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 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.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/626409 |
| Date | 11 December 2017 |
| Creators | Christensen, L., Vergani, S. D., Schulze, S., Annau, N., Selsing, J., Fynbo, J. P. U., de Ugarte Postigo, A., Cañameras, R., Lopez, S., Passi, D., Cortés-Zuleta, P., Ellison, S. L., D’Odorico, V., Becker, G., Berg, T. A. M., Cano, Z., Covino, S., Cupani, G., D’Elia, V., Goldoni, P., Gomboc, A., Hammer, F., Heintz, K. E., Jakobsson, P., Japelj, J., Kaper, L., Malesani, D., Møller, P., Petitjean, P., Pugliese, V., Sánchez-Ramírez, R., Tanvir, N. R., Thöne, C. C., Vestergaard, M., Wiersema, K., Worseck, G. |
| Contributors | Univ Arizona, Steward Observ, Dept Astron |
| Publisher | EDP SCIENCES S A |
| Source Sets | University of Arizona |
| Language | English |
| Detected Language | English |
| Type | Article |
| Rights | © ESO, 2017 |
| Relation | http://www.aanda.org/10.1051/0004-6361/201731382 |
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