I imaged this galaxy on the 13th October - the night they got the miners out of the mine in Chile. I was up all night dashing between the television, watching the rescue and my observatory, making sure everything was going ok.

The target was Arp 212 in Pegasus. This is a galaxy that Halton Arp studied in the 60's when he compiled his Atlas of peculiar galaxies. He placed it the group 'Irregularities, Absorption, and Resolution'. The Atlas note is "narrow chaotic absorption tubes across one end". The atlas image intrigued me and I decided to try imaging it despite the small apparent size of the galaxy.

According to Arp, 'the distribution on the sky of clusters of galaxies shows significant association with relatively nearby, large, active galaxies. The clusters and the galaxies in them tend to be strong X-ray and radio emitters, and their redshifts occur at preferred redshift values. The central, low-redshift galaxies often show evidence of ejection in the direction of these higher redshift clusters. In all these respects the clusters resemble closely quasars which have been increasingly shown for the last 34 years to be similarly associated with active parent galaxies. Quasars are associated with Abell clusters of galaxies and he argues that, empirically, the quasars are ejected from active galaxies. They evolve to lower redshift with time, forming stars, and fragmenting at the end of their development into clusters of low-luminosity galaxies. The cluster galaxies can be at the same distance as their lower redshift parents because they still retain a component of their earlier, quasar intrinsic redshift.'

Because these observations are in such a strong contradiction with current belief that galaxy clusters are aggregates of luminous galaxies generally seen at great distances, I found it fascinating and worthy of further investigation. It appears that Arp has more recent investigations in hand and one of these involves NGC 7625.

This figure,



produced by Halton Arp, shows a large area around NGC 7625, mag. 12.8, a galaxy which appears to have undergone some internal disturbance. The outstanding feature is that there are only three bright Abell clusters in the area at 15.3, 15.3, and 15.1 mag. One pair is very well aligned across the galaxy and the third slightly off. The agreement of the redshifts at z = 0.040, 0.042, and 0.043 again is striking.

There are two bright radio quasars in the figure, but the most remarkable object is a strong X-ray source which is also a radio source. It is classified as a quasar (Mabs = -24.5 mag). Its redshift is z = 0.044, coinciding closely with the Abell clusters around NGC 7625. It looks like a transition between a quasar and a cluster and could be very important in gaining more empirical information on such a crucial link.

I had a look on Simbad and came up with this figure,



which shows the relationship of these Abell clusters around ngc 7625 and also some quasars in the vicinity.

My image,



50 x 120 sec exposures, shows none of these interesting features, they are outside the field of view, so I include these maps for information only, for those interested.

It just about shows some "narrow chaotic absorption tubes across one end" - I think!

Arp concludes his work on the subject as follows:

'The fact that the Abell clusters generally are found at greater distances outside the aligned quasars fulfills a prediction that was made before the cluster associations were found.' He then shows an empirical evolutionary scheme from the data that were in hand in 1997. Shown here:



It was noted at that time that the associations found required the quasars to drop in redshift as they aged and traveled outward and that at the stage where they were acquiring galaxy redshifts they were breaking into multiple galaxies. This is more or less exactly what he later found and represents a test of his earlier prediction.

I don't have a clue whether this could possibly be true but it is very interesting.