We present an analysis of the sky distribution of neutral hydrogen (HI)deficiency and spectral asymmetry for galaxies detected by the HI ParkesAll-Sky Survey (HIPASS) as a function of projected environment density.Previous studies of galaxy HI deficiency using HIPASS were sensitive togalaxies that are extremely HI rich or poor. We use an updated binningstatistic for measuring the global sky distribution of HI deficiency that issensitive to the average deficiencies. Our analysis confirms the result fromprevious studies that galaxies residing in denser environments, such as Virgo,are on average more HI deficient than galaxies at lower densities. However,many other individual groups and clusters are not found to be on averagesignificantly HI poor, in contradiction to previous work. In terms of HIspectral asymmetries, we do not recover any significant trend of increasingasymmetry with environment density as found for other galaxy samples. We alsoinvestigate the correlation between HI asymmetry and deficiency, but find novariation in the mean asymmetry of galaxies that are HI rich, normal or poor.This indicates that there is either no dependence of asymmetry on HIdeficiency, or a galaxy's HI deficiency only has a small influence on themeasured HI asymmetry that we are unable to observe using only integratedspectra.

The mass-to-light ratio (M/L) is a key parameter in decomposing galacticrotation curves into contributions from the baryonic components and the darkhalo of a galaxy. One direct observational method to determine the disc M/L isby calculating the surface mass density of the disc from the stellar verticalvelocity dispersion and the scale height of the disc. Usually, the scale heightis obtained from near-IR studies of edge-on galaxies and pertains to the older,kinematically hotter stars in the disc, while the vertical velocity dispersionof stars is measured in the optical band and refers to stars of all ages (up to~10 Gyr) and velocity dispersions. This mismatch between the scale height andthe velocity dispersion can lead to underestimates of the disc surface densityand a misleading conclusion of the sub-maximality of galaxy discs. In thispaper we present the study of the stellar velocity dispersion of the discgalaxy NGC 6946 using integrated star light and individual planetary nebulae asdynamical tracers. We demonstrate the presence of two kinematically distinctpopulations of tracers which contribute to the total stellar velocitydispersion. Thus, we are able to use the dispersion and the scale height of thesame dynamical population to derive the surface mass density of the disc over aradial extent. We find the disc of NGC 6946 to be closer to maximal with thebaryonic component contributing most of the radial gravitational field in theinner parts of the galaxy (Vmax(bar) = 0.76($\pm$0.14)Vmax).