On the circular velocity in the andromeda galaxy

By analysing a sample of 158 globular clusters belonging to the galaxy M 31 or Andromeda Nebula (AN) in the framework of a spherically symmetric model with constant circular velocity a value of 260 ± 40 kms^–1 for this quantity is obtained. It is also found that the number density of AN globulars roughly decreases as the cube of the distance to the centre with a cutoff radius of about 40 kpc. The implied AN mass within this cutoff is about 0.6 TM (1 TM = 10¹² M ). Bearing in mind the model limitations this mass is rather an upper limit. The present results suggest 1.5 as a probable value for the mass ratio of AN to the Milky Way unless their massive dark coronae are significantly different in size.The velocity distribution of AN globulars seems to be close to isotropic.