Type | Galaxy |
---|---|
Magnitude | 11.9 |
Size | 1.883' x 0.866' @ 140° |
Right Ascension | 3h 40' 56.9" (2000) |
Declination | 22° 33' 52" S |
Constellation | Eridanus |
Description | pB, S, lE, pglbM, * sf |
Classification | Sa |
Harold Corwin
IC 1983 is probably identical with NGC 1415. The NGC object is the brightest galaxy in the area, so is the one most likely to have been seen by Swift. He has his usual poor position (10 seconds and 3 arcmin off the correct position) as well as a sketchy description, "vF, pS, R; not [NGC] 1426" in his big 11th list in AN.
The name of the galaxy that Swift was pretty sure this was not is not in the IC description. Just as well; it is a distraction at best, an embarrassment at worst as it is over half a degree away from NGC 1415. But it does lead us to a question: Could Swift have meant N1416 rather than N1426? N1416 actually is "vF, pS, R", while N1415 is much brighter (but see the discussion below!). However, N1416 has two bright stars just south pointing at it -- had Swift seen these, he surely would mentioned them, just as he did dozens of other asterisms near his nebulae.
I think this is unlikely as N1416 was found by Muller in the mid-1880s with a 26-inch refractor, and has no GC number (see NGC 1416 for more on its chequered past). In Swift's original paper, the first list of nebulae found at Lowe Observatory, IC 1983 appears as the 20th entry. There, Swift's description reads "vF, pS, R. Not G.C. 765". GC 765 is indeed NGC 1426, so Swift has got the right NGC number for the AN paper.
Unfortunately, this means that he overlooked NGC 1415 and 1416 altogether when he was putting his list together. Somehow, Dreyer missed the possible NGC identifications, too.
Whatever happened, I think that NGC 1415 is the best candidate for Swift's galaxy.
Corresponding with Gary Kronk in April 2017, I found that he is more inclined to the NGC 1416 identification because of Swift's description of IC 1983 as "vF, pS, R". I am sticking with my argument above, and would also cite the position differences, too. Swift puts IC 1983 at roughly the RA of NGC 1416 and the Dec of NGC 1415 -- but it ends up considerably closer to NGC 1415.
I also note the southerly declination; many of Swift's southerly objects seen from Mt. Lowe have descriptions that make them seem too faint for their apparent magnitudes. Examples include IC 5237 = NGC 7361, IC 5269, IC 5273, and IC 5328. He calls all of these "vF" or "eeeF", yet all are Shapley-Ames galaxies and have total visual magnitudes between 11.4 and 12.4. With a total magnitude of 11.6, NGC 1415 is probably another such case. For the record, NGC 1416 is at V_T = 12.9 and has a considerably lower surface brightness as well.
Gary accepted NGC 1415 for his book on Swift. He does mention the problem with Swift's description of IC 1983 as "R[ound]", but given that Steve Gottlieb, Wolfgang Steinicke, and I all chose NGC 1415, Gary finally went with that galaxy.― IC Notes by Harold Corwin
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