Looking for dark matter in HVCs/CHVCs: Leo-T a test case [GA]


Assuming a hydrostatic equilibrium condition in an \HI~cloud, we set up and solve the Poisson’s equation to calculate the observed \HI~structure. We construct an {\it iterative} method to estimate the intrinsic velocity dispersion profile (which is not a directly observable quantity) and solve the hydrostatic equilibrium equation. We further use this method to identify if a dark matter halo hosts an \HI~cloud or not. Our simulation shows that the presence of a low mass dark matter halo in an \HI~cloud can alter the hydrostatic equilibrium significantly such as to introduce an easily detectable change in the surface density profile. We apply our method to Leo-T, a suspected dark galaxy and found that it is hosted by a dark matter halo of mass $\sim 8.8 \times 10^6$ \ms. We also estimated the dark matter halo parameters of Leo-T by solving \HI~structure in a large number of pseudo-isothermal halos and comparing the resulting \HI~surface density profiles to the observed one. The dark matter halo parameters found to be $\rho_0 \simeq 0.25$ \mspcc~and $r_s \simeq 141$ parsec. Our analysis shows that the `mass’ of the dark matter halo primarily determines the \HI~distribution of a cloud under hydrostatic equilibrium. Our method could be used to identify potential dark galaxies from a population of Compact or Ultra Compact High Velocity Clouds.

Read this paper on arXiv…

N. Patra
Wed, 14 Feb 18

Comments: 12 pages, 11 figures, under review in MNRAS, comments are welcome