Harold Corwin

IC 864 and IC 866 are the northern-most two galaxies in a group of eight, seven with IC numbers from Swift and Javelle. Swift swept over the area in April of 1889, and Javelle followed in June of 1891. Javelle's positions are, of course, much better (but see IC 869 for a bit of a mystery), and there is little doubt as to which galaxies he saw.

Swift's positions, from his 8th list, are -- as is not uncommon -- not good enough to unambiguously identify the objects he found. Making the assumption that he saw the brightest five of the group, we can, however, make some pretty good guesses. His descriptions are no help; four of the five are simply "eeF, pS, R". For the last one, however, he adds a comment about "4 pB sts in a curve sf point to the 1st, 3rd, 4th, and 5th." There is indeed a curved line of four stars south of the group. Assuming that this curve continues on through the four galaxies he names -- with only the 2nd object off the curve -- we have another way to identify the objects. This leads us to the following identifications: List 8, number 68 is IC 864, L8N69 = IC 866, L8N70 = IC 867, L8N71 = IC 868, and L8N72 = IC 870. While these are not certain, they are reasonable given Swift's positions, the brightnesses of the galaxies, and the clue from the line of stars.

Some additional notes: IC 868 and IC 870 are pretty clearly the close pair of galaxies on the southern edge of the group. These are the 1st and 3rd brightest in the group. Also, Swift comments that his "4th of 5" is a double with the 5th. Next, if Swift's relative positions are at all indicative, the 4th brightest, IC 867, is pretty clearly the 3rd of his five.

This finally gets us to IC 864 and IC 866. Swift makes the relative positions just 2 arcmin apart in Dec; his RA is the same. However, on the sky, the 5th and 2nd brightest galaxies have nearly the same declination (only 4.3 arcsec different), but are separated in RA by just about 2 arcmin (1.94 arcmin to be exact). Perhaps Swift simply made a mistake in his observing notes or in his transcription of them. Whatever happened, these are the only two galaxies in the area that he might have seen, so we'll assume that he did indeed see them.

That being the case, we must move Swift's name off the IC entry for IC 869 and
put it on IC 864.

― IC Notes by Harold Corwin

Drawings, descriptions, and CCD photos are copyright Andrew Cooper unless otherwise noted, no usage without permission.

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