Harold Corwin

NGC 4019 = IC 755. Though John Herschel's position is 2 min 16 sec and 6 arcmin off the true position of IC 755, the IC object is the only galaxy in the area to have a 9th magnitude star 5 arcmin southeast, matching John Herschel's note. Other possibilities include NGC 3996 (but seen in the same sweep as N4019), NGC 4037 (this has an 8th magnitude star following by 6-7 arcmin, but the star is a bit north, not south), and CGCG 069-010 (but that has a pretty low surface brightness and no bright star near).

There is nothing at John Herschel's position, so I'm pretty sure that IC 755 is the correct object. Malcolm notes, however, that there is a 9th magnitude star southeast of John Herschel's (empty) position. This throws a little doubt on the IC 755 identity, but requires that John Herschel's object be a comet. This is a possibility, but I think that the equality with IC 755 is more likely.

Using JPL's "Small Body Identifier", I found that Comet 55/P Tempel-Tuttle was about five degrees north of John Herschel's position on the date of his observation of NGC 4019. However, its predicted nuclear magnitude was 23.5. That, and the position offset effectively rules it out as John Herschel's object.

Checking the sweep (419 on 23 April 1832), I see that the RA is not only marked with a colon, but that John Herschel thought he was observing H III 3 = NGC 4028. The position measurement is one of those that John Herschel referred to a previous measure, in this case a star with a clock, beat, and wire listed (11 51 45, -19, leaving the field), but no NPD index. NGC 4019 has "-19" for the clock, "-38" for the beat, "X" (leaving the field) for the wire, and "2 41 50" for the NPD index. The nearest star in the sweep is [beta] Leonis at "11 40 35", "-15", "1", and "2 19 36". Re-reducing John Herschel's observation yeilds a position with the RA two minutes larger than John Herschel's published value. This brings John Herschel's object to within 20 seconds of time of the position of IC 755, so makes it even more likely that the IC object is also John Herschel's.

The object itself is a patchy spindle, and many of the positions collected in the main table are for knots southeast of the center of the galaxy. The Pan-STARRS1 position that I chosen is very close to the center of the faint bulge of the galaxy (best seen in the SDSS color image). My own estimate from the SDSS, and the two 2MASS positions are close, also. The nucleus is probably hidden behind the intervening dust, gas, and star clouds. A radio observation might find the nucleus for us.

― NGC Notes by Harold Corwin

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