The Large-Scale Distribution of HI in M33 and IC342

Extract

Distortions in the distribution of the HI in the outer parts of M33 are thought to be due to a warp in the HI plane. Measurements by Reakes and Newton with the Half Mile Telescope at Cambridge provide new evidence on the extent and kinematics of this gas. The integrated HI map with an angular resolution of 7 × 14 arcmin in shown in Fig 1a. The wings extend roughly symmetrically in outline to 70 arcmin (14 kpc) from the nucleus in the plane of the sky both to the NW and the SE. The radial velocity field in Fig lb shows large deviations from normal rotation in a plane in the outer parts. A model in which the gas rotates in circular orbits whose inclination and position angle of the major axis vary with radius, fits the HI distribution and kinematics quite well. Much larger extensions in R and z are required than in the model of Rogstad et al. (1976) and with a slower trend of i and P.A. with radius.