Catalogue Availability

[jg <jg@jgws.freeisp.co.uk>]

Someone asked a while ago re thoughts on catalogues for CD inclusion.

It's a bit late now, but I've some thoughts for future reference.

It seems some catalogues I've got aren't automatically on the Guide CD
or such as I thought, and I must have sourced them elsewhere, either
through NASA ADC CDs or just plain downloading.

These catalogues would be best placed unzipped on a CD so people could
use them directly from there without wasting hard disk space, should
such a CD ever appear.

They are fairly big and even gzipped may be several megs to more and
this may put folk off downloading them.

Meanwhile, if is not really feasible to drop even the ~ 35,000 objects
on TASS CD 23 with 30+ pairs of observations through the catalogues via
the ViZieR service, let alone the full 94,500, and this alone is
probably why some comparisons have not been made.  Granted subsets of
the reddest or bluest objects can be found, or other subsets, but these
may still add up to a 1,000 or so objects unless one is being really
restrictive.  A list of objects bluer than V-Ic 0.1 adds up to 319 _even
if_ all the ones with less than 3 observations and/or negative
Welch-Stetson index are ditched, well over a 1,000 if not.

This is probably why some catalogue tests have not been done.

The following catalogues are a few suggestions based on suggested
catalogue tests from earlier posts.  I might have missed a thought on a
coupla catalogues.  These are easy for _me_ to mention, but obviously
someone with bandwidth, CD burner and a bit of data manipulation skill
is the one who is going to get stuck doing it, if it is done at all ;)


Catalogues:

ROSAT xray catalogues.

The ROSAT All Sky Survey has several catalogues of varying kinds, and
sometimes from different reductions via two different groups.

The appropriate three to use, I think, are the RASS Bright Source, the
RASS Faint Source and the RASS Second Pointed Source catalogues.

The latter contains a flag denoting when xray variability was possible. 
As well as this flag being null when it is not, there is also a flag
denoting when there was not enough data to say either way, which is
always useful.

That's 3 + 22 + 36 = 61 Mb


IRAS

Both the Point Source and the Faint Source Catalogues.

I've on occasion noted suspected variables in the faint source catalogue
that aren't in the PSC.

That's 40 + 38 = 78 Mb


MSX_5C

Although primarily Galactic plane this infrared catalogue also contains
a small subset of data specially taken to cover a region missed by IRAS.

Again catalogue data contains flags for suggestion of variability in the
(designer) IR passbands used.

This catalogue comes in a strange bunch of zonal files that need
unpacking, merging and then for many purporses re-sorting on RA.

When I did this the eventual file added up to 112 Mb


2MASS 2nd Incremental Catalogue.

Though not currently applicable as the region around +7 degrees
declination does not as yet appear to have been released by the 2MASS
people, at least not for most of the RA range on CD 23, this is an
interesting photometric reference with positions mostly good to an
arcsec by all accounts.  Brian Skiff has had interesting thoughts on use
of the three colour photometry for little diagnostic things, if I can
remember where they were said, probably vsnet ;)

Anyway, when it first came out I used the GATOR interface to select a
subset of objects that were all brighter than J = 10 and had values for
all of the J, H and Ks bandpasses.  Some things are just so bright in
the far red to near infrared that they are often overexposed in Ks and
no sensible magnitude can be gained.

Fortunately GATOR did (it's changed a bit and I haven't used it in a
long time) all the processing at their end on their database package and
I merely had to wait for an email to notify me of a temporary ftp file
when it was finally done.  Fortunately resume was supported else I'd
have been stuffed.

Anyway, the resultant datafile was 76 Mb big.  A similar dataset down to
a more useful cut off of say J = 12 may be twice as big if not bigger,
so lets guesstimate 180 Mb kind of arbitrarily.

Someone with readily available company or edu type bandwidth would be
needed to obtain such a subset.

There's ostensibly a DVD available for scientific use on request, but I
don't know how many people bother with a DVD player in their 'puter
(I've no need of one), or how readily available the DVD is in actuality.

(Of course maybe only data for say 0 to 10 degrees declination will be
needed which would seriously reduce the size of the file).


So that's about 430 Mb of data.  Much of a CD.  Fillers could be the
latest GCVS, NSV, NSV supplement and newvar.cat at the time, currently
about another 30 Mb altogether.

Many other catalogues could be added but most are pretty small,
especially when zipped, and fairly easily obtained from CDS or ADC.  I
may have missed an obvious one (I've deliberately excluded mention USNO
A or B or UCACs or GSC1 or GSC2 cos they are quite something else).

Simply these massive catalogues are difficult to match large numbers of
objects against.  There are online interactive routes, some like 2MASS
will even accept large batch lists, but the results still have to be
downloaded afterwards, and could be quite big.  I think some people
would rather test any and all future TASS data against such catalogues
directly with their own perl or whatever scripts.

If this becomes of interest at some point I can provide the ftp urls and
interface details for the above data.

Cheers

John

John Greaves
UK