i. 2MASS XSC vs. VLA FIRST Astrometry
We compare the equatorial coordinate positions of the 2MASS XSC standard positions (based on J-band peak) and the VLA FIRST radio sources. Since both surveys should have excellent astrometry, we restrict the comparison to those sources within a 5´´ search radius (which also minimizes the astrophysical differences between radio and near-infrared intensity peaks). Note that the FIRST survey is restricted to declinations between -10° and +60°.
About 23,000 matches between 2MASS and FIRST, found using a search radius of 5´´, result in the following statistics:
In Figure 1 we show the 2MASS/ FIRST positional comparison as a function of declination. In Figure 2 we show the global comparison in both right ascension and declination. In Figure 3 we show a histogram of the 2MASS vs. FIRST positional comparison.
|Figure 1||Figure 2||Figure 3|
[Last Updated: 2002 Aug 4; by T. Jarrett]