We determine the intrinsic axial ratio distribution of the gas discs of extremely faint M _ { B } > -14.5 dwarf irregular galaxies .
We start with the measured ( beam corrected ) distribution of apparent axial ratios in the HI 21cm images of dwarf irregular galaxies observed as part of the Faint Irregular Galaxy GMRT Survey ( FIGGS ) .
Assuming that the discs can be approximated as oblate spheroids , the intrinsic axial ratio distribution can be obtained from the observed apparent axial ratio distribution .
We use a couple of methods to do this , and our final results are based on using Lucy ’ s deconvolution algorithm .
This method is constrained to produce physically plausible distributions , and also has the added advantage of allowing for observational errors to be accounted for .
While one might a priori expect that gas discs would be thin ( because collisions between gas clouds would cause them to quickly settle down to a thin disc ) , we find that the HI discs of faint dwarf irregulars are quite thick , with mean axial ratio < q > \sim 0.6 .
While this is substantially larger than the typical value of \sim 0.2 for the stellar discs of large spiral galaxies , it is consistent with the much larger ratio of velocity dispersion to rotational velocity ( \sigma / v _ { c } ) in dwarf galaxy HI discs as compared to that in spiral galaxies .
Our findings have implications for studies of the mass distribution and the Tully - Fisher relation for faint dwarf irregular galaxies , where it is often assumed that the gas is in a thin disc .