2017MNRAS.465L..49J

We assess the intrinsic thickness parameter, q_o, for a sample of dwarf irregular galaxies and compare to larger, more massive spiral galaxy systems. We use optical photometry to determine b/a (minor-to-major axial ratio), and we use the H I kinematic inclination angle to derive q_o. We find that q_o ranges from 0.1 to 0.8 for the dwarfs. We find a trend in q_o with luminosity, indicating that fainter dwarfs are thicker than brighter ones, similar to previous studies. However, we also find a trend in q_o with H I kinematic inclination, which indicates that either the radius at which we measure b/a may be too small, or, that the stellar and gas discs have different inclinations. Because we selected only those objects that have nearly identical morphological and kinematic position angles, we find the latter reason unlikely. We find a weak trend in q_o with h_z/R_D (ratio of stellar scaleheight to scalelength), which points to b/a not fully representing the stellar disc distribution. We conclude that a constant q_o may not be appropriate for dwarf irregulars.