2019/01/31 by Andreas Burkert, Duncan Forbes · 1 citation
Physics and Astronomy · #astro-ph.GA
paper · pdf · doi:10.3847/1538-3881/ab5b0e
11 pages, 4 figures, ApJ in press
arxiv created 2019/11/27 · arxiv updated 2020/01/29
We confirm that the number of globular clusters (GCs), NGC, is an excellent tracer of their host galaxy's halo virial mass Mvir. The simple linear relation Mvir = 5 × 109 M\odot × NGC fits the data perfectly from Mvir = 1010 M\odot to Mvir = 2 × 1015 M\odot. This result is independent of galaxy morphology and extends statistically into the dwarf galaxy regime with Mvir = 108 - 1010 M\odot, including the extreme ultra diffuse galaxy DF44. As this correlation does not depend on GC mass it is ideally suited for high-precision determinations of Mvir. The linearity is most simply explained by cosmological merging of a high-redshift halo seed population that hosted on average one GC per 5 × 108 M\odot of dark matter. We show that hierarchical merging is also extremely powerful in restoring a linear correlation and erasing signatures of even a strong secular evolution of GC systems. The cosmological merging scenario also implies a strong decline of the scatter in NGC with increasing virial mass δNGC/NGC ∼ Mvir-1/2 in contrast with the observations that show a roughly constant scatter, independent of virial mass. This discrepancy can be explained if errors in determining virial masses from kinematical tracers and gravitational lensing are on the order of a factor of 2. GCs in dwarf satellite galaxies pose a serious problem for high-redshift GC formation scenarios; the dark halo masses of dwarf galaxies hosting GCs therefore might need to be an order of magnitude larger than currently estimated.