2MASS R1 Saturation Source Extraction Analysis
We compared the J, H, Ks magnitudes for the R1 Saturated sources derived from the second OPS test with 2MASS magnitudes estimated using Version 3.0 of the Cohen and Walker Atlas of Calibrated Spectra (CW). The 2MASS magnitudes of the CW stars were determined by integrating the spectra over the 2MASS relative response functions, converting to flux density and magnitude using isophotal bandwidths and zero magnitude fluxes provided by Martin Cohen. Thirty-eight of the 2017 OPS test sources have CW counterparts.
Results
- Most of the R1 magnitudes are within 1 sigma of the CW magnitudes. The error estimates are the root sum square of the OPS error estimates and the integrated CW errors (which are much smaller than the OPS errors).
- The distribution of residuals (2MASS - CW) is tight with a spread of 0.1 magnitudes in Ks and slightly larger in J and H.
- There is a bias between 2MASS and CW of 0.06-0.09 magnitudes with 2MASS fainter than the CW estimates. Independent calibration of CW stars shows that the CW values are too low by 1%. Therefore, the bias is in an opposite sense to the known CW bias.
Mean and Standard Deviation of 2MASS-CW magnitudes
| Band | Mean | S.D. |
|---|---|---|
| J | 0.090 | 0.154 |
| H | 0.089 | 0.124 |
| Ks | 0.064 | 0.106 |
Histograms of Distribution of 2MASS-CW magnitudes
| Band | Raw 2MASS-CW | (2MASS-CW)/1 sigma RSS error |
|---|---|---|
| J |
 |
 |
| H |
 |
 |
| Ks |
 |
 |
Scatterplots of 2MASS and CW magnitudes
| Band | 2MASS vs. CW | (2MASS-CW) vs. 2MASS |
|---|---|---|
| J |
 |
 |
| H |
 |
 |
| Ks |
 |
 |