Cold Gas in Late-Type Galaxies

Abstract

In the last two decades a large number of spiral galaxies have been studied in the 21-cm line. These studies have revealed the density distribution and kinematics of HI and have provided the measurements of the total mass and the mass distribution in those systems. This has led to the classic picture for HI disks: spiral arm structure, warping in the outer parts and flat rotation curves. Naturally, in the early studies attention was drawn to the large-scale properties and regularities. In recent studies, a more detailed picture has been emerging. Furthermore, the connection between the effects of environment and peculiarities in the HI distribution are being investigated. Here, the “classic” picture will be briefly described: the main emphasis will be on some of the more recent, less well-known findings.