Modelling H I distribution and kinematics in the edge-on dwarf irregular galaxy KK250

We model the observed vertical distribution of the neutral hydrogen (H I) in the faint (M_B ∼ -13.7 mag) edge-on dwarf irregular galaxy KK250. Our model assumes that the galaxy consists of axisymmetric, coplanar gas and stellar discs in the external force-field of a spherical dark matter halo, and in vertical hydrostatic equilibrium. The velocity dispersion of the gas is left as a free parameter in the model. Our best-fitting model is able to reproduce the observed vertical distribution of the H I gas, as well as the observed velocity profiles. The best-fitting model has a large velocity dispersion (∼22 km s^-1) at the centre of the galaxy, which falls to a value of ∼8 km s^-1 by a galactocentric radius of 1 kpc, which is similar to both the scalelength of the stellar disc, as well as the angular resolution of the data along the radial direction. Similarly, we find that the thickness of the H I disc is also minimum at ∼1 kpc, and increases by about a factor of ∼2 as one goes to the centre of the galaxy or out to ∼3 kpc. The minimum intrinsic half-width at half-maximum (HWHM) of the H I vertical distribution in KK250 is ∼350 pc. For comparison the HWHM of the vertical distribution of the H I in the solar neighbourhood is ∼70-140 pc. Our results are hence consistent with other observations which indicate that dwarf galaxies have significantly puffier gas discs than spirals.