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

2. 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. 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. 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 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

3. Extra-galactic PN workshop - Garching May 2004 3

4. 4 Everything is in place at CDS A comprehensive web site already exists to assist the process…. A comprehensive web site already exists to assist the process….

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

6. Extra-galactic PN workshop - Garching May 2004 6 Galactic PN They use PN Glll,l+/-bb.b They use PN Glll,l+/-bb.b This is actually not sufficient even to discriminate amongst all the known galactic PN 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 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…. 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 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

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

8. 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 Let’s look at the initial proposal applied to a galaxy in NGC7793 for example PNGNGC7793J2357499-323520! PNGNGC7793J2357499-323520! This is quite a mouthful even if we replace NGC with N! 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….. 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 We may need PNGNGC7793J23574998-3235206 if we are to use this system effectively

9. Extra-galactic PN workshop - Garching May 2004 9 What is in a name? Are there any tractable alternatives? Are there any tractable alternatives? Clearly the host galaxy is a key parameter immediately placing the PNe in context 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 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.. 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…. Perhaps an RA/DEC concatenation is not the best way forward….

10. Extra-galactic PN workshop - Garching May 2004 10 So what can we do? For extragalactic PN all the objects occur within quite a small region – a few tens of arcminutes for most 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 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… 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…

11. 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 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 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 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… i.e.when we can find PNe within a hundredth of an arcsecond from another in a distant galaxy…

12. 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 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.. 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 Also the largest number immediately tells you how many PN have been found in the particular galaxy to date The name is manageable! 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 Can be easily cross referenced to accurate positions which may be updated as astrometry improves but the ID will remain the same

13. Extra-galactic PN workshop - Garching May 2004 13 Proposed Nomenclature PN-NGC7793-1, PN-NGC7793-2 or PN-IC5175-32 etc PN-NGC7793-1, PN-NGC7793-2 or PN-IC5175-32 etc And that’s it! 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 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 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 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? The PNC prefix would create a separate list and confirmed objects would be deleted from this list…is this workable?

14. Extra-galactic PN workshop - Garching May 2004 14 What about intragalactic or intercluster PN?? More problematic More problematic Not associated necessarily with a given Galaxy or even cluster Not associated necessarily with a given Galaxy or even cluster Perhaps here we use a: 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 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 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 Also one MIGHT suppose that the specified co- ordinate precision will be sufficient for such isolated PN…at least for the foreseeable future

15. Extra-galactic PN workshop - Garching May 2004 15 Shall we take a vote? Any other suggestions from the floor? 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 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 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! 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! Does anyone care? – surely any global system that works is a bonus in un-complicating our lives!