A truly "dark galaxy'" is an isolated halo consisting only of dark matter.
In some scenarios, it is possible that some optically dark objects
may contain enough HI that a blind HI survey would detect
them. A good example of a "dark" object is the southwestern component
of the binary system known as HI1225+01, discovered serendipitously
at Arecibo by Giovanelli & Haynes in 1989.
While the northeastern HI component
hosts a small, star forming dwarf, the SW component has no
detectable stellar counterpart. VLA observations reveal a velocity
field implying rotation with a peak rotational velocity of 14 km/s,
yielding a dynamical mass of 109 solar masses
and thus a dynamical mass-to-light ratio of 200
(Chengalur, Giovanelli & Haynes 1995). However, it is not
an isolated object, being part of an apparent binary system.
Find the original paper at:
Chengalur, Giovanelli & Haynes, Astronomical Journal, 109, 2415.
HI map of the binary system HI1225+01 made with the Very Large Array.
Click here for larger view.
Enlargement of the HI contours superposed on the optical images
of the NE component HI1225+01a.
Click here for larger view.
Both images are from Chengalur, Giovanelli & Haynes 1995.
Most recently,
Matsuoka et al. (2012) still find no associated starlight with HI1225+01b.
Last modified: Thu Aug 23 11:23:28 EDT 2007 by martha
