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Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2017

Solving the conundrum of intervening strong Mg II absorbers towards gamma-ray bursts and quasars

L. Christensen
  • Fonction : Auteur
N. Annau
  • Fonction : Auteur
J. Selsing
  • Fonction : Auteur
J. Fynbo
A. de Ugarte Postigo
R. Cañameras
D. Passi
  • Fonction : Auteur
P. Cortés-Zuleta
  • Fonction : Auteur
L. Ellison
  • Fonction : Auteur
V. D’odorico
  • Fonction : Auteur
G. Becker
  • Fonction : Auteur
A. Berg
  • Fonction : Auteur
Z. Cano
  • Fonction : Auteur
S. Covino
G. Cupani
  • Fonction : Auteur
V. D’elia
  • Fonction : Auteur
  • PersonId : 973564
K. Heintz
  • Fonction : Auteur

Résumé

Previous studies have shown that the incidence rate of intervening strong Mg ii absorbers towards gamma-ray bursts (GRBs) were a factor of 2–4 higher than towards quasars. Exploring the similar sized and uniformly selected legacy data sets XQ-100 and XSGRB, each consisting of 100 quasar and 81 GRB afterglow spectra obtained with a single instrument (VLT/X-shooter), we demonstrate that there is no disagreement in the number density of strong Mg ii absorbers with rest-frame equivalent widths \hbox{$W_{\rm r}^{\lambda2796}>1$} Å towardsGRBs and quasars in the redshift range 0.1 ≲ z ≲ 5. With large and similar sample sizes, and path length coverages of Δz = 57.8 and 254.4 for GRBs and quasars, respectively, the incidences of intervening absorbers are consistent within 1σ uncertainty levels at all redshifts. For absorbers at z < 2.3, the incidence towards GRBs is a factor of 1.5 ± 0.4 higher than the expected number of strong Mg ii absorbers in Sloan Digital Sky Survey (SDSS) quasar spectra, while for quasar absorbers observed with X-shooter we find an excess factor of 1.4 ± 0.2 relative to SDSS quasars. Conversely, the incidence rates agree at all redshifts with reported high-spectral-resolution quasar data, and no excess is found. The only remaining discrepancy in incidences is between SDSS Mg ii catalogues and high-spectral-resolution studies. The rest-frame equivalent-width distribution also agrees to within 1σ uncertainty levels between the GRB and quasar samples. Intervening strong Mg ii absorbers towards GRBs are therefore neither unusually frequent, nor unusually strong.
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Dates et versions

hal-02268008 , version 1 (13-10-2020)

Identifiants

Citer

L. Christensen, S. D. Vergani, S. Schulze, N. Annau, J. Selsing, et al.. Solving the conundrum of intervening strong Mg II absorbers towards gamma-ray bursts and quasars. Astronomy and Astrophysics - A&A, 2017, 608, pp.A84. ⟨10.1051/0004-6361/201731382⟩. ⟨hal-02268008⟩
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