Intermediate-mass BH: how to form them?
1
...and how to observe them?
Optical counterparts, lightcurves, accretion disk lines
obtain mass function
ß primordial  (see eg Rees)
                                 feeding  -- from a molecular cloud? (Grindlay)
                                               -- by capturing a companion?           
ß in globular clusters    from SN explosion of very massive stars?
                                                 (from merging of many smaller BH?)
NO. Ineffective because of slingshot effect
ß in super star clusters    ( = young globular clusters?)
                              from merging of many stars à star of 500 Msun 
                              à sinks to the cluster centre à SN à IMBH?
(eg, Ebisuzaki et al 2001)