The distribution of HI in the lenticular galaxy NGC 2787.

The Westerbork Synthesis Radio Telescope was used to map the H I distribution in the lenticular galaxy NGC 2787. The neutral hydrogen is found to be distributed in an approximately circular ring of 6arcmin.4 diameter, nearly twice the optical size of the galaxy. The apparent major axis of the H I distribution is significantly misaligned relative to the principal plane of the stellar distribution, suggesting the presence of an extended dark halo. Further evidence for unseen matter is the large rotational amplitude of the H I, with an extreme value of 169/(sin i) km s^-1. Using a derived inclination of i = 42°, the resulting total mass-to-light ratio has the remarkably high value of 50 (solar units).