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.
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.