Object of the Week Aug,7 2022-UGC 10321-A Compact Group That Hickson Missed

[Jimi Lowrey]

UGC 10321
Hercules
RA
16 18 05
Dec
+21 33 13
A-LEDA 57765 V MAG 15.5
B-LEDA 20036 V MAG 17
C-LEDA 57770 V MAG 16
D-LEDA 200337 V MAG 17.8
All MAG are + or - from the SDSS photometry
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The UGC catalog calls this a multi galaxy group. It also has a VV catalog number VV129. I found the VV numbers really confusing. I hand labeled a image to make it simpler for me to discuss hear. This is for sure a compact group Paul Hickson missed in his famous catalog.

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What makes this group so interesting to me is one of it’s galaxies B is way in the background. It has a light travel time of 1.55 billion light year’s. The other galaxies A C and D are interacting at 469 million light years away. This makes this group a rare chance alignment.

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I observed this group several nights this last dark period. I found at 610X A B and D all looked like one long galaxy. I was surprised how easy B the most distant one was. I found D to be the most difficult of the group. I could only glimpse it every now and then. I only could see it with averted vision a small percentage of time. C galaxy was easy for me I could see it constantly.

This is a really interesting galaxy group although it is some what of a challenge object.I look forward to reading your results. As always———

Give It A GO!
Good Luck and Great Viewing

[Clear Skies]

An interesting but very faint group. Out of reach of my gear, but fun to delve into nonetheless.

Boris Vorontsov-Vel'yaminov (https://en.wikipedia.org/wiki/Boris_Vorontsov-Velyaminov) marked five galaxies as members of this group, A through E.

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Source: http://ned.ipac.caltech.edu/level5/VV_Cat/Figures/VV129.jpeg
North is to the left, west is up.

Unfortunately, the group was not described in the 1977 paper 1977A&AS...28....1V (https://ui.adsabs.harvard.edu/abs/1977A%26AS...28....1V/abstract). It is listed in his MCG notes - 2001A&AT...20..717V (https://ui.adsabs.harvard.edu/abs/2001A%26AT...20..717V/abstract), but only as a "disrupted nest" with 5 members.

Taking a closer look at the group, on different images including SDSS and PanSTARRS (Aladin (https://aladin.unistra.fr/AladinLite/?target=16%2018%207.368%2B21%2033%2043.81&fov=0.13&survey=CDS%2FP%2FSDSS9%2Fcolor)), the question can be raised whether or not VV's group member B (SDSS J161806.05+213323.8 (http://skyserver.sdss.org/dr16/en/tools/explore/summary.aspx?ra=16+18+06.038&dec=%2B21+33+24.13)) is a part of the galaxy MCG+04-38-046 (PGC57765) that is marked as A. It may be a disrupted arm, or a merger perhaps.

North of A & B is C. Pretty much every available image, including the POSS1 plate (https://archive.stsci.edu/cgi-bin/dss_search?v=poss1_blue&r=16+18+06.30&d=%2B21+33+39.0&e=J2000&h=5&w=5&f=gif&c=none&fov=NONE&v3=) from the year 1950 (presumably used by VV'), make it quite clear that there is more than one galaxy: C consist of the northwestern galaxy PGC200336 (SDSS J161805.74+2133484.4 (http://skyserver.sdss.org/dr16/en/tools/explore/summary.aspx?ra=16+18+05.76&dec=21+33+48.7#)) and southeastern SDSS J161806.04+213345.2 (http://skyserver.sdss.org/dr16/en/tools/explore/Summary.aspx?id=1237662223553986757). NED says the southeastern is a star (http://ned.ipac.caltech.edu/cgi-bin/objsearch?objname=2mass+16180602%2B2133455&extend=no&hconst=73&omegam=0.27&omegav=0.73&corr_z=1&out_csys=Equatorial&out_equinox=J2000.0&obj_sort=RA+or+Longitude&of=pre_text&zv_breaker=30000.0&list_limit=5&img_stamp=YES), but it clearly is not.

North of the galaxies that are VV' 219C is D - PGC200337 (SDSS J161805.47+213411.9 (http://skyserver.sdss.org/dr16/en/tools/explore/summary.aspx?ra=16+18+06.038&dec=%2B21+33+24.13)).

To the east, visually detached from members A through D, is the fifth (sixth?) galaxy VV 219E - MCG+04-38-047 (PGC57770).

All visualised in this observing guide:

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Click here (https://clearskies.eu/csog/downloads/dsfootw2022/#32) to download it as a pdf.

Cheers,


Victor

[Steve Gottlieb]

I've observed the three brightest members in my 24", labeled A, B and C in Jimi's image, though my notes I used the VV (Vortontsov-Velyaminov) lettering. I assume the seeing was subpar since I used lower than usual magnification.

24" (7/7/13): at 282x, three components of VV 129 were resolved. VV 129a, the brightest member, appeared very faint, small, round, ~0.3' diameter, visible continuously. VV 129c, just 35" N, appeared extremely faint, small, round, 10" diameter. VV 129e (MCG +04-38-047) lies 1.1' NE and appeared extremely faint (V = 16.2), very small, round, 0.2' diameter. I couldn't hold the latter galaxy continuously but it was repeatedly seen and confirmed. A quartet of mag 14-15.5 stars (similar size to VV 129) is less than 2' S. Two nearby galaxies were also observed: CGCG 137-077 lies 10' E and also LEDA 1650738 (V = 16.1) is 5' S.

[FaintFuzzies]

I also observed A, B and C labelled in Jimi's image. My notes below are from the VV labeled designations, which is the same as Victor's image above.

22” f/4 (287 and 383x) – only three of the five members was detected. I didn’t try 690x, so this is an “observe again” object.
VV 129a is a very faint small round diffuse glow. 0.2’ across.
VV 129c is extremely faint very small round glow. Lies 0.5’ due north of VV 129a. 0.1’ across.
VV 129e is also extremely faint small round glow. 1.0’ ENE from VV 129a. 0.1’ across.
The other two members were not seen.

The condition were not as ideal as it could be. NELM was 6.2 to 6.5.

Here is the link to the observing notes (scroll to the bottom)
http://www.faintfuzzies.com/OR-Jun082013-BC.html

[Jimi Lowrey]

Looking at the legacy survey image which is the deepest of any survey at this time I only see 4 galaxies here. What V V listed as B is just tidal interactions with a H II knot.

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[Uwe Glahn]

This group looks much more interesting in the scope than on the POSS plates.

I noted: A: laminar, steadily visible with averted vision; B and C clear sighting with averted vision for seconds each, especially C much brighter than expected; D at the limit, stellar but popping in and out of view several times

sketch: 27", 419x-586x, NELM 6m5+, Seeing II-III
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home (http://www.deepsky-visuell.de/Zeichnungen/UGC10321.htm)