Stellar Loci. IX. Estimation of Stellar Parameters from CSST-like Photometry

TL;DR

This paper develops two methods to estimate stellar parameters from CSST-like photometry, demonstrating high precision and potential for large-scale stellar characterization using upcoming space telescope data.

Contribution

It introduces novel techniques for simultaneously estimating metallicity and surface gravity, and classifying giants and dwarfs from CSST-like photometry, validated with theoretical and observational data.

Findings

Achieves ~0.088 dex precision for metallicity with theoretical data

Attains ~0.39 dex precision for log g with observational data

Effectively distinguishes giants from dwarfs, especially for red or metal-poor giants

Abstract

The China Space Station Telescope (CSST) will conduct a deep and wide imaging survey in the NUV-, u-, g-, r-, i-, z-, and y-bands. In this work, using theoretical data synthesized from the BOSZ spectra of Bohlin et al. (2017), along with observational data constructed from different sources, we present two methods for estimating stellar parameters from CSST-like photometry. One approach is to estimate metallicity [M/H] and surface gravity log g simultaneously by using the metallicity- and log g-dependent stellar loci. Tests with theoretical data (without photometric errors) result in precisions of 0.088 dex and 0.083 dex for [M/H] and log g, respectively. With 0.01 mag photometric errors, precision is degraded by about a factor of two, due to degeneracy in [M/H] and log g. Tests with observational data, although with larger photometric errors, result in precisions of 0.10 dex and 0.39 dex for [Fe/H] and log g, respectively, thanks to the strong correlation between stellar colors and log g in real data. The other approach is the giant-dwarf loci method to obtain classifications and metallicity estimates. With the same observational data, it achieves a better [Fe/H] precision of 0.084 dex, due to the stronger constraints imposed on log g. The method also performs well in distinguishing giants from dwarfs, particularly for red or metal-poor giants. This work demonstrates the clear potential of the CSST data, paving the way for stellar-parameter estimates for many billions of stars.