Photometric recalibration of the SDSS Stripe 82 to a few milimagnitude
  precision with the stellar color regression method and Gaia EDR3
  By combining spectroscopic data from the LAMOST DR7, SDSS DR12, and corrected
photometric data from the Gaia EDR3, we apply the Stellar Color Regression
(SCR; Yuan et al. 2015a) method to recalibrate the SDSS Stripe 82 standard
stars catalog of Ivezi\'c et al. (2007). With a total number of about 30,000
spectroscopically targeted stars, we have mapped out the relatively large and
strongly correlated photometric zero-point errors present in the catalog,
$\sim$2.5 per cent in the $u$ band and $\sim$ 1 per cent in the $griz$ bands.
Our study also confirms some small but significant magnitude dependence errors
in the $z$ band for some charge-coupled devices. Various tests show that we
have achieved an internal precision of about 5 mmag in the $u$ band and about 2
mmag in the $griz$ bands, which is about 5 times better than previous results.
We also apply the method to the latest version of the catalog (V4.2; Thanjavur
et al. 2021), and find modest systematic calibration errors up to $\sim$ 1 per
cent along the R.A. direction and smaller errors along the Dec. direction. The
results demonstrate the power of the SCR method when combining spectroscopic
data and Gaia photometry in breaking the 1 percent precision barrier of
ground-based photometric surveys. Our work paves the way for the re-calibration
of the whole SDSS photometric survey and has important implications for the
calibration of future surveys. Future implementations and improvements of the
SCR method under different situations are also discussed.
