An [$\alpha$/Fe]-enhanced thick disk in a Milky Way Analogue

TL;DR

This study uses VLT-MUSE observations to identify alpha-rich and alpha-poor stellar populations in a Milky Way-like galaxy, suggesting external galaxies also have distinct disk components, informing galaxy formation models.

Contribution

First detection of chemically distinct thick and thin disk components in an external Milky Way-like galaxy using integral field spectroscopy.

Findings

External galaxy UGC 10738 has alpha-rich and alpha-poor populations.

Spatial distributions of these populations are similar to the Milky Way.

Implications for galaxy formation theories and disk component origins.

Abstract

The Milky Way disk consists of two prominent components - a thick, alpha-rich, low-metallicity component and a thin, metal-rich, low-alpha component. External galaxies have been shown to contain thin and thick disk components, but whether distinct components in the [$\alpha$/Fe]-[Z/H] plane exist in other Milky Way-like galaxies is not yet known. We present VLT-MUSE observations of UGC 10738, a nearby, edge-on Milky Way-like galaxy. We demonstrate through stellar population synthesis model fitting that UGC 10738 contains alpha-rich and alpha-poor stellar populations with similar spatial distributions to the same components in the Milky Way. We discuss how the finding that external galaxies also contain chemically distinct disk components may act as a significant constraint on the formation of the Milky Way's own thin and thick disk.