Proposed Nomenclature for Extragalactic Planetary Nebulae

1. 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

2. You know it makes sense… • 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

3. Extra-galactic PN workshop - Garching May 2004

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

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

6. Galactic PN • 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.bA,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

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

8. So what do we want to use?This is a good forum in which to decide… • Let’s look at the initial proposal applied to a galaxy in NGC7793 for example • PNGNGC7793J2357499-323520! • 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 PNGNGC7793J23574998-3235206 if we are to use this system effectively Extra-galactic PN workshop - Garching May 2004

9. What is in a name? • 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

10. So what can we do? • 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

11. Things to consider • 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

12. Nos suggestion du jour • 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

13. Proposed Nomenclature • PN-NGC7793-1, PN-NGC7793-2 or PN-IC5175-32 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-M31-1024 for example • Once confirmed the final number would be updated in the PN-M31-### 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

14. What about intragalactic or intercluster PN?? • 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 • Co-ordinate here is more useful as object not easily associated with a specific Galaxy or cluster • Surely we can drop the J for J2000 • Also one MIGHT suppose that the specified co-ordinate precision will be sufficient for such isolated PN…at least for the foreseeable future Extra-galactic PN workshop - Garching May 2004

15. Shall we take a vote? • 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