Hypercalibration: A Pan-STARRS1-based recalibration of the Sloan Digital Sky Survey

TL;DR

This paper introduces a recalibration of SDSS photometry using Pan-STARRS1 data, significantly improving photometric accuracy and identifying non-photometric periods, thereby enhancing the reliability of SDSS measurements.

Contribution

It provides a new recalibration method for SDSS photometry based on PS1 data, achieving millimagnitude precision and identifying transient non-photometric periods.

Findings

Achieved RMS residuals of 3 mmag in $griz$ bands and 15 mmag in $u$ band.

Recalibrated SDSS and PS1 photometry with RMS differences of 7-9 mmag.

Identified transient non-photometric periods ('contrails') in SDSS data.

Abstract

We present a recalibration of the Sloan Digital Sky Survey (SDSS) photometry with new flat fields and zero points derived from Pan-STARRS1 (PS1). Using PSF photometry of 60 million stars with $16 < r < 20$, we derive a model of amplifier gain and flat-field corrections with per-run RMS residuals of 3 millimagnitudes (mmag) in $griz$ bands and 15 mmag in $u$ band. The new photometric zero points are adjusted to leave the median in the Galactic North unchanged for compatibility with previous SDSS work. We also identify transient non-photometric periods in SDSS ("contrails") based on photometric deviations co-temporal in SDSS bands. The recalibrated stellar PSF photometry of SDSS and PS1 has an RMS difference of {9,7,7,8} mmag in $griz$, respectively, when averaged over $15'$ regions.