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I've just encountered (in an article about the detection of 2-methoxyethanol in interstellar space) references to an object called NGC 6334I. It seems that the object is a protostellar cluster.

When I Google "NGC 6334I," it turns up a few papers, like this and this, but these sources only use the name; they don't explain its construction.

Similarly, when I search for "NGC 6334I" in The Interactive NGC Catalog Online, it returns the entry for NGC 6334. So their search mechanism seems to strip off the trailing letter 'I', but my intuition tells me that these papers' authors would not have included the suffix if it weren't significant. To put it differently, I am not comfortable assuming that "6334" and "6334I" refer to the same object.

I've tried all sorts of Google searches to learn about the format (syntax) for the identifiers used in the NGC, but have turned up nothing.

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2 Answers 2

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It is arbitary, it is the Roman numeral for one.

The first five main regions that have been identified in the infrared received the names NGC 6334-I to NGC 6334-V (see Persi & Tapia 2008). https://arxiv.org/pdf/1911.06579.pdf

Large-scale surveys made at different wavelength ranges have identified these very young spots and, because not all of them emit in all wavebands, several name sets have been proposed and this has contributed to some confusion. In particular, Roman numbers I to V were assigned to the far-infrared peaks by McBreen et al. (1979) and letters A to F to the radio sources by Rodr´ıguez, Canto & Moran (1982). The nomenclature adopted here is an extension of Kraemer ´ and Jackson’s (1999, Appendix) identification scheme. https://www.aspbooks.org/publications/905/456.pdf

enter image description here

The 40-250 ¡im map of NGC 6334. The effective wavelength is 69 pm for a source temperature of 70 K. Roman numerals I-VI indicate the peak source positions. The contour unit is 7.5 X 10-17 W m~2 Hz-1 sr-1 . The locations of the other sources shown include: crosses, 40-350 pm peak source positions; dotted crosses, 1.95 cm continuum peak positions; diamonds, 6 cm continuum positions; triangles, H20 maser sources; squares, OH maser sources; star, 2-20 pm source; open squares, 1 mm continuum peak positions. In the lower right corner the beam size and chopper throw are shown. https://articles.adsabs.harvard.edu/pdf/1979ApJ...232L.183M

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    $\begingroup$ An interesting misinterpretation of $\mu$ from the scan-to-pdf there under the plot. Never seen that one before. $\endgroup$
    – Jon Custer
    Apr 23 at 21:17
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The Wikipedia page on NGC 6334 has a photo identifying NGC 6334I as a star-forming region or protocluster in the Cat's Paw Nebula. The reference to an ESO Newsletter from 2017 stated that "...this new image from ALMA shows a massive protostar, nestled deep within this dust-filled stellar nursery, that is undergoing an intense growth spurt, most likely triggered by an avalanche of gas falling onto its surface. This new material feeding it is causing the protostar to shine nearly 100 times brighter than before."

The newsletter does not reference a paper.

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