Dimensionless units

[Igor Chilingarian]

Hello,

On Fri, 18 Feb 2005, Ed Shaya wrote:

>
> I wonder, is a SED only allowed to be spectra?  If I have Fnu/pc (flux
> along a disk) and Fnu/sec (rate of change of the flux), are these
> allowed in a SED?  If so then we will need to rely on UCD or ontology to

This is quite an important point, connected to the propositions I made several
weeks ago. For a moment, there are some allowed "flux" units (in the SED Data
Model v.0.92+) that have nothing to do with spectrophotometry, for example
 "arith.ratio;phot.fluxDens" -> "Flux ratio of two spectra". I proposed in one
of my mails handling continuum-normalized fluxes, that are niether photometric
information.

The question is
Q1: Do we want to handle such kind of "spectra" in the SED DM 1.0?

If the answer is "yes, we do want to handle any information depending on the
spectral coordinate", there is a second question:

Q2: Why don't we want to extend this sample of "something as a function of
lambda"  and to handle, say, extinction laws, or theoretical
synthetic spectra that have units of "W/kg", but not "W/m^3"?

During last AVO demo such synthetic spectra were shown on the same plot with
spectrophotometrical data, and the question about it was raised.
Actually, to compare directly synthetic spectra (for galaxies) with observed
data, one should assume some mass and distance for this "theoretical
object".

With best regards,
						Igor