PGC 37639 has a recessional velocity of 10540 km/sec; its companion has a recessional velocity of 10520 km/sec. Based on their average recessional velocity of 10530 km/sec, a straightforward calculation indicates that they are about 490 million light years away. However, for objects at such distances, we should take into account the Universal expansion during the time it took their light to reach us. Doing that shows that they were about 470 million light years away at the time the light by which we see them was emitted, about 480 million years ago (the difference between the two values being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of 0.8 by 0.65 arcmin (counting its distorted extensions), PGC 37639 is about 110 thousand light years across. Its appearance was caused by a collision with its smaller neighbor (PGC 101374
) about a hundred million years before the moment in time at which we see the pair. Material stripped from the larger galaxy is seen as a line of brightly lit star-forming regions lying between the two, and gravitational compression of gases in the galaxies as a result of their collision caused multiple regions of unusually active star formation within each galaxy. The pair was used by the Arp Atlas as an example of a galaxy (PGC 37639) with material ejected from its nucleus (as noted, actually a separate galaxy, PGC 101374).
PGC 101374 is about 470 million light years away (see PGC 37639
for a discussion of how that is determined, and for images and a discussion of the pair's history). Given that and its apparent size of 0.4 by 0.25 arcmin, it is about 55 thousand light years across.
Thought to be the galaxy whose collision with NGC 4027
(which see) caused the strange appearance of that galaxy (and vice versa). Based on recessional velocity of 1745 km/sec, about 80 million light years away. Given that and apparent size of 0.9 by 0.6 arcmin, about 20 thousand light years across.