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NGC 6607

NGC 6607, LEDA 61550, MCG+10-26-023

RA: 18h 12m 14.7s
Dec: +61° 19′ 58″

Con: Draco
Ch: MSA:1079, U2:30, SA:3

Ref: SIMBAD

(reference key)

Type: galaxy

Mag: B=15, V=?

Size: 0.562′ x 0.457′
PA: 37°

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

NGC 6607, 6608, and 6609. This is a trio of objects all credited to Lewis Swift. They were all discovered on the night of 4 Aug 1883, and are listed in Swift's first paper as being the 5th, 6th, and 7th of 8, respectively (numbers 91-93 in his sequential numbering of the entire list). The other five objects are N6592, N6594, N6597, N6601, and N6617. Though Swift's positions aren't too good for these five, either, the galaxies are nevertheless unambiously identified by Swift's comments about nearby stars (or the lack of them). N6601, by the way, is the only other object of the eight that Swift found that night in 1883; the remaining four are dated 14 June 1885.

Swift's declination for NGC 6608 is the problem. He places it at exactly the same declination as NGC 6609 just 15 arcsec north of NGC 6607. So, while there are three galaxies in the area, only two are at Swift's declination while the other is 2 arcmin south. Furthermore, the southern object is a faint edgewise Scd or Sd with a low mean surface brightness. Not only does it not match Swift's descriptions of shape ("R", "R", and "lE" for the three objects) it is so faint (around V = 15.5 at a guess, compared to V = 14.5 and 15.0 for the other two) that I would be surprised if Swift could have seen it at all. The object that Swift described as the faintest of the batch of eight (NGC 6617, which see) is considerably brighter than than this spindle. In addition to that, Swift says there is a "vF star near" his object -- there are none near the spindle that he could have seen that are not nearer NGC 6609 (and that leads to yet another hypothesis for NGC 6608 ; see the last paragraph of this note).

Still, there are three galaxies here, and three NGC numbers. If we assume that Swift's RA's for the four objects found this night are correct among themselves in a relative sense, then we can apply the correction necessary to make his RA for NGC 6601 agree with the GSC position (+13 seconds of time) to the others. This leads to RA's for the others that are different from the true RA's by -4, -4, and -3 seconds of time, respectively. Thus, Swift's RA's for the three galaxies are in very good relative agreement.

So, in spite of my doubts that he saw the faint edgewise galaxy (MCG +10-26-024), I'm going to assume a 2 arcmin error in the declination for this object and call it NGC 6608. The other two, NGC 6607 and NGC 6609, fit his descriptions very well -- including the "F star near" NGC 6609 -- so there is no problem with them.

As a final possibility, I'm going to suggest that perhaps, just perhaps, Swift's observations of the latter two objects (numbers 92 and 93 in his list) refer to the same galaxy. Had the observations been made on different nights, I would have said "A-ha!" at the beginning of this story and equated them with hardly a doubt left. As is, we'd have to assume some sort of blunder in Swift's observations within a single night in a small area of sky. With that third galaxy just south, though -- well, Occam's razor slashes deeply enough that that is the more likely choice.

Published comments

Sulentic & Tifft (1973)

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

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