Oral Presentation

A new method for color calibration to a few mmag accuracy, the recalibration of Stripe 82, and implications on Galactic archaeology

In this contribution, we first introduce a spectroscopy based Stellar Color Regression
(SCR) method to perform accurate colour calibration for modern imaging surveys,
taking advantage of millions of stellar spectra now available.
The method is straightforward, model-free, applicable to regions
that are effectively covered by spectroscopic surveys,
and capable of delivering an accuracy of 1 mmag for colour calibration.
As an illustration, we have applied the method to the SDSS Stripe 82 data and
shown that the method has achieved a calibration accuracy of about 5 mmag in u-g,
3 mmag in g-r, and 2 mmag in r-i and i-z, respectively.
Using the re-calibrated Stripe 82 photometry, we explore the metallicity dependence
and intrinsic widths of the SDSS color loci. We find that the intrinsic widths of the loci
defined by both single main sequence stars and red giant stars are at maximum of a few mmag.
Implications of the metallicity-dependent stellar loci on demographical studies of
both the Galactic disk(s) and halo(s) are discussed.