Comparing the 2MASS Measurements of Axis Ratio to the Optical

After the testing of GALWORKS on the simulation galaxies was complete, we then proceeded to real data. The SA57 polar field was used (see document GALWORKS Results for Four Scans in SA57: Algorithm 1 for further information on the SA 57 field) and the resulting values for the J, H, K, and the super-coadd axis ratios were determined. Optical axis ratios were determined for comparison from the digitized sky survey (DSS) images. The DSS images were processed using the STSDAS isophote fitting package in IRAF.

The results of the axis ratio comparison are shown in Figure 7 The main thing to note is that there are no systematic differences between the 2MASS and DSS determinations of axis ratio, although there is a fair amount of scatter. One should note that the 2 points for which the 2MASS fits are worst (2MASS measures b/a to be 1.0 while the DSS value is about 0.55) are very faint galaxies. Although there is a lot of scatter in the 2MASS to DSS plots, there is relatively little scatter in the J versus K or the J versus H plots which seems to indicate that we are doing well internally. The scatter in the 2MASS versus DSS plots may be caused by differences in the galaxies between the optical and the infrared.