NGC 6174

History and Accurate Positions for the NGC/IC Objects (Corwin 2004)

NGC 6174 is one of three nebulae found by Lord Rosse in 1849 while he was observing NGC 6173 (h 1962 = H III 640), and is the only one of the three included in the GC and NGC. JH took the observation from LdR's 1861 paper which lists only the three nebulae in the area found by JH, plus a terse comment "Another nearby." LdR's 1880 monograph has a fuller description of the observations, as well as a sketch of three of the nebulae. While the sketch is not labeled, it is clear from the descriptions that the one shown in the upper left is NGC 6173. A double nebula is directly north at a distance, estimated in the sketch, of 6 arcmin; while the third is an estimated 8 arcmin "east" of the second. The direction is in quotes since the diagram does not fit the sky unless LdR (or Dreyer, who prepared the monograph) got the direction wrong. Normally, the arrows in the diagrams point to the east; in this case, it must be west. LdR has another observation and sketch in 1851 which confirms the three sketched in 1849.

The fourth nebula is "About 15 arcmin following and 3 arcmin north of this [N6173] there is a new neb, vF, gbM." There are no galaxies in that location that LdR might have seen -- but there is one 15 arcmin preceding and 3 arcmin north that fits his description. This is another indication that the east/west directions in this observation have been reversed.

Dreyer added a note to the NGC: "Second of 3, forming a rectangular triangle, the 2 others being assumed to be h1962 [N6173] and h1963 [N6175], but the identity of the group is doubtful." Dreyer's note is incorrect in making two of the nebulae identical to JH's; only one is. The other two are "novae."

LdR's final observation from 1860 suggests that he saw N6175 ("... an E neb, with a * close to f end, and either a knot or a * in p end"), but then concludes, "Found no other nebulae near. Twilight troublesome." Perhaps the last two words explain the lack of additional nebulae, though N6175 is in the midst of a cloud of rather faint galaxies in the outskirts of Abell 2199.

So, we have a problem: three new nebulae found by LdR, but only one NGC number for them. Several sources have taken the double nebula north of N6173 as N6174. I am reluctant to do this as Dreyer called N6174 only "vF" making no mention of the duplicity. Of the two nebulae north and west of N6173, I favor calling the brightest of these (which is also the closest to N6173) N6174. LdR observed and sketched this twice, whereas he has only one observation of the other.

Published comments

Sulentic & Tifft (1973)

The RNGC (Sulentic and Tifft 1973) notes that this is a 15.0 mag galaxy. Their coded description reads E,R,BM,ALMSTEL.