Max Planck Institute for Astronomy - Annual Report 2007

58 II. Highlights
NGC5055 (M63) NGC628 (M74)
NGC3031 (M81) NGC5194 (M51)
Fig. II.8.2: Several examples of the galaxies observed within
the tH i N g s project; left (this page): Spiral galaxies; right (Page
59): Dwarf galaxies. The radio maps are coded in blue; with
an overlay of infrared images (coded in yellow, they show the
then approximate a constant value as the distance to the
core region grows. The curves of faint galaxies slowly
increase and do not reach a constant level within the
HI area.
Mass models of the galaxies, including dark matter,
could be obtained from the measured rotation curves
and these could be related to the baryonic masses derived
from the sp i t z e r data. Here it became clear that in
bright galaxies the influence of dark matter increases as
the radius grows but that the ratio of dark to baryonic
matter is never as large as in faint galaxies. Bright gal-
distribution of the old stars) and a combination of infrared and
ultraviolet (coded in violet, they show the distribution of the
star formation regions).
axies are thus not so strongly dominated by dark matter
as faint galaxies, and in particular dwarf galaxies. In the
latter, the dark matter comprises over 90 percent of the
total matter.
With the existing data, the group then approached the
question of the mass distribution of dark matter. Would
it be possible to distinguish between the “cuspy core”
model and the “soft core” model as was suggested by
observations?
Fig. II.8.5 shows all rotation curves (grey) as well
as an averaged curve (black squares). Furthermore, the