The First Billion Years project: gamma-ray bursts at z > 5

Abstract

Long gamma-ray burst's (LGRB's) association to the death of massive stars suggest they could be used to probe the cosmic star formation history (CSFH) with high accuracy, due to their high luminosities. We utilise cosmological simulations from the First Billion Years project to investigate the biases between the CSFH and the LGRB rate at z > 5, assuming various different models and constraints on the progenitors of LGRBs. We populate LGRBs using a selection based on environmental properties and demonstrate that the LGRB rate should trace the CSFH to high redshifts. The measured LGRB rate suggests that LGRBs have opening angles of θ jet = 0.1 • , although the degeneracy with the progenitor model cannot rule out an underlying bias. We demonstrate that proxies that relate the LGRB rate with global LGRB host properties do not reflect the underlying LGRB environment, and are in fact a result of the host galaxy's spatial properties, such that LGRBs can exist in galaxies of solar metallicity. However, we find a class of host galaxies that have low stellar mass and are metal-rich, and that their metallicity dispersions would not allow low-metallicity environments. Detection of hosts with this set of properties would directly reflect the progenitor's environment. We predict that 10% of LGRBs per year are associated with this set of galaxies that would have forbidden line emission that could be detected by instruments on the James Webb Space Telescope. Such a discovery would place strong constraints on the collapsar model and suggest other avenues to be investigated.

Growth of First Galaxies: Impacts of Star Formation and Stellar Feedback

“…This code was extended and modified to include the treatment of population III (Pop III) star formation, Lyman-Werner feedback, non-equilibrium primordial chemistry, and dust formation/destruction in the First Billion Year (FiBY) project (e.g., Khochfar & Dalla Vecchia et al in prep.). The impacts of these new physical processes on galaxy formation have been studied in a series of papers of the FiBY project (e.g., Johnson et al 2013;Paardekooper et al 2013;Agarwal & Khochfar 2015;Elliott et al 2015). In this work, we do not consider the formation of Pop III stars and non-equilibrium primordial chemistry, because our focus are more massive galaxies after the era of first mini-halos.…”

AN UNEXPECTEDLY LOW-REDSHIFT EXCESS OF SWIFT GAMMA-RAY BURST RATE

“…Observations also show that some long GRBs are associated with the deaths of massive stars which will create core collapse SNe (Hjorth et al 2003;Stanek et al 2003). Therefore, GRBs can be used to investigate the SFR at high redshifts (Totani 1997;Wijers et al 1998;Lamb & Reichart 2000;Porciani & Madau 2001;Broom & Loeb 2002;Lin et al 2004;Wang & Dai 2009;Kistler et al 2009;Wanderman & Piran 2010;Butler et al 2010;Elliott et al 2012Elliott et al , 2014. In order to measure SFR using GRBs, the relation between the rate of GRBs and the SFR should be known.…”

Constraining the PopIII IMF with high-zGRBs

“…Some of them are so bright that they have been observed up to extremely high redshift (Salvaterra et al 2009;Tanvir et al 2009;Cucchiara et al 2011). In fact, different models (Bromm & Loeb 2002;Salvaterra & Chincarini 2007;de Souza et al 2011;Salvaterra et al 2012;Ghirlanda et al 2015;Elliott et al 2015) consistently predict that ∼ 3% of the GRBs detected by the Swift satellite should lie at z > 6. Among these, some might also be GRBs from the earliest generation (PopIII) of stars (Suwa & Ioka 2011;Toma et al 2011;Maio & Barkov 2014).…”