HI and Mass Distribution of GR8

Abstract

AbstractThe dwarf irregular galaxy GR8, which is at the extreme faint end of the luminosity and mass functions, is studied using optical photometry and 21cm HI line observations. It is shown that rotation is only important to the gravitational support of the system in the inner parts (r < 250 pc). GR8 is one of the very few non-elliptical systems known (with M81dwA) where the random motions provide essentially all the support in the outer parts (r ≥ 500 pc). The Gaussian nature of the HI distribution and the isothermal distribution of the HI velocity dispersion implies M α R3 in the outer regions of GR8 (ie the stellar disk and the HI lie in the approximately uniform density core of the dark halo).