ASTRO-H White Paper - Chemical Evolution in High-z Universe

TL;DR

This paper discusses ASTRO-H's potential to study chemical evolution in the high-redshift universe by observing X-ray afterglows of GRBs and Blazars, enabling detection of heavy elements and the warm-hot intergalactic medium.

Contribution

It demonstrates ASTRO-H's capability to measure chemical evolution and the properties of the IGM at high redshift using X-ray spectroscopy of transient sources.

Findings

Detection of heavy element features in high-z sources

Constraints on the warm-hot intergalactic medium (WHIM)

First measurements of temporal spectral behavior of GRB afterglows and Blazars

Abstract

In this paper, we demonstrate ASTRO-H's capability to measure the chemical evolution in the high-z (z <~ 3) universe by observing X-ray afterglows of gamma-ray bursts (GRBs) and distant Blazars. Utilizing these sources as background light sources, the excellent energy resolution of ASTRO-H/SXS allows us to detect emission and absorption features from heavy elements in the circumstellar material in the host galaxies, from the intergalactic medium (IGM) and in the ejecta of GRB explosions. In particular, we can constrain the existence of the warm-hot intergalactic material (WHIM), thought to contain most of the baryons at redshift of z < ~3, with a typical exposure of one day for a follow-up observation of a GRB afterglow or 300 ks exposure for several distant Blazars. In addition to the chemical evolution study, the combination of the SGD, HXI, SXI and SXS will measure, for the first time, the temporal behavior of the spectral continuum of GRB afterglows and Blazars over a broad energy range and short time scales allowing detailed modeling of jets. The ability to obtain these data from GRB afterglows will depend critically on the availability of GRB triggers and the capability of ASTRO-H to respond rapidly to targets of opportunity. At the present time it seems as if Swift will still be functioning normally during the first two years of ASTRO-H operations providing the needed triggering capability.