Gamma ray bursts as probes of dust in the evolving universe

Dust is ubiquitous in the universe. Understanding where it comes from and where we observe it can have major implications to all astronomical observations. In this study, we investigate how gamma ray bursts (GRBs) can be used as probes of dust in the evolving universe. Making the simplification that silicate dust comes from core collapse supernovae and that graphite dust is produced in the winds of low- to intermediate-mass stars, we present numerical simulations of the resulting dust evolution in GRB hosts and show how the SEDs evolve. Dust extinction laws are re-derived from scattering theory of small particles and the dependence of the extinction laws on varying dust properties are explored. Finally, we compare the predictions of our simulations of dust evolution and our modeled extinction laws to 82 GRB SEDs spanning the last 13 years. We measure the column densities of graphite and silicate along the line of sight to these GRBs as well as the overall visual extinction AV in the co-moving frame and the dust-to-gas ratios. We find no clear evolutionary trend with respect to the AV values or the graphite-to-silicate ratio as a function of redshift. However, we do detect more silicate than graphite in nearly every burst, implying high production rates of silicate in core-collapse supernovae, and we discover a graphite component previously undetected in 14 GRBs in our sample. These results are examined in the context of our evolutionary models, and we discuss the implications for star formation in the early universe.