Strong evidence for galactic ejection vs capture in interactions. As I mentioned in another thread (relative to PG 1012+008), it is common for mainstream astronomers to treat apparently interacting extra-galactic objects as though they are either being captured or are colliding with one another. The possibility that the larger object ejected the smaller is rarely touched on, except by Arp and others that are looking for definitive interactions of objects that are discordantly redshifted. I have been looking in atlases and catalogs for nearby spirals with well-associated companions, jotting down their redshifts, etc, in an attempt to see if (as Arp suggests) companion galaxies are preferentially redshifted with regard to their hosts, and to find examples of companions that are apparently interacting and NOT chance projections. While searching for surveys or studies done in non-optical wavelengths, I found this great image of M83. There is a nearby companion that seems unrelated in the optical images, but is directly connected to M83 when imaged in HI. It is Figure 2. http://www.nrao.edu/astrores/HIrogues/webGallery/RoguesGallery01.html Here is an abstract of the article in which the above data were presented. http://adsabs.harvard.edu/cgi-bin/n...&return_fmt=LONG&db_key=AST&nocookieset=1 To bolster the case for ejection of the companion, here is HST and Chandra imagery of the nucleus of M83 - a VERY busy place with asymmetrical distribution of mass. http://www.mssl.ucl.ac.uk/~rs1/M83.html And here is a paper describing the nucleus of M83. The authors characterise it as a double nucleus. The Chandra and HST imagery suggest to me that we might be looking at the beginning of another ejection event. In a hundred million years or so, we should know for sure. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2000A&A...364L..47T Now, a question. Does anybody know the name of the apparently ejected companion of M83? It's a silly thing, but I can't seem to find mention of it in relation to M83, and although I found the abstract to the Park et al paper(Full-Coverage K and HI Mosaic Images of NGC 253 and M83), I can't seem to find a full text version of it. I would love to know what the measured redshift of the companion is, though. It is by now quite far away from M83, but if Arp is right, it should still have some excess redshift relative to M83.