Lmc & smc

[speach]

Are these two galaxies old or new? If they are old they seem to be dispersing, or if new not yet coalesced. As all galaxies seem to have black holes at their centres, again if old the BH have evaporated, if new the BH hasn't yet formed.

[barx1963]

Hmmm... not sure there is evidence ALL galaxies have a black hole? Certainly the vast majority of large galaxies seem to, but my understanding is that dwarf galaxies do not. And even if the MCs did, not sure that evaporation of black holes (I assume you are talking about evaporation by the Hawking radiation process) would have enough time even in the 13 billion years of the universes existence to do the job. I think I read somewhere that calculations show that solar mass black holes would still only radiate at a much lower temperature than the CMB, so would still absorb energy (and hence mass) from the CMB. The larger Black Holes found in galaxy centres would be even colder so we will have to wait until the universe is much larger and colder before they start evaporating.

Malcolm

[Atmos]

All galaxies are old and formed towards the beginning of the universe. Some of the more isolated ones, if they haven't interacted gravitationally, remain small and are not overly active.

Not all galaxies have SMBHs at their centre. Spiral and elliptical galaxies do but I doubt most irregular dwarf galaxies would. They would undoubtedly contain stellar mass black holes along to possibly having those elusive intermediate mass (100-10,000 solar mass) ones. Supermassive black holes largely form through galaxy interactions, whether it be through gravitational interactions driving black holes into the centre OR massive black hole mergers between dwarf and larger galaxies.

[brisen]

The LMC is experiencing the effects of tidal disruption from the gravitational effect of the Milky Way and to a lesser degree from the SMC. The effect of the tidal disruption is such that the spiral arms of the LMC have been torn apart and appear dispersed from our viewpoint.

Brian

[Max Vondel]

SMBH evaporation takes place after the final stars have died...many many times the age of the universe at present