Date: Wed, 29 Jul 1998 12:00:16 -0700 (PDT)
To: 2mass
Subject: IPAC 2MASS WG Mtg #158 Minutes
Cc: chas, stiening, bgreen
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           IPAC 2MASS Working Group Meeting #158 Minutes
                             7/28/98

Attendees: R. Cutri, S. Van Dyk, L. Fullmer, R. Beck, B. Nelson, D. Engler, 
           S. Wheelock, R. Hurt, T. Jarrett, J. Fowler, J. White, J. Gizis

          
AGENDA

1.) R. Hurt joins 2MASS
2.) New news, old news
3.) 2MAPPS 2.1 redux
4.) 2MASS closes in on the Galactic Center
5.) 2MASS at IAU Symposium 190
6.) New red QSOs and L-dwarf objects
7.) The N-th coming of Gizis


DISCUSSION


1.) R. Hurt joins 2MASS

     R. Hurt has officially joined the 2MASS team.  His duties will include QA
and continuing to adapt M. Brundage's software for the 2MASS QA website.

2.) New news, old news

     The northern facility is now in summer shutdown, due to the monsoonal 
weather in southern Arizona.  R. Beck will be processing northern OPS data for
1998 on elvis, to take advantage of this lull in the action and catch up.  
R. Steining will go to CTIO to replace the southern electronics.  The new
electronics will be swapped in for the old, and test data will be taken.  After
data acquisition, the old electronics will be swapped back in.  These data will
be processed and analyzed at IPAC.  Some changes are anticipated, e.g., in the
southern darks, as a result.  The stripe artifact may improve with the new
electronics.  The stripe artifact is an electronic echo resulting from a bright
star on an image, with lots of counts over a small area of the array.  This 
artifact also occurs for the northern data.  The stripe artifact flag is now 
functional in MAPCOR.  (J. Fowler wittily remarked that this should really be 
known as the "stars&stripes" flag.)
  
     R. Cutri emphasized that he will need bodies and eyes on these test
data.

     R. Cutri thought that the Science Team meeting had been quite successful.
Congrats all around to all IPAC 2MASSers, especially those working on the
pipeline.  He felt that presentations made by individuals were quite good, and
that excellence and accomplishment had been demonstrated at the meeting.   
However, a concern still exists for the scan overlap bias and other problems.
He would like to be able to throw the switch soon on the southern pipeline.

3.) 2MAPPS 2.1 redux

     R. Cutri discussed the various bugs that still exist in 2MAPPS 2.1,  
includingthe position bias between scan overlaps, on which H. McCallon 
reported (see WG Mtg #156 Minutes).  The problem has likely been fixed, with
H. McCallon (not present) to confirm this.  L. Fullmer will check on this.  
Another problem is the southern PSF.  W. Wheaton produced a model average PSF 
and variance map.  From chi^2 analysis, it is clear that the variance is being 
underestimated.  The chi^2 distribution and dispersion in the photometry is 
unacceptably large and divergent.  Employing a single PSF and variance map seems
to work better.  This remains an outstanding problem.

     S. Wheelock was uncertain whether the 980403s RTB night had been 
calibrated.  S. Wheelock and L. Fullmer will use T. Evans' procedure to extract
MAPCOR lookup table information from the latest run using the new southern
PSFs.

     R. Cutri discussed at length the photometric scan-to-scan bias, which is
as much as 4 to 6 percent.  Is this a flatfield residual?  The answer is, most
likely, "no".  Thanks to G. Kopan, in part, it appears that it is due to the PSF
being variable, both spatially and temporally.  (This cause of the problem was
smoked out by comparing the aperture and profile photometry.)  This effect is
intolerable in the south, where it can reach up to 9 percent, and thus does not
meet Level 1 requirements.  The problem is probably particularly bad for the
south, due to the good seeing there.  R. Cutri is seeking a solution to this
problem.  S. Van Dyk remarked about the variable PSF switch that exists in 
DAOPHOT.  Clearly, this is not a possible solution.  A lot of analysis is 
necessary to find an intelligent final solution.

     R. Cutri wants to either take the time now to make the proper correction, 
or start processing, develop the correction, and apply it retroactively to data
already processed.

     R. Cutri encouraged one and all to look at the most recently-processed RTB
nights as soon as possible.

4.) 2MASS closes in on the Galactic Center

     The nights 980702s and 980705s are currently processing on rex.  These
nights contain scans of the Galactic Center.  These scans should serve as an
excellent test of how good is the sky background estimator, versus far less
dense regions of the sky.  From the scans of Baade's Window (on 980319s) we
already know that 3 to 5 percent of the stars returned magnitudes 99.999, 
especially in H.  Source extraction records are already being shattered for
the scans that have been processed so far.  These scans should certainly make 
one heckuva nice gallery image mosaic.

5.) 2MASS at IAU Symposium 190

     S. Van Dyk reported on his participation at IAU Symposium 190, "New Views
of the Magellanic Clouds," held at the University of Victoria, BC, Canada,
July 13-17.  2MASS had a poster paper on observations of the Large Magellanic
Cloud (LMC).  A bit shy of a 1 million sources have been extracted from those
observations.  The poster presented the color-color and color-magnitude diagrams
derived from the extractions, showing many K and M giants, red and blue
supergiants, AGB stars, carbon stars, and dust-enshrouded AGB stars, as well as
foreground contamination.  The ages of the giants are consistent with the 
current age estimates of the intermediate-age population in the LMC, about 2 to
5 Gyr.  Many likely new carbon stars have been discovered throughout the LMC 
observed so far.

     These results are consistent with what the DENIS team is finding, which
is quite satisfying, given the complementary nature of the bandpasses used for
each survey.  Both surveys have their strengths and weaknesses in identifying
the red populations in the LMC.  (This agreement is not trivial; S. Van Dyk, for
instance, has been part of two VLBI collaborations which are observing the same
object with the same telescopes, same bandpasses, and getting different results;
here, two surveys are using different telescopes, different bandpasses, to 
observe the same object, and are getting very similar results.)

     The poster also put emphasis on the 2MASS Sampler this fall.  S. Van Dyk
made a large stack of 2MASS publicity fliers available to other participants
at the poster.  He was selected by the SOC to give a two-minute oral summary
of the poster, where he made mention of the public nature of the data, the
various 2MASS websites, and future data releases.
     
6.) New red QSOs and L-dwarf objects

     B. Nelson and D. Kirkpatrick, on a recent Palomar 5-m run, have found,
from their color-selected (J-K > 2) sample of 35 candidate objects derived from
2MASS source extractions, 12 new AGNs and 1 possible L-dwarf.  Visual inspection
of raw spectra shows a mixture of other M and L dwarfs; 2 possible dwarfs could
not be detected, and are presumably being observed at Keck.

     B. Nelson reports that about 60 percent of his candidate objects turn out
to be QSOs or AGNs.  The other 40 percent are double stars, M dwarfs, red 
galaxies with featureless spectra, the occasional carbon star, or, in fact, 
L-dwarf objects.

7.) The N-th coming of Gizis

     J. Gizis is again visiting IPAC and filling in for D. Kirkpatrick on QA.
His only remark is that the QA webpage needs improvement.  He has found what
can be called the "K donut," on two different nights, 970724n and 970731n.  A
ring-like feature sporadically appears on K images only, and must be something
that is out-of-focus in the K channel.  It is about 20 to 30 coadded pixels in
size.  It may affect the K photometry.  This artifact, of course, affects the 
quality of those nights.

     One last note made by R. Cutri and J. Fowler is that a lot more asteroids
are coming through production lately, as these nights must be sampling more of
the ecliptic.  Soon, statistically significant color, brightness, and number 
distributions should be obtainable for these objects.

------------------

     IPAC 2MASS Working Group Meeting #158 Minutes ERRATUM

Note:  the report from J. Gizis (Agenda Item 7) about the nature and
quality of the QA webpage is inaccurate.

Gizis' comment was regarding the 'SCAN' QA page, which needs improvement.

The 'NIGHT'ly QA page, written by L. Fullmer, is working fine and is being
improved and revised as recommendations arise.