T. Jarrett, IPAC
(970714)
Three 1-degree scans were acquired for fields under consideration as standard (calibration) fields. The fields are centered on two faint galaxy clusters, one x-ray selected and the other an Abell cluster. This memo describes the performance of GALWORKS on these fields, with the ultimate goal to choose the best field for standard/calibration observations during the 2MASS survey.
Bottom Line: We recommend the area comprised by Scan 106 for use as a calibration/standard field.
Scan 105, Night of 970602
This scan is centered upon an x-ray cluster, galactic coords: glong = 73 , glat = -19. Several galaxies were detected (see below), albeit they are somewhat faint, most have K > 13.0. Two galaxies are bright, but also have stellar contamination.
In addition to the galaxies, a few false detections were made with GALWORKS. The false sources consist of pieces of bright stars (see below) and double stars.
Most of these objects can be cleaned from the extended source catalog by carefully tuning the scoring parameter thresholds. More discussion on this matter will be given at the end of this memo.
Scan 106, Night of 970602
This scan is centered near an Abell cluster, galactic coords: glong = 78 , glat = -27. Several galaxies were detected, of which the brightest ones are free of stellar contamination.
And a few false sources, again mostly due to bright star contamination:
Scan 107, Night of 970602
This scan is located next to scan 106, centered on an Abell cluster, galactic coords: glong = 78.5 , glat = -27. A few more galaxies were detected in this scan compared to its neighbor, scan 106, although dominated by faint little galaxies.
And a few false sources, again mostly due to bright star contamination:
Recommendation:
Scan 105 has the highest density of galaxies, compared to scans 106 and 107, but the stellar density is also much higher; consequently, the brightest galaxies in scan 105 are contaminated by starlight.
Scans 106 and 107 have about the same density of galaxies, but a couple of the brighter galaxies in scan 107 are close to stars and may be contamined. The edge seems to be with scan 106. The area comprised by Scan 106 is therefore the recommended area for use as a calibration/standard field.
