The Gaia-ESO Survey: the selection function of the Milky Way field stars

TL;DR

The paper details the target selection process of the Gaia-ESO Survey for Milky Way field stars, emphasizing how understanding selection effects is crucial for accurate analysis of Galactic stellar populations.

Contribution

It introduces the methodology and weights for target selection in the Gaia-ESO Survey, enabling correction for selection biases in Galactic studies.

Findings

Provided detailed target selection criteria and weights

Highlighted importance of accounting for selection effects

Demonstrated how weights influence stellar population analysis

Abstract

The Gaia-ESO Survey was designed to target all major Galactic components (i.e., bulge, thin and thick discs, halo and clusters), with the goal of constraining the chemical and dynamical evolution of the Milky Way. This paper presents the methodology and considerations that drive the selection of the targeted, allocated and successfully observed Milky Way field stars. The detailed understanding of the survey construction, specifically the influence of target selection criteria on observed Milky Way field stars is required in order to analyse and interpret the survey data correctly. We present the target selection process for the Milky Way field stars observed with VLT/FLAMES and provide the weights that characterise the survey target selection. The weights can be used to account for the selection effects in the Gaia-ESO Survey data for scientific studies. We provide a couple of simple examples to highlight the necessity of including such information in studies of the stellar populations in the Milky Way.