Milky Way Tomography with the SkyMapper Southern Survery: II: Photmetric Calibrations for the Second Data Release of the SkyMapper Southern Survey
In this paper, we apply the spectroscopy-based stellar color regression (SCR) method proposed by Yuan et al. to perform accurate photometric calibration for the second data release of the SkyMapper Southern Survey (SMSS DR2). By using a total number of over 200,000 dwarf stars with stellar atmospheric parameters taken from the GALAH DR3 and with homogeneous accurate photometry from the Gaia DR2, strong reddening dependent zero-point (ZP) errors are detected in the photometric catalog of SMSS DR2. The ZP errors are nearly zero at nil extinction and then steadily increase with E(B − V ), and can reach as large as 0.24, 0.23, 0.03, 0.02, 0.04, 0.05 mag in uvgriz bands, respectively, at E(B − V ) ∼ 0.5. The errors are largely from the dust term in the transformations used by SMSS DR2 to construct photometric calibrators from the Pan-STARRS1 (PS1) photometry. Our study also reveals small but significant spatial variations of the ZP errors in all six bands. By properly correcting for the reddening and spatial dependent systematics, final ZP accuracies of 6.7, 5.7, 2.1, 2.5, 1.5 and 1.6 mmag at uvgriz bands have been achieved for 50 per cent calibrated fields by our SCR technique.
