IPAC 2MASS Science and Analysis Working Group Meeting #4 Minutes
IPAC 2MASS Science and Analysis Working Group Meeting #4
Attendees: T. Chester, R. Cutri, T. Evans, L. Fullmer, T. Jarrett,
D. Kirkpatrick, B. Light, C. Lonsdale, M. Moshir, S. Terebey
T. Chester and T. Jarrett: have been studying the possibility
of tracking seeing within a scan using a much smaller number of stars
than currently used by G. Kopan for the scan-averaged seeing estimator
pfrac. For stars, the `shape' parameter of GALWORKS tracks seeing well
on a scan-by-scan basis. The sigma on the shape, however, appears to
increase with increasing seeing (contrary to Tom's expectation that it
ought to decrease with increasing seeing) and to also correlate with
the seeing. Some scans were found to have anomalously high sigmas,
indicating a possible problem with very bad seeing blowing up somewhere
throughout the scan. This raised the concern that we would be able to
identify scans with poor seeing but not to track seeing well throughout
Tom then plotted shape within a scan, using a six-star average to
compute this seeing estimate. He found that in the previously
identified anomalous scans there were regions within the scan where
shape and sigma went wild.
Subsequent to the meeting Tom discovered that the anomalous sigmas were
due to contamination of his `star' sample by galaxies, and that with
these galaxies removed the shape parameter appears to track the seeing
quite well. We will therefore investigate using shape, determined
prior to GALWORKS in the pipeline, as a means of inputting to PROPHOT a
monitoring of the seeing, so that PSF can be revised within a scan, as
- D. Kirkpatrick: reported on his search for
astronomically interesting objects in the 92-94 database that he and C.
Beichman have just finished cleaning up (see last week's minutes).
Using the APM database, Davy searched for extremely red objects; those
with R-K>=6. Out of 54 objects meeting this criterion (the search was
restricted to sources having a confirmation in the APM database), 10
are likely to be real. Four are M giants, 3 previously known (and in
SIMBAD), and the fourth so identified from its colors. An additional
4 are probably late-type dwarfs. One is the previously known Pleaides
brown dwarf candidate, and another is T. Chester's double M6 star. Two
are previously unknown. The final two objects are of unknown nature
and are candidates for imaging and spectroscopy; unfortunately neither
are accessible for a few months.
Davy is now turning his attention to objects in the R-K=3-4 range, with
unusually red J-K or H-K color; such objects would be candidate red
QSOs, by analogy to the colors of the PG QSOs.