VLT/X-Shooter spectroscopy of the afterglow of the Swift GRB 130606A: Chemical abundances and reionisation at z ~ 6

The reionisation of the Universe is a process that is thought to have ended around z ~ 6, as inferred from spectroscopy of distant bright background sources, such as quasars (QSO) and gamma-ray burst (GRB) after glows. We aim to measure the degree of ionisation of the intergalactic medium (1GM) betw...

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Bibliographic Details
Published in:Astronomy and astrophysics (Berlin) 2015-08, Vol.580, p.A139
Main Authors: Hartoog, O E, Malesani, D, Fynbo, J P U, Goto, T, Kruhler, T, Vreeswijk, P M, De Cia, A, Xu, D, Moller, P, Covino, S
Format: Article
Language:English
Subjects:
Afterglows
Astrophysics
Continuums
Cosmology and Extra-Galactic Astrophysics
Galactic Astrophysics
Gamma ray bursts
Physics
Quasars
Samples
Spectroscopy
Statistical methods
Universe
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Summary:The reionisation of the Universe is a process that is thought to have ended around z ~ 6, as inferred from spectroscopy of distant bright background sources, such as quasars (QSO) and gamma-ray burst (GRB) after glows. We aim to measure the degree of ionisation of the intergalactic medium (1GM) between z = 5.02-5.84 and to study the chemical abundance pattern and dust content of its host galaxy. We estimated the UV continuum of the GRB afterglow using a power-law extrapolation, then measured the flux decrement due to absorption at Ly[alpha], [beta], and [gamma] wavelength regions. Our measurements confirm that the Universe is already predominantly ionised over the redshift range probed in this work, but was slightly more neutral at z [>] 5.6. GRBs are useful probes of the ionisation state of the 1GM in the early Universe, but because of internal scatter we need a larger statistical sample to draw robust conclusions.
ISSN:0004-6361
1432-0746
1432-0756
DOI:10.1051/0004-6361/201425001