the stellar mass distribution of galaxies, to investigate the progenitor delay time distribution, and to explore any connection between long and short GRB progenitors. Comparing the distribution of stellar masses found using a single-stellar population model to the general galaxy mass function, we find that short GRBs track the cosmic stellar mass distribution only if the late-type hosts generally have maximal masses. However, there is an apparent dearth of early-type short GRB hosts compared to the equal contribution of early- and late-type galaxies to the cosmic stellar mass budget. These results suggest that stellar mass may not be the sole parameter controlling the short GRB rate, and raise the possibility of a two-component model with both mass and star formation playing a role (reminiscent of the case for Type Ia supernovae). If short GRBs in late-type galaxies indeed track star formation activity, the resulting typical delay time is 0.2 Gyr, while those in early-type hosts have a typical delay of 3 Gyr. Using the same stellar population models to fit 22 long GRB host galaxies in a similar redshift range we find that they have significantly lower masses and younger population ages. Most importantly, the two GRB host populations remain distinct even if we consider only the star-forming hosts of short GRBs, supporting our previous findings (based on star formation rates and metallicities) that the progenitors of long GRBs and short GRBs in late-type galaxies are distinct.
This work was partially supported by Swift AO5 grant #5080010 and AO6 grant #6090612. Additional support was provided by the Harvard College Research Program.
Berger Edmond
Leibler Camille N.
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