Object of the Week, December 1, 2013 – Arp 113, NGC 67 – 72 Galaxy Group

[Howard B]

Arp 113 galaxy group

Galaxy Group
Andromeda
RA 00 18.37
DEC +30 04.0

MAG 13.3 (NGC 71) to 14.8 (NGC’s 67 and 69)

I came across this wonderful galaxy group for the first time on December 10, 2009 with my 28 inch f4 Newtonian. It was a cold, transparent night, the SQM read 21.32 and I used 408x for my observation and sketch:

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“Reminiscent of Stephan’s Quintet, only it’s better in that there are nine galaxies here! A beautiful group that was as much fun to look at as they were to sketch.”

The trio of NGC 68, 70 and 71 forms the bright, triangular focus of the group, and may be what Arp considered as the 113th entry in his catalog – they certainly seem that way in his Palomar 5 meter image.

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The distorted spiral NGC 70 and the elliptical galaxies NGC’s 68 and 71 make up this bright sub-group, but all three appeared much the same to me, each with a bright, nearly star-like core.

The remaining galaxies of this group are strung out in a ragged line from the three galaxies mentioned above, with NGC 69 appearing as the brightest in this line.

I’m looking forward to observing this group again on a better night to try and see the distorted spiral arms of NGC 70 and the central bar of NGC 72, along with a handful of fainter galaxies that may or may not be a physical part of this group. This wonderful image from Adam Block and the Mount Lemmon SkyCenter/University of Arizona shows a bunch of fainter targets to look for.

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List of data for all this group’s members at: http://de.wikipedia.org/wiki/VV_166

"GIVE IT A GO AND LET US KNOW"

[Ivan Maly]

Excellent target and observation. Curiously I see that while NGC 67 through 72 all belong to the interacting system VV 166, NED only considers NGC 70 as Arp 113. The Arp classification of his #113 however is "elliptical and elliptical-like galaxies close to and perturbing spirals".

[Uwe Glahn]

Very beautiful group Howard, thanks for the reminder. I have to revisit it with the 27". Looks, like the two PGC's E of NGC 70 and the pair of NGC 72A is in reach of the 27". I remember that the group is dimmer than the naked magnitudes suggests and that it was always a tough group for the 16" aperture. Here my sketch with the 16".

16", 230x, NELM 6m+
http://www.deepsky-visuell.de/Zeichnungen/NGC70-Gruppe.jpg

[Marko]

Caught this group 11/28/2008 at 338x from a sqm 21.1 site but I had noted transparency was off that night and seeing ok but not excellent. I missed Ngc67 (both of them) but that may also have been me not taking time to really study it and I was still 'earning my deep sky eyes' at that time. These are brief observations and I had called it the NGC70 group as well but the chart I used had one of the Ngc67s circled so I must have looked and not seen it being on the chart and so on (see attached megastar image). I have noted that Ngc72A was at my limits 30% of the time so perhaps the night would not have yielded the others anyway.

NGC 68 And MltG 00 18 18.5 +30 04 18 13.9p 1.2x 1.0' Ngc70_group: Just under 1' len, spherical.
NGC 69 And MltG 00 18 20.6 +30 02 22 14.8v 0.5x 0.4' Ngc70_group: 0.5' dia, smaller than 68, spherical similar mag.
NGC 70 And MltG 00 18 22.6 +30 04 46 14.2p 1.9x 1.2' Ngc70_group: Bright glow, in between 2 stars of similar mag
NGC 71 And MltG 00 18 23.7 +30 03 46 14.2b 1.2x 0.9' Ngc70_group: Just under 1' dia, spherical. Tiny dimmer than 68
NGC 72 And MltG 00 18 28.5 +30 02 24 13.4v 1.1x 1.0' Ngc70_group: Easy to spot, similar bright to 68
NGC 72A And MltG 00 18 34.4 +30 02 09 14.7v 0.5x 0.4' Ngc70_group: 1/4' dia? Averted only 30% time.
NGC 74 And Glxy 00 18 49.3 +30 03 42 15.5 1.0x 0.3' Ngc70_group: Limits of visibility. 80% averted, difficult to spot, used field stars
NGC 76 And Glxy 00 19 37.8 +29 56 01 14.0p 1.2x 1.0' Ngc70_group: 0.5' dia spherical, even fade, stellar core.

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[FaintFuzzies]

My observations from my 22" (taken from my Arp book)

22" f/4.1 reflector @ 305, 327 and 458x

Nice group of many galaxies. I could cram 10 galaxies in a 6.8’ field.

NGC 70, 71 and 68 form a perfect equilateral triangle about 1.2' on each side. All are bright and round with much brighter cores. All three are about 45" across. The interesting part of this trio is they all look like the same type of galaxy, but the core of NGC 70 is somewhat larger than NGC 68, which is a tiny bit larger than NGC 71. None of the interaction was detected in the 22” reflector.

NGC 67 - Faint and very small 2:1 elongated patch. Slightly brighter center. About 15" across and PA = 45º. To the SW lies MAC 0018+3003, which is a small slightly 3:2 elongated faint even surface brightness patch.

NGC 69 – Faint, small, slightly elongated even surface brightness patch, PA = 20º. About 15" long.

NGC 72 - Small round patch with a distinct stellar core with a very low surface brightness halo. About 40" across.

NGC 72A - Considerably bright, very small round patch. Slightly brighter center. About 15" across. MAC 0018+3002 located 45” east of NGC 72A is a very faint, very small round patch. Less than 10" across.

MAC 0018+3004A located 1.9’ east of NGC 70 is a very faint very small round patch. Less than 10” across.

NGC 74 (not in sketch) - Thin faint spindle about 30" across. Even surface brightness. PA = 135º

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[akarsh]

Hi

I had occasion to observe this group today. It's very beautiful! I didn't catch as many galaxies in the central region as Alvin, caught only 7.

Looks like a lesser known treasure!

Regards
Akarsh