Photometric Metallicity Calibration with SDSS and SCUSS and its Application to distant stars in the South Galactic Cap

TL;DR

This paper develops a photometric calibration method using SDSS and SCUSS data to estimate stellar metallicity from colors, enabling studies of distant stars' metallicity distribution in the South Galactic Cap.

Contribution

The study introduces a new photometric calibration for metallicity estimation using SDSS and SCUSS data, extending the analysis to faint, distant stars up to g=21 magnitude.

Findings

Calibration achieves 0.14-0.16 dex accuracy in metallicity residuals.

Application to the Sagittarius stream reveals a broad metallicity distribution.

Halo stars are modeled with two Gaussian peaks at [Fe/H] = -1.9 and -1.5.

Abstract

Based on SDSS g, r and SCUSS (South Galactic Cap of u-band Sky Survey) $u$ photometry, we develop a photometric calibration for estimating the stellar metallicity from $u-g$ and $g-r$ colors by using the SDSS spectra of 32,542 F- and G-type main sequence stars, which cover almost $3700$ deg$^{2}$ in the south Galactic cap. The rms scatter of the photometric metallicity residuals relative to spectrum-based metallicity is $0.14$ dex when $g-r<0.4$, and $0.16$ dex when $g-r>0.4$. Due to the deeper and more accurate magnitude of SCUSS $u$ band, the estimate can be used up to the faint magnitude of $g=21$. This application range of photometric metallicity calibration is wide enough so that it can be used to study metallicity distribution of distant stars. In this study, we select the Sagittarius (Sgr) stream and its neighboring field halo stars in south Galactic cap to study their metallicity distribution. We find that the Sgr stream at the cylindrical Galactocentric coordinate of $R\sim 19$ kpc, $\left| z\right| \sim 14$ kpc exhibits a relative rich metallicity distribution, and the neighboring field halo stars in our studied fields can be modeled by two-Gaussian model, with peaks respectively at [Fe/H]$=-1.9$ and [Fe/H]$=-1.5$.