Ugc8837 and Ngc5474 near M101

[Marko]

Howards piece on M101 ends in a 'While You're Here' comment that discusses Ngc5474 which I hope to revisit this season of M101 since my prior visit to this curiously offset-core galaxy did not note much and I hope to revisit it again this season.

Something else that seems a good challenge to the WSW of M101 was Ugc8837. I wonder if anybody here has managed to observe this faint surface brightness object with a 20" or less in good skies?

Having before observed the brightest area of the Pegasus Dwarf, Ugc12613, I should think that an observation of Ugc8837 is within reach if I can believe the intensity as seen in MegaStar DSS overlays as being on the same scale. I will note that Pegasus Dwarf was a tough observation in my 18" scope but I had felt it was a solid observation but only of the brightest area of that dwarf.

Lastly, is Ugc12613 perhaps also a dwarf in our group?

[Ivan Maly]

The Pegasus Dwarf, UGC 12613, known also as DDO 216, is discussed at length by van den Bergh in his book The Galaxies of the Local Group. He concludes by saying that it "might be either an outlying member of the M31 subgroup or a free-floating member of the Local Group". I failed to see it with my 16", but I attempted that observation without preparation and did not persevere. I have only seen NGC 5474 with my 4" (f/5.5 Televue) and also intend to reobserve it with a larger aperture.

[Marko]

Thanks Ivan, interesting info on that dwarf.

I remain curious as to observations of Ugc8837 in 20" or less and also question that it may be a local group dwarf due to it's large apparent size and typical look of some of our dwarfs.

[Marko]

Last night at a site reaching 21.65 in the best part of the night I had made an observation of Ugc8837 and so my question on it being possible in an 18" is answered. It is close to the limits in my f/3.7 1944mm (paracorr) with the 8mm delos offering a bit better view than the 6mm Delos, most likely from larger exit pupil. I have not been able to identify this object as being 'special' in terms of perhaps being a dwarf of our local group so I suspect it is just a curiosity being an very low surface brightness 'challange' object for an 18" range scope. Steve Gottlieb brought it up in his 24" and it was of course more apparent there but still quite faint. it was a rewarding observation as far as I'm concerned.

[Steve Gottlieb]

Marko, I was just looking into UGC 8837 and realized this is one of the 9 Holmberg galaxies (Holmberg IV). It was discovered back in 1950 by Eric Holmberg during a survey of dwarf galaxies in the M81 group, so precedes the UGC/MCG/CGCG. Actually, it is now considered a likely member of the M101 group (http://www.atlasoftheuniverse.com/galgrps/m101.html). It's also included in the David Dunlop Observatory catalogue of dwarf galaxies (DDO 185).

As the Holmberg galaxies are generally pretty challenging (like Holmberg IX next to M81), I'd say this was a special find!

[Marko]

Thanks Steve. It did appear 'dwarf-ish' but just not of our own galaxy it would seem. So this adds then to my Feb 2013 observation of Holmberg II inspired by your piece in March 2013 S&T. Holmberg II was far easier to detect but it's challenge was picking out the slightly brighter areas. It was enjoyable to detect UGC8837 with the nice clean mirror on my 18" using my fairly new 8mm Delos (which I am really liking as a nice eyepiece for the deep stuff). It was also fun to share and discuss it with a group of other observers who also enjoyed the challenge at this one's rather low surface brightness. Thanks again for the view in your 24" as well.

[Clear Skies]

NGC5474 was not as spectacular as I expected it to be on the morning of 7 April. An even glow without use of AV and only subtly brighter on the NNW side with use of AV. Holmberg IV avoided detection in my 12".

Thanks, I now have glowing hot aperture fever...

[Marko]

Here are my notes from Ugc8837 and Ngc5474 so as to be complete on this thread.

Sqm generally around 21.5 up to 21.65 with 6.6 NELM or better, variable tranparency
Transparency 3-5/5 with seeing 4/5. Double-double split later but not ideally.
Temperatures were nice with only light sweatshirt required for quite a bit till later.

Equipment: 18" f/3.7 StarMaster with a freshly cleaned mirror using mostly 6mm Delos (324x) and 8mm Delos (243x)

con: UMa cmt1: NearM101_offsetCoreGalaxy:
NGC 5474 UGC 9013 CGCG 272-23 MCG +9-23-32 PGC 50216
MltG 11.3b 4.7x 4.7' -- S(c) RC3 14 05 01.6 +53 39 38
12:00am 6mmD 324x Full glow 1/6fov [2.2'] Core is far to the left [N} very near left and not over the center at all. The close to core FStar [NE of core GSC 3852:764] is down to left from core at 8:00. A distinct bright area is down and to right [SSE] near edge of glow. Another less obvious brightening is at far right edge [S], 1/6fov from core [2.2'] , has a slight brighter area perhaps elongated slightly vertical. A non-stellar spot of brightness is seen close to the upper right of the core [SW] appearing almost as a small extension poking out of the upper right of the core but this nub is only detected from time to time. A slightly darker area of size similar to the core was noted to the right of the core [S] and then the dim surface brightness picks up again to the right of this dip in the brightness. My limiting field star is 1/5fov up and to left of core [2MASS 14044295+5338335 at 15.2] but transparency is variable tonight.

con UMa cmt1: M101Dwarf_HolmbergIV:
UGC 8837 CGCG 272-13 MCG +9-23-17 DDO 185 Anon 1352+54 PGC 49448
Glxy 13.8b 4.8x 1.3' 18 IB(s)m sp RC3 13 54 44.7 +53 54 07
12:30am 8mmD 243x 2.7' length 2.5EL Length is about same length as the ultra thin triangle below it. With movement this can be held almost 100% of the time. The slightly brighter blotch in lower left of the galaxy seen on the DSS was not to be claimed in my 18" but it appeared available for a brief glimpse in Steves 24" although an attempt to confirm 5 minutes later failed to find this small knot (transparency was comming and going this night). Was able to view the galaxy in 6mm Delos but the 8mm view was more apparent so the 6mm view was at my visual limits for this diffuse glow. This dwarf galaxy which Steve Gottlieb identified as HolmbergIV and a member of the M101 group can be starhopped to easily from M101.

[Howard B]

I had a look at 5474 on May 8 under a surprisingly dark sky in the Oregon Coast Range mountains an hour drive west of Portland. Ordinary SQM at this site range from 21.0 to 21.3, but on May 8 we were fortunate to enjoy a 21.52 night. The seeing was below par, but darkness and transparency were excellent.

My notes read:
"Terrific view! Lot's of detail in this unusual galaxy near M101. The way off-center core is brightest along its lower (south) edge, with what looks like a dark lane curling right underneath it, ala M64. The faint, triangular shaped fantail below the core has a broadly brighter edge with a slight protrusion directly below and vaguely extending towards the core. 408x but 253x best."

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I suspect that under dark and steady skies that some of the HII regions would be visible. The brightest on on the northern edge has a spiral shape - hey Jimi, can you see it?

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[Jimi Lowrey]

Howard,

I looked at NGC 5474 this AM under less than ideal conditions there was a 10 knot wind blowing down the tube and you know what that dose to the seeing. I did however catch 3 H II knots in the galaxy. I will try on a better night and mark the ones I see and post it. I have not looked at this strange galaxy in a long time cool object.

[Jason Adamik]

Howard,

I looked at NGC 5474 this AM under less than ideal conditions there was a 10 knot wind blowing down the tube and you know what that dose to the seeing. I did however catch 3 H II knots in the galaxy. I will try on a better night and mark the ones I see and post it. I have not looked at this strange galaxy in a long time cool object.

Jimi, this has been one of my very favorite galaxies ever since 'discovering' it with a homemade six inch f/8 dob with an Excellent Parks mirror. This was in Davis Mountains Resort near you in 1995. The sky must have been incredibly dark, because this galaxy was Very bright, large, and obvious in spite of the low surface brightness. I'd be very interested in actually seeing detail within this rather peculiar galaxy. See you at TSP next Monday afternoon!

[Bertrand Laville]

Hi All,

Here is my observation of this galaxy, under a good but not exceptionally sky (SQM 21.69, SQMLZ 21.77)
I was not able to see any HII regions; only one star on the halo.
report here: http://www.deepsky-drawings.com/ngc-5474/dsdlang/fr

Clear skies
Bertrand
http://www.deepsky-drawings.com

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