http://arxiv.org/abs/1910.09924
We explore a suite of high-resolution cosmological simulations from the First Billion Years (FiBY) project at $z \geq 6$ to identify low-mass stellar systems, with a particular focus on globular clusters (GCs). Within the demographics of substructures found in the simulations, two distinct groups of objects emerge. We associate the first group, which appear to have a high baryon fraction ($f_{\rm{b}} \geq 0.95$), with infant GC candidates. The second group exhibit a high stellar fraction ($f_* \geq 0.95$) and show a resemblance to ultra-faint dwarf galaxies. The infant GC candidates are characterised by a stellar content similar to the one observed in present-day GCs, but they still contain a high gas fraction ($f_{\rm{gas}} \sim 0.95$) and a relatively low amount of dark matter. They are very compact systems, with high stellar mass densities and sizes which are consistent with recent estimates based on the first observations of possible proto-GCs at high redshifts. Such infant GCs appear to be more massive and more abundant in massive host galaxies, indicating that the assembly of galaxies via mergers may play an important role in shaping up several GC-host scaling relations. Specifically, we express the relation between the mass of the most massive infant GC and its host stellar mass as $\log (M_{\rm cl}) = (0.31\pm0.15)\log (M_{\rm *,gal}) + (4.17\pm1.06)$. Finally, we assess that the present-day GC mass — halo mass relation offers a satisfactory description of the behaviour of our infant GC candidates at high redshift, suggesting that such a relation may be set at formation.
F. Phipps, S. Khochfar, A. Varri, et. al.
Wed, 23 Oct 19
31/64
Comments: 15 pages, 8 figures, submitted to MNRAS