The number of globular clusters around the iconic UDG DF44 is as expected for dwarf galaxies

Teymoor Saifollahi; Ignacio Trujillo; Michael A. Beasley; Reynier F. Peletier; Johan H. Knapen

doi:10.1093/mnras/staa3016

paper

The number of globular clusters around the iconic UDG DF44 is as expected for dwarf galaxies

arXiv:2006.14630 · doi:10.1093/mnras/staa3016

Abstract

There is a growing consensus that the vast majority of ultra-diffuse galaxies (UDGs) are dwarf galaxies. However, there remain a few UDGs that seem to be special in terms of their globular cluster (GC) systems. In particular, according to some authors, certain UDGs exhibit large GC populations when compared to expectations from their stellar (or total) mass. Among these special UDGs, DF44 in the Coma cluster is one of the better-known examples. DF44 has been claimed to have a relatively high number of GCs, $N_{GC} = 7 4_{- 18}^{+ 18}$ , for a stellar mass of only $3 \times 1 0^{8}$ $M_{⊙}$ which would indicate a much larger dark halo mass than dwarfs of similar stellar mass. In this paper we revisit this number and, contrary to previous results, find $N_{GC} = 2 1_{- 9}^{+ 7}$ assuming that the distribution of the GCs follows the same geometry as the galaxy. If we assume that the GCs around DF44 are distributed in a (projected) circularly symmetric way and, if we use a less strict criterion for the selection of the GCs, we find $N_{GC} = 1 8_{- 12}^{+ 23}$ . Making use of the $M_{GC} - M_{halo}$ relation, this number of GCs suggests a dark matter halo mass of $M_{ha l o} = 1. 1_{- 0.5}^{+ 0.4} \times 1 0^{11} M_{⊙}$ , a value which is consistent with the expected total mass for DF44 based on its velocity dispersion, $σ = 3 3_{- 3}^{+ 3}$ km s $^{- 1}$ . We conclude that the number of GCs around DF44 is as expected for regular dwarf galaxies of similar stellar mass and DF44 is not extraordinary in this respect.

arXiv comment16 pages, 13 figures, accepted for publication in MNRAS, minor changes on the text to match the accepted version

The number of globular clusters around the iconic UDG DF44 is as expected for dwarf galaxies

Abstract

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