A Photometric Metallicity Estimate of the Virgo Stellar Overdensity

TL;DR

This study estimates the metallicity of the Virgo Overdensity using photometric data from SDSS gri filters, finding it similar to field halo stars and demonstrating the method's potential for distant stellar populations.

Contribution

It introduces a calibration method for photometric metallicity estimates of main-sequence stars using gri filters, enabling studies beyond 10 kpc.

Findings

VOD metallicity estimated at [Fe/H] = -2.0 +/-0.1 (internal) +/-0.5 (systematic)

Method applied to 0.7 million stars in the Northern Galactic hemisphere

VOD metallicity indistinguishable from field halo stars within Delta [Fe/H] < 0.2

Abstract

We determine photometric metal abundance estimates for individual main-sequence stars in the Virgo Overdensity (VOD), which covers almost 1000 deg^2 on the sky, based on a calibration of the metallicity sensitivity of stellar isochrones in the gri filter passbands using field stars with well-determined spectroscopic metal abundances. Despite the low precision of the method for individual stars, we derive [Fe/H] = -2.0 +/-0.1 (internal) +/-0.5 (systematic) for the metal abundance of the VOD from photometric measurements of 0.7 million stars in the Northern Galactic hemisphere with heliocentric distances from ~10 kpc to ~20 kpc. The metallicity of the VOD is indistinguishable, within Delta [Fe/H] < 0.2, from that of field halo stars covering the same distance range. This initial application suggests that the SDSS gri passbands can be used to probe the properties of main-sequence stars beyond ~10 kpc, complementing studies of nearby stars from more metallicity-sensitive color indices that involve the u passband.