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Next: Sample Selection and

Comparison of GALWORKS and IRAF's STSDAS Photometry in a Polar Field

Jessica Rosenberg
UMASS

Tom Jarrett
IPAC

We have analyzed the photometry of 4 galaxies observed with the 2MASS prototype camera and processed by the 3-channel GALWORKS (hereafter referred to simply as GALWORKS) using the STSDAS package in IRAF. Although it is not a statistically illuminating sample, it is an interesting comparison with the 2MASS photometry and gives us a first guess as to what we can hope for from the 3-channel data. The photometry itself has been broken up into three parts. The first part is the examination of fixed radius circular and elliptical photometry where all of the parameters for the IRAF photometric determinations are set to match those from GALWORKS (the individual J, H, and K scans were merged to form a "3-channel" data set; see Appendix D for details). This first part is a sanity check since the answers from GALWORKS and IRAF should be identical or nearly so. The second part of the analysis consists of examining the petrosian and isophotal radii and magnitudes for circular and fixed elliptical apertures. The parameters of the apertures are again set to match the GALWORKS parameters, but the petrosian and isophotal radii (and hence magnitudes) are selected independantly. In the final part of the analysis we allow IRAF to determine the parameters for the galaxies independant of the GALWORKS values and compare the ellipticities and position angles determined in this manner as well as the petrosian and isophotal photometry to the pipline results.





Tom Jarrett
Thu Feb 6 16:44:06 PST 1997