Anonymous Galaxies in the NGC 999-Group
In the german magazine Magellan (#4) Klaus Spruck and Frank Leiter (Heuchelheim) reported the visual "discovery" of 6 galaxies in the field of the NGC 999-group of galaxies, located in Andromeda. This prominent group consists of the bright galaxies NGC 995, 996, 999, 1000, 1001 and 1005. After scanning diverse catalogues they did'nt find any listing of the 6 "new" objects.
As I'm concerned with deep-sky data for many years (especially galaxies), I was excited to see what's going on here. I come to the conclusion: except of a short note (see discussion below) the galaxies are indead "anonymous". But this has changed, now they must called "Heuchelheim 1 thu 6", at least among german amateurs.
What's the reason for missing such bright objects (#1 has a visual magnitude of 15.5m)? For this, two questions must be answered: What did the visual observers of the NGC/IC saw in the field? Why are the objects not listed in the classical POSS-based catalogues?
Historic Visual Inspections of the Field (NGC, IC)
Up to the beginning of the last century catalogues of nonstellar objects were produced through compiling visual observations made with various instruments. The most prominent results are Messier's catalogue, the NGC and its Index Catalogue (IC), which contains also objects found on photographic plates (e.g. Max Wolf's discoveries). Beside of reliable data the results contain also very poor data or even identities between entries, due to different observers (e.g. NGC 1593 = NGC 1608 = IC 2077; further examples are here). Dreyer, the author of the NGC/IC, had a lot of trouble with this. Even today the NGC/IC is not "clean" at all, the NGC/IC project is still dealing with this problem. It's possible, that some of the "Heuchelheimer" are mentioned in the historic observing notes.
The bright NGC-galaxies were all discovered in 1876 by Stephan using a 80 cm-reflector. He might have seen the 6 objects! Perhaps the seeing was bad or the mirror was steamed up. But there is another observation of the field, this concerns IC 240, found in 1891 by Bigourdan with the 30 cm-refractor of Paris Observatory (#409 in his list). Unfortunately there is nothing at his position (see fig.). This is untypical for Bigourdan, his data are, compared with other observers, very reliable and precice. He corrected his data later: the position angle to his reference star was wrong. The real IC 240 is a chain of 4 stars, near to NGC 999 and Bigourdan states explicitely, that he was not confusing his object with NGC 999. It is interesting, that the UGC, CGC and PGC list the identity NGC 999 = IC 240, which shows, that known corrections are often ignored in the modern catalogues. This also shows that the work of the NGC/IC project is of great value for the analysis of present observations. To clear critical cases ("puzzles"), its often necessary to simulate the historical observation with a comparable aperture. Steve Gottlieb has done much in this field.
Field around NGC 996 (POSS II image; 12.5' x 12.5'). The galaxies H1, G, H3 and H4 form a chain. The cross marks Bigourdan's nominal position of IC 240. Actually IC 240 is a small chain of 4 stars NE of NGC 999 (R is Bigourdan's reference star).
Photographic Survey of the Field (POSS)
The 6 galaxies are all bright enough to be seen by the observes of the NGC/IC. Missing bright objects is normal, there a many similar cases in the sky. The NGC/IC is the result of uncoordinated sweeps made by many different people, the survey was far from beeing complete. Today the Palomar Observatory Sky Survey (POSS) shows all kind of objects, available to anyone - so, why to observe in cold nights? Another fact is: on the (blue) POSS many galaxies look fainter than they appear visually! This is due to the difference between photographic (B) and visual magnitude (V), which varies for galaxies between 0.5 und 1.1.
My research on the 6 anonymous galaxies (H1 thru H6) was not completely unsuccessful. Three galaxies are mentioned in the notes to Nilson's UGC: "chain of 4 galaxies betw U2123 and 2127" (IC 240 is not ment!). Now UGC 2123 = NGC 995, but unfortunately UGC 2127 = NGC 999. Because the chain exists between NGC 995 und 996 (see fig.), formed by H1, H3, H4 and a faint galaxy between H1 and H3, Nilson made a typo: one must read U2118 (=NGC 996) instead of U2127! Anyway, this is everday life, resulting from managing large amounts of data.