Harold Corwin

IC 5179 = IC 5183 = IC 5184. As with IC 5003 and its synonyms (which see), Swift swept up this galaxy on three different nights in the summer of 1897, his last full summer of searching for nebulae. One of those nights, 26 July, is, perhaps not coincidentally, one of the nights on which he saw IC 5003.

He picked up this galaxy first on 19 July, giving it a position of 22 15 28, -36 52.5 (precessed to J2000.0) and describing it as "pF, pS, lE, bet 2 sts in meridian, 8 1/2m * sp, np of 2". The "sf" is IC 5186, which also see. I immediately suspected problems since he placed IC 5186 at 22 16 18, -36 50.5 for J2000.0, north following, not south as Swift states. There is nothing at his position for IC 5184 (as this observation eventually became).

On 26 July, he found a nebula at 22 13 19, -36 52.7 (J2000). This one he described as "vF, L, R, * close S, B * sp". Finally, on the 20th of September, he has another nebula at 22 15 21, -35 50.6 (J2000): "pB, C, [sic] S, F * in contact sf, sev pB sts form segment of large circle." These became IC 5184 and IC 5179; like IC 5183, there is nothing at Swift's position.

However, at 22 16 09, -36 50.6 (J2000), is a large, bright galaxy between two stars almost on a north-south line with it, with a brighter star to the southwest, and inside a nearly complete circle of stars. While Swift mentions only some of the stars in each description, it's clear that the galaxy can match all of his descriptions with very little forcing.

The positions are typical of his last year or two of observing: full of large accidental errors, and also filled with digit errors. By this time, Swift was 77 years old, and I suspect he was getting tired of trekking up and down his observing ladder to read the setting circles of his 16-inch refractor. It's also possible that his eyesight was beginning to fail, too. We know from the obituaries that he did go blind in his old age.

In any event, the positions can all be more or less reconciled with the true position of the galaxy with digit errors, though a large helping of random error is needed here and there, too.

The galaxy itself is a fairly large and bright one, somehow missed by John Herschel during his southern sweeps from the Cape of Good Hope. The central region is knotty and complex, not well-seen on the DSS images. NED has two convincing images that show the nucleus clearly: one from 2MASS, and the other from the Carnegie Atlas (from a Las Campanas 2.5-meter plate) which shows an unresolved, essentially stellar nucleus. I've taken the brightest infrared source from the 2MASS PSC as the nucleus.

What about IC 5186, "south-following of two"? Briefly, it looks like Swift's RA is 2m 35s out, but the galaxy can be recovered by his description of the star field around it. See its story just below.

― IC Notes by Harold Corwin

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