Mauri Valtonen

OJ 287 - binary pair of supermassive black holes

A historical light curve of the BL Lacertae object OJ 287 is constructed in the optical V band using observations between 1890 and the present. The curve exhibits periodic outbursts at intervals of 11.6 yr or 9 yr. The individual outbursts show an initial maximum with decaying submaxima at intervals of about 1 month. It is proposed that these characteristics are caused by a binary in the nucleus of OJ 287, with the binary members having an accretion disk around them. The outbursts at 9-yr intervals would be caused by the tidal action of the companion on the disk of the larger black hole. A computer simulation is used to demonstrate that the inflow into the center of such a disk during the repeated periastron passages of a companion will produce an outburst similar to the ones observed. Based on indirect evidence, probable masses of 5 billion solar and 20 million solar are determined for the two objects. 38 references.

Tidal generation of active spirals and S0 galaxies by rich clusters

Gavazzi and Jaffe found that late-type spiral galaxies in rich clusters are radio sources 10 times more powerful than spirals outside clusters. Gavazzi and Jaffe propose that ram pressure from the cluster medium causes collapse of dense molecular clouds, star formation, and other activity in the spirals disks. Bothun and Dressler similarly explain blue H I poor disk galaxies found in the central regions of the Coma Cluster via ram pressure effects. With computer simulations, it is shown in the present work that the tidal field of the cluster as a whole is physically sufficient to trigger cluster spiral nuclear and disk activity. It is shown that tidally induced collisions of disk gas clouds should be much more effective than ram pressure in causing activity. The observed tendency for disk galaxies in centers of rich clusters to be barred and S0 is explained as due to the cluster tidal field. Metals in the cluster medium would be enhanced by the expulsion of spirals enriched gas via tidally induced activity. 36 refs.

Binary pairs of supermassive black holes - Formation in merging galaxies

A process in which supermassive binary blackholes are formed in nuclei of supergiant galaxies due to galaxy mergers is examined. There is growing evidence that mergers of galaxies are common and that supermassive black holes in center of galaxies are also common. Consequently, it is expected that binary black holes should arise in connection with galaxy mergers. The merger process in a galaxy modeled after M87 is considered. The capture probability of a companion is derived as a function of its mass. Assuming a correlation between the galaxy mass and the blackholes mass, the expected mass ratio in binary black holes is calculated. The binary black holes formed in this process are long lived, surviving longer than the Hubble time unless they are perturbed by black holes from successive mergers. The properties of these binaries agree with Gaskells (1988) observational work on quasars and its interpretation in terms of binary black holes. 39 refs.