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

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.

8 pages, 5 figures, accepted for publication in ApJL

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• The survey of planetary nebulae in Andromeda (M 31) V. Chemical enrichment of the thin and thicker discs of Andromeda. Oxygen to argon abundance ratios for planetary nebulae and H II regions
• The imprint of clump formation at high redshift. II. The chemistry of the bulge
• The vertical structure of the spiral galaxy NGC 3501: first stages of the formation of a thin metal-rich disc
• The SAMI Survey: Evidence for dynamical coupling of ionised gas and young stellar populations