Neutral hydrogen in the central part of the galactic system

Abstract

While trying to determine the rotation curve in 1953 Kwee, Muller, and Westerhout [1] found long and faint wings in the line profiles within 20 to 25 degrees longitude from the center. The gas responsible for these wings should therefore lie within 3 kiloparsecs from the center. The velocities of the neutral hydrogen causing these wings are far greater than could be expected on the basis of a reasonable rotational model of the Galaxy. Therefore, the wings were tentatively interpreted as being caused by high turbulent velocities in the gas. In view of the new and better data obtained with the 25-meter telescope in Dwingeloo, this interpretation has now been dropped. The new conclusion is that all of the neutral hydrogen in these regions is expanding and at the same time taking part in the galactic rotation. The evidence for this conclusion will be briefly presented.

Improving the triaxial bulge model of M31

“…Indeed, when submitted to a triaxial gravitational potential, the interstellar gas near the centre of a spiral galaxy can be found at higher velocities than expected from circular motion. Such anomalous velocities have been reported in several galaxies where no strong bar is visible, including the two nearest examples: the Milky Way (Rougoor & Oort 1959;Dame et al 2001) and the Andromeda galaxy (Lindblad 1956;Loinard et al 1999).…”

The Long Bar in the Milky Way: Corroboration of an Old Hypothesis

“…The story of the Galactic bar really begins with the discovery of large non-circular velocities in the 3 kpc and 135 km/s spiral arms (Rougoor & Oort 1960;Rougoor 1964). De Vaucouleurs (1964) was the first to attempt to explain the motions of these arms in terms of a non-axisymmetric potential (a bar) at the centre of the Galaxy.…”

Long‐term astronomical cycles as a consequence of cyclic time structure

“…There are numerous observations showing the occurrence of radial motions in almost every galaxy studied thus far. In the Galaxy expanding motions were reported by Rougoor and Oort (1959) and inward radial motions by McCutcheon (1970). In M31 expanding motions were detected by Munch (1960) and both outward and inward motions by Genkin (1962).…”