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Observations of NGC 4449's Super Star Cluster?

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#1 SNH

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Posted 14 March 2019 - 04:34 PM

In last March’s issue of Sky & Telescope, Richard Jakiel wrote an article titled “Star Factories”. In it he writes about NGC 4449 (one of my few truly favorite galaxies!) saying, “At 10th magnitude and measuring 6′ × 4′, NGC 4449 is an easy object to observe and image with relatively small telescopes. A good 8- to 10-inch scope will reveal several bright condensations along the central axis, while larger instruments will make the galaxy “come alive” with numerous knots and dark rifts. Several SSCs [super star clusters] are also in the range of 16-inch or larger scopes, including a 15th-magnitude cluster in the core of the galaxy.”
The paper that first reported the discovery of those “SSCs” was published in 2001 by Gelatt et al. and titled The Star Clusters in the Irregular Galaxy NGC 4449. In it they write, “When one looks at the visible images of NGC 4449, an object in the center of the galaxy stands out because of both its brightness and its size. Its brightness suggests that it could be one of these super star clusters. Alternatively, it has informally been referred to by one of us as the nucleus of NGC 4449, but since Im galaxies do not have nuclei, this would be highly unusual. Here we are using the term “nucleus” to mean a centrally concentrated substructure of the galaxy that has been an integral part of the galaxy from the galaxy’s formation. One of our goals in this study was to determine the nature of the central object. One important piece of information is its age: a nucleus, by our definition, must be old; a star cluster that just happened to form near the center need not be old.”
I’ve been studying NGC 4449 (Caldwell 21) a little bit this spring with my vintage 10-inch SCT at 322x and am starting to wonder – am I actually seeing the SSC identified in the paper as “Cluster 1” - now [GHG2001] 1? I know that I’ve seen the middle of the galaxy as the brightest part of it and elongated. But I haven’t tried hard enough to confirm yet whether I’ve also been seeing the “small, intense “nucleus”” (to quote Steve Gottlieb’s notes) that is “Cluster 1.” I think I might be because I believe I’ve seen something “stellar” peaking out and it's listed in SIMBAD as magnitude +15.46.
So I’m curious to hear if anybody else feels they’ve seen it. And I’d love to hear how many of its numerous H-II regions you all have seen. I’ve seen several and am currently trying to see if its brightest – known as [HK83] NGC 4449 15 – is visible in my telescope stopped down to 3-inches. I know O’Meara saw it with his 4-inch reflector because he drew that and several others in his book Deep-Sky Companions: The Caldwell Objects.

 

Scott

 

EDIT: It seems that the one spot I label "11" has a paper on it titled AN EMERGING WOLF–RAYET MASSIVE STAR CLUSTER IN NGC 4449. Will have to read it.

 

NGC 4449 Thomas.JPG


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#2 uwe_glahn

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Posted 14 March 2019 - 05:12 PM

With 6-inch I could definitely catch two "nuclei", so I guess it is possible for you with the vintage 10-inch. I also got a brighter center with 4-inch and I think it is the brightening of the two central cluster.

 

sketches: 4", 88x; 6", 175x; NELM 6m5+, Seeing III

NGC4449_4_6.jpg

 

Things changed with 16-inch. Perhaps one of the most spectacular galaxies in the sky, especially for mid size telesopes.

 

sketch: 16", 360x, NELM 7m0+, Seeing III

NGC4449.jpg


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#3 IVM

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Posted 14 March 2019 - 06:54 PM

Here it is with 12", 125-375x, under 21.6 mag/arcsec2 skies. I am a bit unsure which spot in this relatively quick old sketch is "cluster 1", but if it's supposed to be the brightest, then it should be represented by the sharp center in the S part of the central spot, and certainly accessible in 10 inches. It can be noted that William Herschel described "3 or 4 bright nuclei" in this galaxy.

 

2014-03-31+NGC+4449.jpg


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#4 Redbetter

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Posted 15 March 2019 - 12:09 AM

When I observed it last year, I only made a tiny very rough sketch.  I had not scouted it ahead of time, so I wasn't prepared for the level of structure shown.  My notes reflect that, "looks like some of some sort of interacting galaxy, appears to have core and spiral structure on one end" while my sketch shows both ends of the brighter regions and a couple of stars down to about 17 mag immediately around/within the galaxy.

 

Barred irregulars like this sometimes have some brighter central clumps as well as something vaguely resembling a hooked spiral arm (like scythe) on each end, but often not very symmetrical or balanced.  Barnard's galaxy lacks large bright central regions, instead having a thick but diffuse central bar, with faint extension away on one end, while the other end is populated by a series of bright clusters & nebulae.



#5 bertandlaville

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Posted 15 March 2019 - 06:08 AM

Hi All,

 

I had the occasion, some years ago to observe deeply this extraordinary galaxy.

Here is my study, with a 25", in a good sky.

X520 Ethos 6mm

It is best to analyze the HII regions; some are highly concentrated, some are almost stellar. The two most important are CM 16 and 39 of the giant HII regions; Total I could highlight two giant HII regions, 12 HII regions, six star clusters, including one great heap in the center of the galaxy.

Details here: http://www.deepsky-d...4449/dsdlang/fr

 

Clear skies

Bertrand

 

NGC-4449-T635-BL-2012-02-18-1.jpg

 

 

 NGC-4449-HST-CM69-BL - Edited.jpg


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#6 Araguaia

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Posted 15 March 2019 - 06:13 AM

Thanks for the report.  I will try to observe it at 2 AM tonight if the sky is clear.  It will rise to about 30 degrees only - I wonder what I can see.



#7 herschelobjects

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Posted 15 March 2019 - 07:36 AM

My observation from my Bortle 4-ish backyard...

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  • N4449BV.jpg

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#8 SNH

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Posted 09 April 2019 - 04:33 PM

Well, I did get out over a week ago and was able to confirm that I can see the "super star cluster" at its center with as low as 153x in my 10" SCT. So that is pretty cool! Thanks guys.

 

Scott


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