Tejos 2009 伽玛暴余辉中的MgII吸收线

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貌似镁线比想像的强

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Title:		Casting light on the 'anomalous' statistics of Mg II toward Gamma-Ray Burst afterglows: the incidence of weak systems
Authors:		Tejos, Nicolas; Lopez, Sebastian; Prochaska, J. Xavier; Bloom, Joshua S.; Chen, Hsiao-Wen; Dessauges-Zavadsky, Miroslava; Maureira, Maria J.
Publication:		eprint arXiv:0905.3768
Publication Date:		05/2009
Origin:		ARXIV
Keywords:		Astrophysics - Cosmology and Extragalactic Astrophysics
Comment:		17 pages, 3 tables, 3 figures, submitted to the ApJ
Bibliographic Code:		2009arXiv0905.3768T

Abstract

We revisit echelle spectra (spectral resolution R ~ 40000) of 8 Gamma-Ray Burst afterglows to obtain the incidence (dN/dz) of weak intervening Mg II systems at a mean redshift of = 1.5. We show that dN/dz of systems having restframe equivalent widths 0.07 A <> 1 A, where dN/dz toward GRBs has been found to be larger than toward QSOs by a factor of ~ 4. We confirm the overdensity albeit at a factor of ~ 3 only. This suggests that any explanation for the GRB/QSO discrepancy, be it intrinsic to the absorbers or a selection effect, should be inherent only to the galaxies that host strong absorbers in the line-of-sight to GRBs. We argue that, of all scenarios that have been proposed, lensing amplification is the one that could explain the strong Mg II enhancement while allowing for no significant enhancement in the weak absorbers.

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