IAUS379: Dynamical Masses of Local Group Galaxies

One particularly promising way to understand the nature of dark matter is to study the so-called core-cusp problem. Many solutions have been investigated to solve it and one possibility is that the nature of the dark matter itself is different from the successful $\Lambda$-Cold Dark Matter model. To reduce the impact of baryonic physics which obscures our ability to constrain dark matter, we need to study the most dark matter dominated systems known, ultra-faint dwarfs.
Here we present the first spectroscopic observations of the Antlia B, a distant (d ∼ 1.35 Mpc) ultra-faint dwarf ($M_V = -9.4$, M$_\star ∼ 8\times 10^5$M$_\odot$ ), from MUSE-Faint – a survey of ultra-faint dwarfs with the Multi Unit Spectroscopic Explorer. We measure line-of-sight velocities of 127 member stars, and combine these with GravSphere, a Jeans modelling code, to place constraints on dark matter and derive the first dark matter density profile for this object.
In particular we present constraints on the nature of self-interacting dark matter (SIDM) that is based on the assumption that the dark matter particles can scatter with one another, being able to transport heat through the dark matter halo, altering the halo structure – and, possibly, producing a constant-density core in the heart of the halo; and scalar field dark matter (SFDM) that is a Bose-Einstein condensate and a quantum superfluid and can suppress structure formation when there is a strong repulsive self-interaction. These are to our knowledge the first constraints on SFDM using ultra-faint dwarf galaxies and we show that we can rule out SFDM as an explanation for the cores in the larger dwarf galaxies in the Local Group. We also show that if Antlia B has a core produced by SFDM, the characteristic length scale of the repulsive self-interaction has to be smaller than $R_{\text{TF}} \approx 0.37$ kpc.