Absorption Selected Galaxies Along the Line of Sight to GRBs – Niels Bohr Institute - University of Copenhagen

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Absorption Selected Galaxies Along the Line of Sight to GRBs

Masters defence: Christina Henriksen , Niels Bohr Institute and Dark Cosmology Centre


The purpose of my thesis was to search for the galaxy counterpart of
strong MgII absorption systems seen in the spectra of GRBs. Previous
studies might have overlooked a whole population of faint galaxies at
small impact parameters for MgII absorption systems in QSOs because of its
bright glare. With the afterglows of GRBs fading a way, a clear sightline
makes deep spectroscopy at small impact parameters possible.
My work was on the three fields of GRB021004, GRB030226 and GRB020813 as
these both showed strong MgII absorption as well as had several candidates
for the absorbing galaxy within a small impact parameter. I used
spectroscopic data from FORS2 at the ESO VLT and I reduced
and calibrated the raw data as well as analyzed the combined science
frames. I was able to find galaxy counterparts in two absorption systems
based on [OII] emission, one in GRB021004 and one in GRB020813. Both of
the systems were at a small impact parameter, with the lowest for
the galaxy in GRB020813 of only 4.5” from the GRB and thus I have been
able to find possible absorbers at a small impact parameters.