Aperture synthesis study of neutral hydrogen in NGC 2403 and NGC 4236. II. Discussion
1973; EDP Sciences; Volume: 24; Linguagem: Inglês
ISSN
1432-0746
Autores Tópico(s)Astrophysics and Star Formation Studies
ResumoFor both NGC 2403 and NGC 4236 the extert of their H I distributions, as defined by 20% contour levels, is coincident with their optical extent. Both distributions exhibit bright, unresolved lumps situated in regions of prominent H II emission. The rotational velocities in NGC 2403 reach a maximum at 9 kpc, thereafter remainlng relatively constant, thus suggesting that the bulk of this galaxy's mass lies outside its optical radius. NGC 4236, assumed to be a barred spiral, exhibits solid-body rotation over the length of the bar. Peculiar motions in NGC 2403 of ~l0 km s/sup -1/ are observed, and are consistent in position and amplitude with the nonlinear density-wave theory of spiral structure. Upper limits to the fractional H I masses of these objects are l0% (NGC 2403) and 9% (NGC 4236). (auth)
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