Proposed Nomenclature for Extragalactic Planetary Nebulae

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Proposed Nomenclature for Extragalactic Planetary
Nebulae

• Q.Parker A.Acker
• CDS/ULP/Macquarie/AAO

Hopefully the most boring talk during the
workshop!
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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

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Everything is in place at CDS

• A comprehensive web site already exists to assist
  the process.

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The registration form is available on-line..
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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

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How you officially enter a new nomenclature
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So what do we want to use?This is a good forum
in which to decide

• Lets 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

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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.

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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

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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

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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

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Proposed Nomenclature

• PN-NGC7793-1, PN-NGC7793-2 or PN-IC5175-32 etc
• And thats 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
  listis this workable?

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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 PNat least for the foreseeable future

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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!