Version 1.9.9 of UCD definition

[Anita Richards]

At the interoperability workshop following ADASS, there was some mention
of contradictions between the spectral divisions in the UCD2 document and
the groupings in RM v0.82.

There was also debate about whether and where an mm or sub-mm band should
be introduced in RMv0.82.

I think that consistency between UCD2 and the RM (whatever is the stable
outcome for defining the Registry) would be very useful but in fact the
discrepancies are minor.  Personally, I hope that we do not spend much
time discussing the exact divisions as we cannot avoid splitting the
coverage of some present instruments, let alone future ones.  However it
might be sensible to be guided by the current/immediate future major
observatories. Perhaps the responses to the SSA / spectral data model
questionnaire might help.

These are my suggestions:
The boundaries of the spectral UCD2s are consistent with fitting into the
RM categories with minor changes:

Some of the UCD2 frequency ranges at the high freq end of IR have become
transposed (I think - it is indeed hard to think in 3 sets of units!)

I apologise for having created confusion over the new mm band in RMv0.82.
The proposed range of ALMA is 30 - 900 GHz according to the web page.  In
fact, I understand that initially the lower limit is more like 86 GHz.
Therefore I suggest that consistency can be achieved by having instead:
SUBMM  100 micron - 3 mm (100 - 3000 GHz)

The RMv0.82 x-ray regime goes from 0.12 - 120 keV; the UCD2 regime goes
from 0.12 - 12 keV
Accoding to their web pages, CHANDRA covers 0.1 - 10 keV (I have also been
told 0.12 - 12...) and XMM covers 0.15 - 15 keV; ROSAT was within this.
The CRO covered > 30 keV and SWIFT, 15 - 150 keV

Thus, to keep the 'decades', this seems more suitable:
XRAY 0.12 - 12 keV (as per UCD2)
GAMMARAY > 12 keV
but maybe a high energy astronomer can advise....

OVERLAPPING DATA

Suppose that I have a catalogue with data taken around 1 micron.  I hope I
am right in thinking that the Registry entry can contaiin both Optical and
IR as values of the relevant spectral coverage keyword, and this is used
OK in searches etc.

How will the UCDs be used? As I understand it, in order to use Vizier or
the Aladin SED tool to search for e.g. radio observations between 1.3 and
1.7 GHz (radio L-band), the software would look for UCDs
em.radio.750-1500MHz and em.radio.1.5-3GHz.  However there may be
catalogues giving radio observations or flux densities between 1.4 and 1.7
GHz.  This might or might not give the exact observing frequency, but for
many purposes the general flux density or image would be useful.  As I
understand it, this would simply have the UCD em.radio and would not be
found.  This is _not_ a plea to divide the ranges differently, but a
reflection of the fact that we are no longer restricted to observing in
well-defined filters.  Broad-band receivers and optical fibres in the
radio, ALMA, space observatories etc. mean that we observe at all
frequencies seamlessly, and sensitivity to higher redshifts means that
lines no longer fall even in a single regime.

Maybe there is a solution already.  If not, the only satisfactory
things I can see are to do one of the following:
* allow bracketting UCDs e.g. em.radio.0.75-3GHz
* allow two (or more) UCDs to a column, where these are adjacent (up to a
  sensible max)
* not use the fine divisions in UCDs, but treat frequency like position
  and treat every query as a 1D cone search, ie a linear segment search.

cheers
a

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Dr. Anita M. S. Richards, AVO Astronomer
MERLIN/VLBI National Facility, University of Manchester,
Jodrell Bank Observatory, Macclesfield, Cheshire SK11 9DL, U.K.
tel +44 (0)1477 572683 (direct); 571321 (switchboard); 571618 (fax).