Solving the conundrum of intervening strong Mg II absorbers towards gamma-ray bursts and quasars
Vergani, S. D.
Fynbo, J. P. U.
de Ugarte Postigo, A.
Ellison, S. L.
Berg, T. A. M.
Heintz, K. E.
Tanvir, N. R.
Thöne, C. C.
AffiliationUniv Arizona, Steward Observ, Dept Astron
MetadataShow full item record
PublisherEDP SCIENCES S A
CitationSolving the conundrum of intervening strong Mg II absorbers towards gamma-ray bursts and quasars 2017, 608:A84 Astronomy & Astrophysics
JournalAstronomy & Astrophysics
Rights© ESO, 2017
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at email@example.com.
AbstractPrevious 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 W-r(lambda 2796) > 1 angstrom towards GRBs and quasars in the redshift range 0.1 less than or similar to z less than or similar to 5. With large and similar sample sizes, and path length coverages of Delta z = 57.8 and 254 : 4 for GRBs and quasars, respectively, the incidences of intervening absorbers are consistent within 1 sigma 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 1 sigma uncertainty levels between the GRB and quasar samples. Intervening strong Mg II absorbers towards GRBs are therefore neither unusually frequent, nor unusually strong.
NoteOpen access journal.
VersionFinal published version
SponsorsYDUN [DFF 4090-00079]; French National Research Agency (ANR) [ANR-16-CE31-0003 BEaPro]; FONDECYT ; PFB-06 CATA; Ramon y Cajal fellowships; RSR a BBVA Foundation Grant for Researchers and Cultural Creators; Spanish Ministry of Economy and Competitiveness [AYA2014-58381-P]; National Science Foundation [AST-1615814]; Juan de la Cierva Incorporacion fellowship [IJCI-2014-21669]; Spanish research project [AYA2014-58381-P]; Project Grant from Icelandic Research Fund [162948-051]; NOVA; NWO-FAPESP grant for advanced instrumentation in astronomy; ASI (Italian Space Agency) [2015-046-R.0]; European Union Horizon Programme under the AHEAD project ; Danish Council for Independent Research [DFF 4002-00275]