Probing Galactic Structure with the Spatial Correlation Function of SEGUE G-dwarf Stars

TL;DR

This study uses the spatial correlation function of G-dwarf stars from SDSS SEGUE data to precisely measure the Milky Way's disk scale heights and lengths, revealing potential small-scale substructure.

Contribution

It provides new, precise constraints on the thin and thick disk parameters and uncovers evidence for small-scale substructure in the Galactic disk.

Findings

Precise measurements of thin- and thick-disk scale heights and lengths.

Detection of excess clustering at small scales (<50 pc).

Two-disk models are insufficient to explain all clustering features.

Abstract

We measure the two-point correlation function of G-dwarf stars within 1-3 kpc of the Sun in multiple lines-of-sight using the Schlesinger et al. G-dwarf sample from the SDSS SEGUE survey. The shapes of the correlation functions along individual SEGUE lines-of-sight depend sensitively on both the stellar-density gradients and the survey geometry. We fit smooth disk galaxy models to our SEGUE clustering measurements, and obtain strong constraints on the thin- and thick-disk components of the Milky Way. Specifically, we constrain the values of the thin- and thick-disk scale heights with 3% and 2% precision, respectively, and the values of the thin- and thick-disk scale lengths with 20% and 8% precision, respectively. Moreover, we find that a two-disk model is unable to fully explain our clustering measurements, which exhibit an excess of clustering at small scales (< 50 pc). This suggests the presence of small-scale substructure in the disk system of the Milky Way.