Dynamical models and Galaxy surveys

TL;DR

This paper discusses how equilibrium dynamical models of the Galaxy can be tested with survey data prior to knowing the survey's selection function, using the RAVE, GCS, and SEGUE surveys to illustrate the approach.

Contribution

It introduces a method to test dynamical models against survey data before the survey's selection function is known, extending models to include chemistry and applying them to real survey data.

Findings

Predicted [Fe/H] distribution differs from observed, indicating potential issues with abundance scales.

Extended models successfully incorporate chemistry and dynamics to match survey data.

Identifies discrepancies in metallicity distributions that are likely due to abundance scale issues.

Abstract

Equilibrium dynamical models are essential tools for extracting science from surveys of our Galaxy. We show how models can be tested with data from a survey before the survey's selection function has been determined. We illustrate the application of this method by presenting some results for the RAVE survey. We extend our published analytic distribution functions to include chemistry and fit the chosen functional form to a combination of the Geneva--Copenhagen survey (GCS) and a sample of G-dwarfs observed at z~1.75 kpc by the SEGUE survey. By including solid dynamics we are able to predict the contribution that the thick disc/halo stars surveyed by SEGUE should make to the GCS survey. We show that the measured [Fe/H] distribution from the GCS includes many fewer stars at [Fe/H]<-0.6 than are predicted. The problem is more likely to lie in discordant abundance scales than with incorrect dynamics.