21 cm Observations of NGC 45

Abstract

Observations of NGC 45 have been made at a wavelength of 21 cm using the radio telescope at Parkes. Line profiles have been measured for a grid of 44 points spaced at intervals of 6' arc. From the measurements the mass of neutral hydrogen is calculated to be 8·2 × 108 M?, assuming a distance of 3 Mpc. A simple self-consistent model is determined by computing line profiles to compare directly with the observations. This enables the rotation curve to be corrected for the first-order effects of beam smoothing and results in a total limiting mass of 2·5 × 1010 M?.