Proposed Nomenclature for Extragalactic Planetary Nebulae Q Parker

Proposed Nomenclature for Extragalactic Planetary Nebulae Q. Parker & A. Acker CDS/ULP/Macquarie/AAO Hopefully the most boring talk during the workshop! Extra-galactic PN workshop Garching May 2004 1

You know it makes sense… n n n The ability to identify and distinguish the diaspora of celestial objects benefits from application of a systematic and logical nomenclature. This often includes value-added information within the naming convention which can aid in placing the object positionally – either via an RA/DEC or l, b concatenation. The CDS has put in place a system for advising on the structure for such nomenclature and for its acceptance and implementation following IAU/UAI guidelines Extra-galactic PN workshop Garching May 2004 2

Extra-galactic PN workshop Garching May 2004 3

Everything is in place at CDS n A comprehensive web site already exists to assist the process…. Extra-galactic PN workshop Garching May 2004 4

The registration form is available on-line…. . Extra-galactic PN workshop Garching May 2004 5

Galactic PN n n n They use PN Glll, l+/-bb. b This is actually not sufficient even to discriminate amongst all the known galactic PN Especially true with the advent of MASH (Macquarie/AAO/Strasbourg H-alpha Planetary Nebula project) which has added ~1000 new Galactic PN some within an arcminute or so of each other PNGlll. k+/-bb. b. A, B, C etc was proposed in the `unlikely’ event of PNe being found in such close proximity…. This demonstrates the need to try to future proof such designations against use of too crude positional identifiers if positional info is used in the designation at all Extra-galactic PN workshop Garching May 2004 6

How you `officially’ enter a new nomenclature Extra-galactic PN workshop Garching May 2004 7

So what do we want to use? This is a good forum in which to decide… n n n Let’s look at the initial proposal applied to a galaxy in NGC 7793 for example PNGNGC 7793 J 2357499 -323520! This is quite a mouthful even if we replace NGC with N! It is probably still not enough to discriminate between PN in an external galaxy…. . We may need PNGNGC 7793 J 23574998 -3235206 if we are to use this system effectively Extra-galactic PN workshop Garching May 2004 8

What is in a name? n n n Are there any tractable alternatives? Clearly the host galaxy is a key parameter immediately placing the PNe in context Then we need to identify the object as a PN (or PN candidate) Then we need to discriminate it from all the other (perhaps hundreds or thousands) of PN that may be discovered in an individual galaxy. . Perhaps an RA/DEC concatenation is not the best way forward…. Extra-galactic PN workshop Garching May 2004 9

So what can we do? n n n For extragalactic PN actually residing in galaxies all the objects occur within quite a small region – a few tens of arcminutes for most Their individual positions will only be slightly different according to the majority of current such designations PNG – that moniker has been used for Galactic PN but the associated positional information has been l, b not RA/DEC so there is scope for confusion if we use PNG again… Extra-galactic PN workshop Garching May 2004 10

Things to consider n n Thousands of new PN being discovered in galaxies at greater and greater distance which are of smaller and smaller angular extent To discriminate between individual PN with a single identifier would require an extremely long indentifier if positional info is used to any effect Suggest that any identifier should be future proofed i. e. when we can find PNe within a hundredth of an arcsecond from another in a distant galaxy… Extra-galactic PN workshop Garching May 2004 11

Nos suggestion du jour n n n We simply use a running number in order of PN discovery epoch in a particular galaxy So we know that the greater the number the newer the discovery. . Also the largest number immediately tells you how many PN have been found in the particular galaxy to date The name is manageable! Can be easily cross referenced to accurate positions which may be updated as astrometry improves but the ID will remain the same Extra-galactic PN workshop Garching May 2004 12

Proposed Nomenclature n n n PN-NGC 7793 -1, PN-NGC 7793 -2 or PN-IC 5175 -32 etc And that’s it! The key `PN’ prefix can be used to search entire CDS databases and will naturally pick up all Galactic and external PN If the PN is just a candidate (rather than confirmed) we could adopt PNC-M 31 -1024 for example Once confirmed the final number would be updated in the PN-M 31 -### list The PNC prefix would create a separate list and confirmed objects would be deleted from this list…is this workable? Extra-galactic PN workshop Garching May 2004 13

What about intragalactic or intercluster PN? ? n n n More problematic Not associated necessarily with a given Galaxy or even cluster Perhaps here we use a: – PNIC-HHMMSSs+/-DDMMSS designation – Or PNX-HHMMSSs+/-DDMMSS n n n Co-ordinate here is more useful as object not easily associated with a specific Galaxy or cluster Surely we can drop the J for J 2000 Also one MIGHT suppose that the specified coordinate precision will be sufficient for such isolated PN…at least for the foreseeable future Extra-galactic PN workshop Garching May 2004 14

Shall we take a vote? n n n Any other suggestions from the floor? It would be good to take a firm recommendation back with me to the CDS that we are all happy with This can then be implemented and, ideally, adhered to even if we also keep our own pet designations for our own discoveries After all any SIMBAD query for a Galactic PN can turn up a plethora of individual indentifiers for the same PN! Does anyone care? – surely any global system that works is a bonus in un-complicating our lives! Extra-galactic PN workshop Garching May 2004 15