http://arxiv.org/abs/1602.04843
We explore the formation of massive high-redshift Population III (Pop III) galaxies through photoionization feedback. We consider dark matter halos formed from progenitors that have undergone no star formation as a result of early reionization and photoevaporation caused by a nearby galaxy. Once such a halo reaches $\sim 10^9 M_\odot$, corresponding to the Jeans mass of the photoheated intergalactic medium (IGM) at $z\approx 7$, pristine gas is able to collapse into the halo, potentially producing a massive Pop III starburst. We suggest that this scenario may explain the recent observation of strong He II $1640~ \AA ~$line emission in CR7, which is consistent with $\sim 10^7~M_\odot$ of young Pop III stars. Such a large mass of Pop III stars is unlikely without the photoionization feedback scenario, because star formation is expected to inject metals into halos above the atomic cooling threshold ($\sim 10^8~M_\odot$ at $z \approx 7$). We use merger trees to analytically estimate the abundance of observable Pop III galaxies formed through this channel, and find a number density of $\approx 10^{-6}~{\rm Mpc^{-3}}$ at $z=6.6$ (the redshift of CR7). This is comparable to the density of Ly$\alpha$ emitters as bright as CR7.
E. Visbal, Z. Haiman and G. Bryan
Wed, 17 Feb 16
17/55
Comments: 5 pages, 4 figures, submitted to MNRAS
You must be logged in to post a comment.