Object of the Week February 28th 2021 - NGC2537 The Bear's Paw Galaxy

Arp 6
UGC 4274
PGC 23040
Mrk 86

Galaxy

Constellation: Lynx

RA: 08 13 14.5
DEC: +45 59 31

Type SB(s)m pec
Mag: 11.7
Size: 1.9' x 1.7'

Lying across the border from the Bears Toes in Lynx is the Bear Paw Galaxy, NGC2537. NGC2537 is a rather "peculiar" barred spiral - pun intended BTW - in that I have yet to wrap my head around how this galaxy, speaking strictly from a visual POV, is classified as a barred spiral galaxy. But more on that later.

Located in Lynx at an approximate distance of 25Mly, NGC 2537 was discovered by William Herschel using his 18.7" speculum mirrored telescope in 1788. Herschel himself described it as "approaching planetary" in appearance, no doubt alluding to its nearly circular appearance. One source I found claimed that NGC 2537 was originally classified as a globular by Dreyer, again owing to its round, circular appearance. Today, in larger more modern scopes, NGC 2537 proves to be much more unique in appearance that Halton Arp recognized it as such and labeled it #6 in his catalog of Peculiar Galaxies.

Although classified in the RC3 as a barred spiral galaxy owing to what astronomers believed was a single, detached arm that wraps 180 degrees around an ill-defined core, NGC2537 has also been identified as a BCD, or a Blue Compact Dwarf or even compact irregular in some literature. BCD's typically comprise of young irregular or lenticular galaxies. Comprised of very little gas or dust, BCDs primary stellar makeup is that of young, blue energetic stars which gives BCD's their typical blue appearance. Some other characteristics of BCD's include but not limited to:

• Small in size. Some are less than a 10^th the size of our own Milky Way
• Faint
• Low in metal content with very little dust or gas in its overall composition
• They appear blue in color
• High in starburst activity
• Many are involved in galactic mergers

But, one common aspect of all BCD?s is their lack of uniform shape IE they are typically irregular. Visually speaking, I would agree with that claim but take that with a huge grain of salt as I know not of what I speak! :P Visually, and to briefly circle back to the end of paragraph 1, the reason I feel the way I do is that when I look at the Bears Paw, it doesn't, in anyway, resemble what we've come to expect in a barred spiral. Barred spirals such as NGC 2500, NGC 2523 or NGC 1300 are ubiquitous examples of spiral galaxies exhibiting a bar structure with sweeping spiral structure. I just don?t see one in NGC 2537 no matter how hard I look.

NGC2537 was spotted by our own Sue French in her 5.1" refractor. In her book Deep-Sky Wonders she writes that Arp 6 shows 'a bright, core that exhibits odd, large-scale patchiness'. In her 14.5" scope she starts to see "3 lumps", or the "toes" of the Bears Paw. Although I have observed this object many times, I myself have only two, albeit not very descriptive, annotated observations. One with my 25" and the other with the 48".

Feb 20^th 2010 Green River SP "S4/10 T7/10 315x Bears Paw. Lynx. Defined round shape. The 3 toes are apparent. Little mottling."
March 24^th, 2012 Ft Davis TX "21.7SQM 488x Looks great! Defined dark lanes show the claws well. 15.3mag NGC 2537A visible due south of 2437"

Which brings us to two great extras for this OOTW - NGC2537A and IC2233.

NGC2537A or more appropriately titled PGC23057, a smaller and fainter spiral galaxy 4.5' E of 2537. This spiral makes for an interesting object as it lies nearly 500Mly beyond 2527. The other, IC2233, is a beautiful superthin 17' south/southeast of 2537. Jimi covered IC2233 as an OOTW 6 years ago in this post, so please check it out.

Please consider NGC2537 the next time you're out observing. It isn't particularly difficult and it provides a beautiful view that actually looks like its namesake. And how fitting is it that this object lies just off the "toes" of the Big Bear!

And as always,
Give it a go and let us know!

Attachment 4221

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Attachment 4223
copyright: Naoyuki Kurita

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Ok. Just a quick OT response. I've seen it in other posts and I'm now seeing in this one. Formatting of certain characters isn't rendering properly. Parenthesis, quotes, hyphens, copyright symbols etc.

We are aware and will look into this immediately.

EDIT: A little progress. By compiling in MS Word, and copying and pasting my post to DSF, it incurs these errors. I was able to go back and remove the errors. If you draft in word and then copy and paste into DSF, you may see these same formatting errors. You will have to go back after posting and change the errors in DSF. After saving your edits, your errors will be fixed.

We will continue looking for a fix. This is just a quick dirty workaround.

We apologize for the inconvenience.

Hi here's my observation from 3/11/2010: Ngc 2537 aka Bear Paw galaxy in Lynx; magnitude: 11.7 ; size: 1.9'x1.7' ; roundish ; resembles a planetary nebula; mottling around the periphery gives the appearance of a bears paw : 3 bright knots observed: I used a 7mm Nagler at 275x with my14.5 Starstructure Dob f/4.3

Attachment 4224

I dont have an observation for Ngc 2537A, but do have a sketch for IC 2233 : one of the thinnest galaxies I have observed ,I used a8mm Ethos at 198x

Attachment 4225

According to Wolfgang Steinicke, the nickname of this remarkable galaxy came from University of Alabama astronomer Ron Buta. He observed (and sketched) a number of galaxies in the 1970s at McDonald Observatory. Through a 36-inch, he described the galaxy as

"Small and of relatively high surface brightness; shaped like a bear-paw, the structure consisting of a single spiral arm winding from W to E around the N side; this ring-tail includes 3 knots, one of about 15 mag; a bar-like feature shows in the interior region of the arm and extends to the S edge of the galaxy; there is a faint glow between the arm and the bar feature".

with sketch...

Attachment 4226

Hi all,

NGC 2537: With a 10", I didn't see the bear paw that I dint know.
IC 2233: The galaxy is seen as a very thin and very weak blade, 2.5 ′ long, practically without thickness.
Here is an old sketch of the field.
The report is here: http://www.deepsky-drawings.com/ngc-...233/dsdlang/fr

Clear sky
Bertrand

Attachment 4227

The most detailed observation I logged for this beauty was in April 2015 under dark skies in the French Alps. 14" SCT @168x / 29':

Not very bright but with notable structure that is clearly visible with AV. There is a dark patch north of the middle. Sometimes the dark parts to the east and west of the middle, that run from north to south, can be distinguished because the central, elongated part stands out. Surrounding the brighter central part a brighter arc is subtly visible, from east to west via the north, that does not continue in the south. Structure is clearly visible. On the NW edge is a bright, almost stellar knot, the HII region Markarian 86B.
To the ENE is a mag. 14.5 star, 2 1/2 times that distance to the ESE is a mag. 11 star, 1/4 FoV to the WNW is a white-yellow mag. 8 star (SAO42225).

In 2011 under Dutch skies in my 12" SCT I was not able to make out such detail, 179x / 27':

Quite a large, round patch with subtly ragged structure. Close to the NE is a mag. 10 star, slightly closer to the NE is a mag. 14 star that is at the limit of visibility, 1/3 to the WNW is a pale white mag. 8 star.

Attachment 4228 Attachment 4229 Attachment 4230

I can contribute a 16" drawing from 2016. NGC 2537 is a beautiful galaxy with lots of details even in a 16". NGC 2537A was visible but faint and detailless. Nearby IC 2233 was amazing as well.
16", 220x (8 mm Planetary)
Attachment 4231

NGC-2537: 2004, 272x, 20" f5: "A re-visit from 1990. Can see large globs of mottling this time." 1990, 130x, 13" f5.17: "Nice, solid, round glow."
NGC-2537A: same night as above: "Averted vision scale #1; small and round."
IC-2233: 2011, 318x, 20" f5: "Can see it with direct vision and no filter PA~160 [actually 183 ]

My most recent observation is from 2010 (!) which tells me I'm overdue for another observation. Here's what I saw eleven years ago with the 28-inch:

"...a terrific view of the Bear Paw galaxy in much steadier seeing! A big bonus is the long and very thin edge-on galaxy IC 2233. But the Bear Paw is the main attraction with its distinctive 3 lobes shaped much like a paw print - maybe a 3-toed sloth would be more accurate as a comparison as I think bears have more than three toes.

Attachment 4232 Attachment 4233

Anyway, the toes showed several brightenings of star-forming regions and perhaps a superimposed field star or two. NGC 2357A is a bit of galactic fuzz to the left (east) of the Bear Paw in my sketch. A terrific view altogether! 408x, 21.15 SQM."

Here are better versions of my Bear Paw sketch:

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Found some entries in my logbook between 16-inch and 27-inch. While the paws were difficult but doable in the 16-inch, the 27-inch shows bright detail, especially the bright spot in the NW.

sketch: 20", 350x, NELM 6m5+
Attachment 4236
home

The only log of it that I have goes back 10 years with my 12.5”. I’ll definitely need to revisit.

Feb 22/11. 12.5” @304X. Small, fairly bright, irregularly (scalloped) round.

No note made of either of the other galaxies.

Bill

This is what I picked up in my 22" a while ago (copied from my Arp book). I don't remember when I observed it, just need to find my logbook. It was before 2007 though.

Attachment 4239
22" @ 327x
field: 5.5'
Seeing 7/10
Transparency: 8/10
NELM: 6.8

From a 12.5" observation over a decade ago:
"like bear print in sand, roundish, large, resembles a planetary, no obvious central core, clumpy, face on?, nice easy object--add to favorites"
SQM not noted, but likely around 21.5 due to the date.

I don't have sketches to contribute, but just wanted to remark that BCDs should have gas fraction and star formation rates on the order of giant spirals. This starburst activity should be fueled by something. Some even refer to BCDs as gas-rich (Zhao et al. 2012).

Hello Dragan,

I observed this galaxy with my 12" Dobsonian last year. At 275x magnification I saw two brighter sections at the W and E sides and another brighter section in the center.

Clear skies

Robin

Attachment 4260
The only traceable log I can find is from 2012 March, an observation with John Tatarchuk's 25" scope from central Texas. This one's going back on my wishlist for sure.

Clear Skies
Akarsh

Attachment 4692
Inspired by this OOTW, I got myself to look at this object again earlier this year in February with my 18". This was at Pinnacles National Park, California, west entrance. The conditions were terrible. The transparency was bad with clouds coming in later during the night, the sky was bright, but the seeing was okay.

My logs read:
"First look like an unfiltered PN. Mottling visible throughout the edge in the form of knots. Occasionally see all three spikes. Confirmed orientations of spikes against POSS after first calling it out at the eyepiece. Not as nice or easy as expected, but such are the skies."

Here's my contribution with a 16" from earlier this year. The first impression gives a bright, slightly oval galaxy with a bright knot on the NW rim. Increasing the magnification is rewarding: the galaxy starts to “glow” and the mottling is very apparent now. The horseshoe shaped ring is seen, composed of several brighter areas within the galaxy and vaguely the middle toe of the paw can be discerned as well. On the N rim a m15 star is visible with AV.

Attachment 4695

Martijn