[Fwd: Re: Quasar classification (in Re: WD-Ontology)]

[Ed Shaya]

Kjetil

This is not quite so black and white here.  There may have been the
intention on someone's part to ensure that something is classified as a
QSO or an AGN but not both.  It is customary, to call it a QSO when
there is no observed sign of an underlying galaxy and then to change its
classification when (and if) deeper imaging reveals a galaxy there.
Some QSOs have defied extremely deep and intensive searches for an
underlying galaxy.  This type of problem needs some more examination.
Another related problem comes with Seyfert I and Seyfert II which are
now thought to be the same class but observed from a different viewing
angle.

Ed


Kjetil Kjernsmo wrote:
> On Wednesday 21 February 2007 16:22, Andrea Preite Martinez wrote:
>> QuasiStellarObject
> 
> Sorry to be bursting in from the sideline here. :-) I have not worked in 
> astrophysics for a few years (rather worked with the Semantic Web), but 
> I was confused about both the chosen name and the RDF that follows it. 
> I don't know if it is appropriate to address my concerns in this forum, 
> or if it has been decided elsewhere, but here goes:
> 
> I have been of the impression, especially from Julian H. Krolik's 
> excellent text book on Active Galactic Nuclei, that the AGN community 
> now prefers to "forget" that there ever was anything "stellar" in 
> quasars. Allthough it has great historical significance, it now only 
> serves to confuse people. I think that the community generally 
> recommends that "quasar" is adopted as a new word, and that if one 
> wants to distinguish different kinds of quasars by their radio 
> properties, they should be called "radio-quiet" and "radio-loud". 
> 
> Quasars are clearly Active Galactic Nuclei, however, and so the RDF/XML 
> OWL fragment confused me even more: 
>   <owl:Class rdf:ID="QuasiStellarObject">
>     <owl:disjointWith>
>       <owl:Class rdf:about="#ActiveGalaxyNucleus"/>
>     </owl:disjointWith>
>   <owl:Class>
> 
> I'd rather say that:
>   <owl:Class rdf:ID="QuasiStellarObject">
>     <rdfs:subClassOf>
>       <owl:Class rdf:about="#ActiveGalaxyNucleus"/>
>     </rdfs:subClassOf>
>   <owl:Class>
> 
> and if using the terms I think the AGN community would prefer, 
>   <owl:Class rdf:ID="Quasar">
>     <rdfs:subClassOf>
>       <owl:Class rdf:about="#ActiveGalaxyNucleus"/>
>     </rdfs:subClassOf>
>   <owl:Class>
> 
> I hope that this input is useful and that mine or other's confusion can 
> be cleared up.
> 
> Best,
> 
> Kjetil

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