Date: Wed, 20 May 1998 17:18:59 -0700 (PDT) To: 2mass Subject: IPAC 2MASS WG Mtg #153 Minutes Cc: chas, stiening, bgreen X-Status: Content-Length: 4490 Status: RO IPAC 2MASS Working Group Meeting #153 Minutes 5/19/98 Attendees: T. Chester, R. Cutri, S. van Dyk, D. Engler, T. Evans, J. Fowler, L. Fullmer, D. Kirkpatrick, G. Kopan, J. Mazzarella, H. McCallon, B. Nelson, B. Wheaton, S. Wheelock, J. White AGENDA 1.) Galaxy Orientation 2.) Quality Assessment Calibration 3.) K Magnitude Anomaly 4.) Short-Form Data Access DISCUSSION 1.) Galaxy Orientation T. Chester reported that the preferential orientation of galaxies reported in last week's minutes has been traced to the PSF behavior, as expected. Variations in the PSF derived on a scan-by-scan basis from flattened frames (as opposed to the PSF models used by PROPHOT, which are derived over many more scans and modeled as functions of the seeing) show a convincing correlation with the galaxy preferred-orientation effect. Details of the analysis may be viewed on the web at the URL addresses: http://spider.ipac.caltech.edu/staff/tchester/2mass/analysis /galaxies/rtb/entire_rtb.html http://spider.ipac.caltech.edu/staff/tchester/2mass/analysis /galaxies/rtb/ellipticity.html What corrective action to take, if any, remains undecided. It was pointed out that offline analysis should be done without any presumption that new pipeline software would be the result, although that possibility should not be ruled out. Among the suggestions were (a.) smoothing of galaxy images with a circularizing kernel; (b.) deconvolution (or other method of removal) of the elliptical PSFs, possibly with post-processing smoothing; (c.) simply reporting caveats derived from the observed PSFs on a scan-by-scan basis. Investigation will continue. T. Chester reported that a by-product of this study was the observation of the fact that the scatter in the PSF shape parameter increases considerably when a sub-optimal dither pattern in the frame-to-frame offsets is in effect. The deterioration is bad enough to call into question whether the data taken early in the survey before the best dither pattern was achieved should even be considered for use in the data products. What effect the bad dithering should have on the quality score is still under discussion. 2.) Quality Assessment Calibration D. Kirkpatrick and R. Cutri reported that although progress has been continuing in calibrating the quality assessment parameters, new issues have arisen, and the schedule for finishing this activity reported in last week's minutes has turned out to be optimistic. Some disagreement exists about the extent to which the quality scoring should be automated. A telecon with UMASS is scheduled for tomorrow (Wednesday, May 20). As stated previously, the goal is to calibrate quality on a nightly and scan-by-scan basis, and to be able to update the tile data base to make optimum use of rescanning opportunities. The scoring takes the form of multiplying a base value of 10 by the product of about half a dozen factors normalized to the range from zero to one. These factors include photometricity, seeing variations, and background levels, among other things; factors for extended source quality are needed. It was suggested that bad dithering should be represented by setting the base value to 5. 3.) K Magnitude Anomaly S. Wheelock reported that an anomaly involving K photometry has been found. In five well studied nights, two contained cal scans in which the following strange behavior was observed: in three-band sources with none of the usual problem diagnostics turned on, the K magnitude on one of the six overlapping scans was about two magnitudes fainter than on the other five scans. This happened to four sources in the two nights that showed this anomaly. It has not been seen in J or H. Any ideas on what might be causing this are solicited, and B. Wheaton, S. Wheelock, and R. Cutri will continue to investigate it. 4.) Short-Form Data Access R. Cutri requested T. Chester and T. Jarrett to develop a short-form representation of the extended-source data record. This is needed to go along with the point-source short-form record. One immediate need for these data formats is for use when the data base is locked because a loading operation is underway. Roc also requested J. Mazzarella to arrange for an automatic (or at least convenient) switchover to the short-form data products for people attempting to access the data base when it is unavailable.