T0: UCDs for "em" & "spect"

[Miguel Cerviño]

Hi again :)


>> ... for clarity purpose and hogenity
>> the UDCs I would suggest the following changues:
>>
>> em.IR.K -->  em.IR.2-3um
>> em.IR.H -->  em.IR1500-2000nm
>> em.IR.J -->  em.IR1000-1500nm
>>
....

> may be we should go this way, because the names of those bands can be
> misleading.
> In the case of x- and gamma-rays though there is no confusion, so I  
> would
> keep the existing names...
>

Uhmm, for X-ray and gamma-rays I was asking X-ray and gamma-ray  
people....
I know that UCDs are not for humans, but asking about what  soft and  
hard X-rays mean,
the answer is highly dependent on the asked astronomer. Usually they  
talk  only about
soft and hard. "medium-Xrays" is not understood. In fact, most people  
I asked consider
hard X-ray as aprox 4-10 keV band (from maximmun energy from ROSAT/ 
EINSTEIN to max energy by CHANDRA/ASCA/XMM)..... I do not know, but I  
think that
keep em.X-ray.soft medium and hard is misunderstanding for X-ray  
people. Another example,
ROSAT has a "hardness" ratio that is 0.2 keV-1.5keV (soft) vs. 1-4kev  
(hard) (I do not remember exactly the
energies, sorry) where "soft" and "hard" refers to the detectors in  
ROSAT (but they are used in thsi way in the articles)....

In gamma ray, the situation is similar. You can take a look the  
INTEGRAL instruments, or CGRO ones.
The problem is that each energy range use techniques completely  
different (due to the physics of the process) and em.gamma.hard is to  
wide! It includes from only space instruments to only ground based  
instruments (using the atmosphere as detector). In fact some gamma- 
ray people make distinction between gamma-ray VeryHigh gamma-rays and  
Ultra-High gamma rays as clearly different parts of the
electromagnetic spectrum.... (I was also thinking about INTEGRAL  
where a more defined bands
would be and asset).


>> Finally, I think that the inclusion of em.line would be useful, but
>> only for a very sort list of lines so ... I would agree with
>> Hydrogen lines, but I do think that em.line.OIII should be
>> depreciated (there is several OIII lines!, and if OIII is here, by
>> not, O I, or H+K Ca II etc...? so I propose depreciate  
>> em.line.OIII ...
>>
> the reason for the inclusion of the OIII line is that the doublet  
> 4959+5007
> is one of the strongest lines in emission-line objects (second only to
> Halpha in most cases). There are surveys in Halpha/beta and in  
> OIII, not in
> OI.

ok :)

About other issues. I also agree with include arith and stat in  
"math". I also suggest

        math.stat.moment

that means the order moment of the statistical distribution, i.e.  
mean is 1,
variance is 2, skewness 3, and kurtosis 4....), so allows to include  
more statistical information
(e.j. there is some published data in skewness distributions of  
globular cluster, also are useful
for some synthesis models)


In the case of:


>
>> spect    I worry about spect - this is a kind of data.
>>          If spect, why not image? I predict a few years from now
>>          we will have to change spec and instr.image to  
>> data.spect, data.image, etc.
>>
>
> I agree that data.image and data.spec is a much better model, at  
> least for observations.  After all, what UCD
> often does is to provide generalized "keywords" a la FITS.
>
> On the other hand, the VO theory people might complain that their  
> "images" and "spectra" are not really "data".
>
> Sounds like a problem which has to be put off until later.


Form a theoretical point of view (mine) theory results can be  
considered as "data", produced by a computer
instead a telescope but.... (any case the results of theory will be  
also under a tag <TABLEDATA> isn't  it?
(it is my very particular opinion). (any case there is also a S UCD  
called "meta.modelled"


Finally, about the "line" atom used in "spect"... Uhmm, I do not know  
if there is a more usefull atom. I mean, some lick indices, as  
example, are obtained from "bands" and no lines.... there is no  
problem is it is explicti in the definition that it would refers not  
only to lines but also to bands...

In the same way, I think that

spect.line.intensity  ---> spect.line; phot.fluxDens

Atoms like: profile. width, eqwidth sound ok, but  
spect.line.asymmetry is not included in spect.line.profile?
also for spect.line.broad? (this last I am not sure)


Nice weekend

     Miguel