Galaxies and Quasars
In his book Quasars, Redshifts and Controversies, Halton Arp discusses quasars associated with M33. Figure 8.12 shows a line of high redshift quasars lying between M33 and M31, the Andromeda galaxy. There is also a concentration of low redshift quasars near M33.
Note that Andromeda has a possible binary black hole system at its core. The quasar data suggests a strong interaction between M33 and M31. This lends support to the unpopular idea that the central black holes, or lack thereof, of such galaxy pairs are not independent. A possible relation between high $z$ quasars and AGNs is discussed here.