McQuinn 2007 用伽玛暴探测再电离时期的IGM

主要内容:
不过要把IGM的吸收和DLA（damped laymann-alfa absorber）区分开来。

精彩摘抄:


文章信息:

arXiv:0710.1018 [ps, pdf, other]

Title: Probing the Neutral Fraction of the IGM with GRBs during the Epoch of Reionization

Authors: Matthew McQuinn, Adam Lidz, Matias Zaldarriaga, Lars Hernquist, Suvendra Dutta

Comments: 10 pages, 8 figures, submitted to MNRAS

Subjects: Astrophysics (astro-ph)

We show that near-infrared observations of the red side of the Ly-alpha line from a single gamma ray burst (GRB) afterglow cannot be used to constrain the global neutral fraction of the intergalactic medium (IGM), x_H, at the GRB's redshift to better than ~0.3, because some GRB sight-lines will encounter more neutral hydrogen than others owing to the patchiness of reionization. Consequently, GRBs during the epoch of reionization will often bear no discernible signature of a neutral IGM in their afterglow spectra. We discuss the constraints on x_H from the z = 6.3 burst, GRB050904, and quantify the probability of detecting a neutral IGM using future spectroscopic observations of high-redshift, near-infrared GRB afterglows. Assuming an observation with signal-to-noise similar to the Subaru FOCAS spectrum of GRB050904, that the column density distribution of damped Ly-alpha absorbers is the same as measured at lower redshifts, and that the redshift of the GRB is known, a GRB from an epoch when x_H = 0.5 can be used to detect a partly neutral IGM at 98% confidence level 5 - 10% of the time (and, for an observation with three times the sensitivity, 25-30% of the time).