Object of the Week August 4th, 2019 – Arp 272 and the confusion that lies within

[Dragan]

Object of the Week August 4th, 2019 – Arp 272 and the confusion that lies within


NGC6050 (A&B?)
IC1179
Arp272
PGC57053 & PGC57058

Galaxies

Hercules

RA 16 05 23.3
DEC 17 45 26
(Coordinates centered on PGC57058, the eastern member)

Size: .9’x.7 (PGC57058)

Mag: 15.2 (PGC57058)

Member to the Hercules Cluster Abell 2151, Arp 272 is comprised of two interacting spiral galaxies – NGC 6050 & IC1179. Discovered by Lewis Swift on June 27th, 1886, this pair of galaxies lies approximately 500 million light years away.

I’m hoping that Steve will chime in here as I had much difficulty in discerning designations. So please take my designation with this week’s OOTW with a grain of salt. Best I can tell, NGC6050 is loosely given as the designation for both galaxies combined. PGC 57058 is the designation given to the brighter, eastern member per LEDA. This pair of galaxies were originally designated as NGC6050 A & B, and I’m beginning to believe that over time, data was erroneously commingled between the two galaxies. This may be a reason why I kept coming across confusing data for this pair. I hoping Steve can shed some light.

In hi resolution images, a 3rd galaxy can be seen, PGC 4019986. Distance measurements place this trio at approximately 500 Mly distant, but PGC57058 and PGC57053 are separated by each other by about 65Mly. If these measurements hold true, PGC 4019986 actually lies half way between the two main components. So in order of distance from us, when looking at an image, you are seeing PGC57058 in the foreground, PGC 4019986 next, then PGC57053 last. Just something I found interesting.

Observations online of this trio reveal that it can be seen in scopes as small as 16” from a pristine sky. This is a difficult object for sure. But what makes it attractive is not just the challenge, but that it lies in such a galaxy dense region of our sky. Give this object a chance. You may just be surprised. And if you strike out, pan around and look at all the beautiful smudges in the eyepiece. The entire area is a sight to behold.

And remember,
“Give it a go and let us know! Good luck and great viewing!”

3596
(Image Credit NASA/ESA/Hubble Collaboration/K. Noll/Hubble Heritage (STScI/AURA) (http://hubblesite.org/newscenter/archive/releases/2008/16/image/al/))

3597
(Image Credit NASA/ESA/Hubble Collaboration/K. Noll/Hubble Heritage (STScI/AURA) (http://hubblesite.org/newscenter/archive/releases/2008/16/image/al/))

[Steve Gottlieb]

The identifications are pretty much a mess (not uncommon with double or triple systems) with the southwest component (PGC 57053 on the HST image) variously referred to as IC 1179, NGC 6050A, NGC 6050B and even IC 1179B.

As Dragan mentioned Lewis Swift discovered the system – this was in 1886 with his 16" Clark refractor. The same night (June 27th) he discovered several other members of the galaxy cluster. To emphasize it was dim, he called it "eeeF; S; R; e difficult". Translate those e's into extremely or excessively.

Then two years later, Swift found the same galaxy while reobserving the Hercules Galaxy Cluster and reported it as a new discovery. He described it the second time as "eeeF; pS; R." Sounds pretty similar, right? It's just barely conceivable that he did see the much fainter companion on the southwest side, but since the main galaxy was so difficult (in 1886), it doesn't make any sense that he was able to resolve the much dimmer companion in 1888. And if that was the case, why wouldn't he call it double or refer to the brighter attached nebula?

If it seems odd that Swift would rediscover the same galaxy, it's not. For example in the summer 1897 (at the age of 77), he discovered the same pair of IC galaxies 4 times, each time reporting them as new!! As a result, IC 5007 = IC 5030 =IC 5041 = IC 5047 and IC 5003 = IC 5029 = IC 5039 = IC 5046. This pair is in Microscopium and when you make an observation, you can check off 8 IC numbers at once!

So, according to the historical record, NGC 6050 = IC 1179 refers to the entire system. The southwest galaxy is probably best referred to as PGC 57053 (as labeled in the image) or perhaps NGC 6050B to associate it with NGC 6050.

By the way, to find data on PGC 4019866 in LEDA, you have to search under SDSSJ160522.48+174534.7 (http://leda.univ-lyon1.fr/ledacat.cgi?SDSSJ160522.48%2B174534.7&ob=ra).

In Jimi's 48" at low power (that's 375x), I described PGC 57053 as a faint, diffuse glow attached to the southwest side [of NGC 6050]. It displayed a very weak central brightening and a very faint nucleus. Although the HST image shows two distinct galaxies, at least at this power it wasn't cleanly resolved.

[Jimi Lowrey]

What a great field. I have heard this galaxy called the “heart”. It is funny that I had it on my list last week at the Oregon Star party but did not Observe it.

[Steve Gottlieb]

I just checked my notes and I've logged a total of 40 members of the Hercules Galaxy Cluster just in a 25' field centered on NGC 6050 -- taking notes at the eyepiece on a printed SDSS image of the field. Many of the fainter ones were much closer to NGC 6050 and only observed through Jimi's scope.

The warped edge-on NGC 6045 and NGC 6045B dangling from its tip (Arp 71) right next door is another great pair. Probably deserves a nickname.