[vsnet-survey 42] 2MASS 2nd incremental catalogue...

[no name <crawl@zoom.co.uk>]

The 2MASS 2nd Incremental Catalogue has been released for a little while
now.

It can be searched via the two frame interactive server at:

http://irsa.ipac.caltech.edu/applications/CatScan/

where further links re usage, documentation etc can be found.  The home
page is 
http://irsa.ipac.caltech.edu/

which also includes information on several NASA supported IR surveys [eg
IRAS, MSX], but contains the main, and other, 2MASS links [including
quite a nice gallery].

Near-IR photometry and astrometry are given for a large number of stars
for an increasingly large area of sky.

The photometry is in passbands equivalent to J, H and K, but I do not
think they are strictly Johnson-Cousins passbands, and may be slightly
different.  2MASS J magnitudes and DENIS J magnitudes do not appear to
be the same, with a  slight offset, based on a cursory inspection of a
handful of common objects.

The astrometry appears to be good to about an arcsecond, or better.

The probably most interesting aspect is that objects that can be found
on digitised visual survey plates but are _not_ in USNO A2.0, can appear
in 2MASS if in a part of the sky for which data has been released.

An example is Nova LMC 2000, where two nearish plate limit stars
adjacent to the Nova's position are on the survey plates, not in USNO
A2.0 [or the DCMC = DENIS Catalogue of Magellanic Clouds for that
matter], yet are in 2MASS, thus giving positions and some photometry
[albeit IR!].

Another example is the existance of MISAO variable candidate[s] with no
known counterpart in either USNO Ax or IRAS catalogues [or other cats],
but with a 2MASS counterpart.

Although only postage stamp size fields of maximum 1 degrees can be
downloaded, there is a facility to send in a batch list request that
will be filled by email later if several positions are of interest. 
Check coverage first.  In any event, the sheer number of 2MASS objects
makes the handling of data for sizeable fields difficult, and the time
needed by the server's search engine long, so the small size of data is
ironically a bonus!

If the above URL is used to download data from the IRSA 2MASS 2nd
Incremental Catalogue server, with the SHORT default catalogue output
format selected [plus 3 additional fields hand selected for J-H, H-K and
J-K, making 26 fields in all] the following TDF can be used to plot the
positions in Guide 7 as small red triangles _centred_ on the 2MASS
positions.  HELP and MORE info give astrometry & photometry information,
USNO A red & blue mags where applicable, and the arcsec offset and PA to
nearest USNO A counterpart when one exists.

The ascii data downloaded from IRSA must be appended/cut&paste to a
master file called 2MASS.dat which will live in the Guide home
directory.  Non-data lines should be deleted. [ie it is possible to use
2MASS data, but not necessarily straightforward].

Lines are demarked with ! : any not so demarked have folded on email
transmittal, and should be fixed in an editor.  The TDF should be cut
and paste as a file, with the superfluous ! symbols removed, in the
Guide 7 home directory.  Fields will need to be less than a degree for
it to be manageable, and import of DSS images and/or USNO A2.0 data may
be helpful for field recognition.  2MASS is not part of CDS Aladin yet,
and this may be the only way to handle this data at present, short of
writing a dedicated plotting program.

[NB currently the DENIS server and I are not getting along very well,
especially in respect of TDF utilisation.  This is a shame, as the DENIS
data includes I band photometry, albeit modified gunn i, though this may
soon be the norm (eg SDSS, FAME, etc).  It is also restricted to the
Southern Hemisphere].


John

=============================================TDF snip
!file 2mass.dat!
!title 2MASS!
!RA H   2   8!
!units0 -2!
!de d  14   8!
!~b 50  14 2MASS J%s\n\n!
!~r  2   8 RA2000    %R!
!~r 28   4  error  %s"\n!
!~r 14   8 DEC2000 %D!
!~r 36   4   error  %s"\n!
!~b 66   6 \nJmag   %s!
!~r 74   5   error  %s!
!~b 81   6 \nHmag  %s!
!~r 89   6   error  %s!
!~b 96   6 \nKmag  %s!
!~r104   6   error  %s!
!~b199   6 \n\nJ-H   %s\n!
!~b208   6 H-K   %s\n!
!~b217   6 J-K   %s\n!
!~b156   5 \nblue mag  %s\n!
!~b164   5 red   mag  %s\n!
!~r173   5 \nDist. Opt : %s\n!
!~r182   4 Angle Opt : %s\n!
!!
!epoch 2000!
!type sc5;m10,10;l-10,10;l0,-12;l10,10;!
!goto spaces!
!goto case!
!label spaces!
!field 0 10!
!mag lim 0!
!shown 1!
!end!
===================================================end-snip

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