Not the most impressive of images but one which may hold some interest to galactic interaction imagers. Imaging is not always about taking a 'pretty picture' but often to finding out as much as we can about the objects we image. I'm quite happy to consider somewhat unorthodox theories if they crop up during my research, that's how I got interested in Halton Arp's work and his somewhat eccentric theories. Although his work has been largely disproved and discredited nowadays, there is always a little doubt in my mind that just maybe he could be right on some things! Some current astronomy theories just don't seem to sit quite right to my mind.

So here is Arp 42, NGC 5829, an example of the 'Spiral with LSB Companions on Arms' classification by Halton Arp. The Atlas note says "faint bifurcated arm to comp. one faint arm on comp. coiled same direction as parent".

NGC 5829 and IC 4526 make up Arp 42, an example of a spiral galaxy with a faint companion; but the two are not physical companions, as IC 4526 is over 300 million light years further away. The galaxy is also listed as a member of Hickson Compact Group 73, but is not actually a physical member of the group, being much closer than all the other members.

Based on a recessional velocity of 5635 km/sec, NGC 5829 is about 260 million light years away, in unusually poor agreement with redshift-independent distance estimates of 145 to 175 million light years. Using an intermediate distance of 200 million light years, the galaxy's apparent size of 1.45 by 1.0 arcmin would correspond to 110 thousand light years.

There are a lot of very faint galaxies in the field. NGC 5829 and IC 4526 are the 2 major players. These two, plus three of the small galaxies nearby, form the Hickson Galaxy Cluster 73. Also there are two more tiny galaxies at the end of the arm which swings across the top of NGC 5829, north of the core. Also the whole group lies right at the north edge of Abell Galaxy Cluster 2017, and you can see loads of tiny galaxies in the southern half of the field.

The Arp atlas image can be seen here;

http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp42.jpeg

Although Arp doesn't discuss it, the fact that ngc 5829 has a redshift of z=0.0188 and ic4526 has a very different redshift of z=0.0456, would have probably raised some questions in his mind. Did he see, or imagine, a bridge between the 2 galaxies in his image? I can almost. Can you? If you can the implications are quite interesting.