VV 171 and friends

[Steve Gottlieb]

On Saturday night (22 March) I took a look at the tight galaxy chain (3 components) VV 171 = UGC 4991 for the first time. The three galaxies are lined up in a 1' string N-S with the center one tougher, partly because of a superimposed star. I wasn't expecting, though, a fairly rich, compact cluster. Here's the SDSS image of the field, along with computed V mags (roughly averaging G and R) and identifications (Megastar has several misidentifications). All the labeled galaxies were visible in my 24-inch at 375x and fit in the 11' field of my 6mm Delos! LEDA 1667862 was the faintest one picked up (V = 16.2) at my "nearby" observing site (Lake Sonoma), which is at the edge of blue/green light-polution zones.

If the image is displayed as a thumbnail, I'll post a more complete report on Adventures in Deep Space with a high-rez image. I should mention that VV 171 is located in western Leo at 09 23.4 +22 19, a couple of degrees northwest of NGC 2903.

VV 171 = UGC 4991.jpg

[Ivan Maly]

Interesting field, and I imagine it was great to discover how rich it was. I looked in NED and it appears that UGC 4991 (not 3991) is the two western members of the VV. Further, the entire large group seems to be (I did not check the individual memberships) WBL 219 from the catalog of nearby poor galaxy clusters. All is relative, of course, and the distance of this one is >400 Mly.

[Steve Gottlieb]

Thanks for fixing that typo (I just edited my post), Ivan. I checked all the redshifts and they are nearly identical (z = .03), which gives a light-travel time of roughly 400 Mly as you mention. The cluster is indeed WBL 219, although the paper only gives lists 5 members.

[obrazell]

what is the reference for the WBL catoague? i know i had it once but forgot

Owen

[Steve Gottlieb]

A Catalog of Nearby Poor Clusters of Galaxies by Richard White et al in AJ, Volume 118, Issue 5, pp. 2014-2037. The abstract reads

"A catalog of 732 optically selected, nearby poor clusters of galaxies covering the entire sky north of -3 deg declination is presented. The poor clusters, called WBL clusters, were identified as concentrations of three or more galaxies with photographic magnitudes brighter than 15.7, possessing a galaxy surface overdensity of 10^(4/3). These criteria are consistent with those used in the identification of the original Yerkes poor clusters, and this new catalog substantially increases the sample size of such objects. These poor clusters cover the entire range of galaxy associations up to and including Abell clusters, systematically including poor and rich galaxy systems spanning over 3 orders of magnitude in the cluster mass function. As a result, this new catalog contains a greater diversity of richness and structures than other group catalogs, such as the Hickson and Yerkes catalogs. The information on individual galaxies includes redshifts and cross-references to other galaxy catalogs. The entries for the clusters include redshift (where available) and cross-references to other group and cluster catalogs."

The Yerkes catalogs refers to the MKW groups and AWM groups (more acronyms to remember!)

[Uwe Glahn]

Steve,

I overlooked the middle galaxy (VV 171b) because of the superimposed star and soft seeing. Could you separate star and galaxy?

27", 586x, NELM 6m5+, Seeing III

[obrazell]

Thanks Steve. Just back from 5 washed out nights at one of the major star parties here :-(

Owen

[Steve Gottlieb]

It was highly suspected but I couldn't confirm it with confidence. I was hoping to get another look this weekend under better conditions, but we were clouded this past weekend in northern California.