21 cm observations of NGC 55

Abstract

Observations of the irregular galaxy NGC 55 have been made at a wavelength of 21 cm using the 210 ft radio telescope at Parkes. Line profiles have been measured for a grid of 60 points spaced at intervals of 6 min of arc. The mass of neutral hydrogen in the system is 2 ·0 X 109 1110, assuming a distance of l • 74 Mpc. The peaks of the profiles delineate a well-defined rotation curve, from which the total mass is found to be 2 • 5 x l 010 1vf 0. The centroid of the hydrogen distribution and the centre of rotational symmetry are both displaced by about 3 min of arc from the nucleus of the system.