What is UGC 3583?

[Ernie Ostuno]

Hello, this is my first post here. I have been observing for about 40 years. My latest project is to observe open clusters that are not plotted in Uranometria 2000. A couple nights ago I observed OCL 486 from the Alter et al (1970) list of open clusters. It is a fairly compact group of 14th to 16th magnitude stars at RA 06h 53 04.2 and Dec +16 55' 39.0. It looks like either an open cluster or a distant globular cluster. It does NOT look like a galaxy, but somehow managed to be listed in the UGC, ZWG and MCG catalogues of galaxies, which give it a magnitude of 14.2 and dimensions of 1.23' x 0.6'. The UGC lists it as 3583 and notes that it may be a "galaxy system". A close examination of the object on sky-map.org shows a very small and faint galaxy at 06h 53 14.78, +16 54' 58.8, but this object is not large or bright enough to be UGC 3583 and the other "galaxies" in the "system" appear to be stars.

So the question is how did a star cluster get mistaken for a galaxy? A more intriguing question is this cluster possibly a globular cluster? I have searched the internet for more recent catalogues that may include this object, but as of yet have not found it listed anywhere. Any insight into this mystery will be appreciated.

[Steve Gottlieb]

Hi Ernie, welcome to the forum!

Here's my observation of UGC 3583 from 2011 using an 18". This object was also catalogued as Berkeley 29 (open cluster). It is somewhat surprising that the UGC, CGCG and MCG mistook it for a galaxy.

18" (12/22/11): at 175x, a fairly faint, roundish 2' spot was immediately seen with a couple of stars superimposed or resolved. At 285x, 5 or 6 mag 14-15.5 stars were resolved over the unresolved background haze. A 1.7' line of three mag 11 stars oriented N-S is 3' W of the cluster and a mag 10 star is off the east side.

This is an old open cluster with age of 3.5-4.5 billion years and may be associated with the Sagittarius Dwarf galaxy (SagDEG) (see "Accreted versus In Situ Milky Way Globular Clusters" MNRAS, 2010. A 2005 paper titled "Berkeley 29, the most distant old open cluster (http://arxiv.org/abs/astro-ph/0408078)" in A&A, 429, 881 places the cluster in the anticenter direction at a galactocentric distance of 70,000 light years and nearly 50,000 light years from the Sun.

Here's an image by Rick Johnson that was posted on CloudyNights two years back. His full post is here (https://www.cloudynights.com/topic/530908-berkeley-29-a-distant-old-open-star-cluster/).

2933

[Steve Gottlieb]

This (http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1988PASP..100.1423M&data_type=PDF_H IGH&whole_paper=YES&type=PRINTER&filetype=.pdf) 1988 paper on "Redshifts of Galaxies in the Winter Plane" has a note "UGC 3583 is an open star cluster also known as Berkeley 29 or OCL 486 (Setteducati and Weaver 1960; Alter, Balázs, and Ruprecht 1970). These objects should not be confused with galaxies in the future."

[Ernie Ostuno]

Thanks, Steve! I had a feeling you'd have an answer, but still impressed at how quick and detailed. I didn't know it was on the list of Berkely clusters. Tosi et al (2005) mentions that it could be part of the Canis Major dwarf galaxy that is merging with the Milky Way, which would explain the great distance and age of the cluster. It is strange how this object made it into so many galaxy catalogues. I was hoping that it was a globular, given the lack of globulars along that stretch of the Milky Way. While I was searching for info on Be 29/OCL 486 I did find that there was a recently discovered, very low luminosity globular in Gemini: Koposov 2 is at 07h 58 17.0, +26 15' 18. The reference is here. (http://iopscience.iop.org/article/10.1086/521422) The cluster stars appear to be fainter than 17th magnitude, so visual observation would be quite the challenge!

[Dragan]

Hi Ernie,

Welcome to DSF. We sure hope you enjoy our little family here.

As to Steve, he never fails to impress, does he? He's such a valuable asset to our hobby. :)

[Ernie Ostuno]

Thanks, Dragan. This is a great forum. I'll try to contribute observations of interesting objects as I find and observe them.

I first corresponded with Steve before the internet was much of a thing, if you can believe that. He is THE authority on all things faint and fuzzy in the celestial realm!

[Steve Gottlieb]

Thanks, Ernie. By the way, I just took a look at the UGC (print version) and the classification says "Resolved dwarf system?", but in the notes section it adds the comment "star cluster?", so back then the incorrect galaxy classification was questioned.

[Ernie Ostuno]

Steve, since Zwicky or Vorontsov-Velyaminov have it listed in their catalogs, I'm guessing the error was copied by the UGC. I'll have to look through the CGCG to see if Zwicky commented on it. On another note, I am now going through the Berkeley list of clusters that aren't included in Uranometria 2000.0. I am having trouble tracking down Berkeley 24. I can't find a link to the original list of clusters and it doesn't appear obvious at the coordinates given in this listing (http://evaconline.org/obspgm-berkeley.html). There is a knot of stars surrounding a small HII region at 06h 38 27, +00 44 43, but it doesn't look like much of a cluster.

[obrazell]

Are you sure you have the right location? Everything I have gives 06:37:48 -00°52'00" and there could be a cluster at that point.

Owen

[Bruce Sokol]

Steve , your nickname should be Steveopedia. Thanks for all you have done for deep sky nuts like myself. Hope to see you again
at Grandview this summer.

[Ernie Ostuno]

Are you sure you have the right location? Everything I have gives 06:37:48 -00°52'00" and there could be a cluster at that point.

Owen

Thanks, Owen! There is indeed a cluster there. The source I listed was in error on the coordinates of Berkeley 24 and at least one other cluster on the list. That was the only online source I could find for the Berkeley clusters. What sources are do you have?

[Ernie Ostuno]

I just looked through the Zwicky CGCG and the error calling the open cluster Berkeley 29 a "resolved dwarf system" was found in Volume II, Page 2 (field number 85, POSS Plate 417) published in 1963. This predates the UGC but may be around the same time the MCG was being compiled, so I am not sure if the error originated in the CGCG or the MCG.

[obrazell]

I was looking in the Clear Skies guide which has one dedicated to the Berkley clusters as doe sthe Bafk which also has a guide dedicated to the Berkley clusters.

Owen

[Steve Gottlieb]

I just looked through the Zwicky CGCG and the error calling the open cluster Berkeley 29 a "resolved dwarf system" was found in Volume II, Page 2 (field number 85, POSS Plate 417) published in 1963. This predates the UGC but may be around the same time the MCG was being compiled, so I am not sure if the error originated in the CGCG or the MCG.

Yep, I see that. I have Volume II through VI of the CGCG in my library (purchased at the Caltech bookstore several decades ago), but don't have Volume I, which wasn't available (only a photocopy). And only a digital version of the MCG, when it was available from the ADC on CD-ROMs.

[Steve Gottlieb]

Steve, since Zwicky or Vorontsov-Velyaminov have it listed in their catalogs, I'm guessing the error was copied by the UGC. I'll have to look through the CGCG to see if Zwicky commented on it. On another note, I am now going through the Berkeley list of clusters that aren't included in Uranometria 2000.0. I am having trouble tracking down Berkeley 24. I can't find a link to the original list of clusters and it doesn't appear obvious at the coordinates given in this listing (http://evaconline.org/obspgm-berkeley.html). There is a knot of stars surrounding a small HII region at 06h 38 27, +00 44 43, but it doesn't look like much of a cluster.

Brent Archinal and Steven Hynes give a position of 06h 37m 47s -00° 52.7' in their book Star Clusters. They also discuss (in the notes section of the book) the source of the error in the website you linked ---

In the Lund Catalogue main data file, the minus sign is missing for the declination in the 1950.0 and 2000.0 positions (it is present in the "print" file). The correct position, from Brian Skiff's [private communication, 1995] measurement on the DSS, (2000) 06h 37m 47s -00° 52.7'. The declination is similarly corrected (but the position is not as good as Skiff's) in the CDS version of February 20, 1995. In addition, the Lund Catalogue alias list is missing the identity "OCl 539" for this object (see. e.g. Ruprecht et al [1981]).