Rick -

Did you see http://adsabs.harvard.edu/abs/2007ApJ...658L..79W




On Mon, 26 Apr 2010 13:16:11 -0500, Rick Johnson
wrote:


Arp 169 is a trio of galaxies sharing a common envelope of stars, or at
least they appear to. Red shift would put these at about 340 million
light years. But studies using the D-sigma method which is often quite
accurate when applied to elliptical galaxies puts the distance much
closer, say about 280 million light years. The group appears to be part
of the ZWCl 2212.0+1326 galaxy cluster, a group of some 138 galaxies
about 338 light years. If so then the red shift distance is probably
correct. I suspect that the fact these are S0 galaxies and share a
common halo has skewed the D-sigma calculation. Still this galaxy
cluster has galaxies with red shifts that match the D-sigma value as
well. In any case its a ways from us.

Arp 169 is Arp's class: Galaxies (not classifiable as S or E) with
diffuse counter tails. I see mostly a common envelope of stars, not a
counter tail. I think Arp is referring to the somewhat north northeast
extension of the halo off the upper right galaxy NGC 7236. The middle
galaxy is NGC 7237 with the small galaxy to the southeast being NGC
7237C. Arp's comment; "Faint diffulse plumes coming away from two
galaxies. 3C442." This would indicate he sees a plume from NGC 7237 or
7237C as well. I see a hint of one, maybe. The reference to 3C442 is
because it seems to be coming from the core of NGC 7237. This could be
a sign they are actually interacting causing its black hole to be very
well fed at the moment. While one source describes these as elliptical
galaxies with no sign of recent star formation most describe all three
as blue compact S0 galaxies. From the color of the halos in my image
I'd agree with the latter. The halo doesn't have the orange color most
always seen with elliptical galaxies. Though there are some exceptions
3 in one spot would seem a bit too much of a coincidence to me anyway.

While most galaxy clusters are populted with elliptical galaxies as
their most common members this cluster seems to be mostly S0 galaxies.
I son't recall seeing so many one on image before. One of the few
exceptions is the face on, low surface brightness spiral south and a bit
west of Arp 169. It is CGCG 428-057 a 15th magnitude galaxy.

I've prepared a simple annotated chart showing distances to galaxies and
quasars that are not members of the galaxy cluster that NED had red
shift data for. There's a very blue quasar at 8.4 light years right
beside a galaxy that is quite likely far closer that the quasar. The
most distant galaxy I know of in the image is about half way toward the
lower right corner. It is SDSS J221402.08+134424.9 at a magnitude of
21.1. It must be a big one for me to see it at a distance of
4,300,000,000 light-years. Some how that looks much bigger than 4.3
billion light-years.

The rather bright asteroid is (88528) 2001 QU177 which is shining at
about magnitude 17.4.

Arp's 200" image:
http://nedwww.ipac.caltech.edu/level...ig_arp169.jpeg

14" LX200R @ f/10, L=4x10', RGB=2x10'x3, STL-11000XM, Paramount ME

Besides the full image at 1" per pixel I've attached a cropped version
at 0.75" per pixel.

Rick