TY - JOUR
T1 - THE OFFSET and HOST LIGHT DISTRIBUTIONS of LONG GAMMA-RAY BURSTS
T2 - A NEW VIEW from HST OBSERVATIONS of SWIFT BURSTS
AU - Blanchard, Peter K.
AU - Berger, Edo
AU - Fong, Wen Fai
N1 - Publisher Copyright:
© 2016. The American Astronomical Society. All rights reserved..
PY - 2016/2/1
Y1 - 2016/2/1
N2 - We present the results of an extensive Hubble Space Telescope imaging study of 105, mostly Swift, long-duration gamma-ray bursts (LGRBs) spanning , which were localized using relative astrometry from ground- and space-based afterglow observations. We measure the distribution of LGRB offsets from their host centers and their relation to the underlying host light distribution. We find that the host-normalized offsets of LGRBs are more centrally concentrated than expected for an exponential disk profile, = 0.63, and in particular they are more concentrated than the underlying surface brightness profiles of their host galaxies and more concentrated than supernovae. The fractional flux distribution, with a median of 0.78, indicates that LGRBs prefer some of the brightest locations in their host galaxies but are not as strongly correlated as previous studies indicated. Importantly, we find a clear correlation between offset and fractional flux, where bursts at offsets exclusively occur at fractional fluxes , while bursts at have a uniform fractional flux distribution. This indicates that the spatial correlation of LGRBs with bright star-forming regions seen in the full sample is dominated by the contribution from bursts at small offset and that LGRBs in the outer parts of galaxies show no preference for unusually bright regions. We conclude that LGRBs strongly prefer the bright, inner regions of their hosts, indicating that the star formation taking place there is more favorable for LGRB progenitor production. This indicates that environmental factors beyond metallicity, such as binary interactions or IMF differences, may operate in the central regions of LGRB hosts.
AB - We present the results of an extensive Hubble Space Telescope imaging study of 105, mostly Swift, long-duration gamma-ray bursts (LGRBs) spanning , which were localized using relative astrometry from ground- and space-based afterglow observations. We measure the distribution of LGRB offsets from their host centers and their relation to the underlying host light distribution. We find that the host-normalized offsets of LGRBs are more centrally concentrated than expected for an exponential disk profile, = 0.63, and in particular they are more concentrated than the underlying surface brightness profiles of their host galaxies and more concentrated than supernovae. The fractional flux distribution, with a median of 0.78, indicates that LGRBs prefer some of the brightest locations in their host galaxies but are not as strongly correlated as previous studies indicated. Importantly, we find a clear correlation between offset and fractional flux, where bursts at offsets exclusively occur at fractional fluxes , while bursts at have a uniform fractional flux distribution. This indicates that the spatial correlation of LGRBs with bright star-forming regions seen in the full sample is dominated by the contribution from bursts at small offset and that LGRBs in the outer parts of galaxies show no preference for unusually bright regions. We conclude that LGRBs strongly prefer the bright, inner regions of their hosts, indicating that the star formation taking place there is more favorable for LGRB progenitor production. This indicates that environmental factors beyond metallicity, such as binary interactions or IMF differences, may operate in the central regions of LGRB hosts.
KW - gamma-ray burst: general
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U2 - 10.3847/0004-637X/817/2/144
DO - 10.3847/0004-637X/817/2/144
M3 - Article
AN - SCOPUS:84957998672
VL - 817
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2
M1 - 144
ER -