Lick Indices in the Thin and Thick Disks of Edge‐On Disk Galaxies

2008/05/27 by Peter Yoachim, Julianne J. Dalcanton
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Enhanced Data Rates for GSM Evolution #Galaxies: Formation, Evolution, Phenomena #Galaxy #Luminosity #Metallicity #Physics #Stars #Stellar, planetary, and galactic studies #Thick disk #Thin disk #astro-ph

paper · pdf · doi:10.1086/590246

14 pages, 10 figures, accepted for publication in ApJ

arxiv created 2008/05/27 · openalex publication_date 2008/08/19 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

We have measured Lick index equivalent widths to derive luminosity weighted stellar ages and metallicities for thin- and thick-disk-dominated regions of nine edge-on disk galaxies with the ARC 3.5 m telescope at Apache Point Observatory. In all cases, the thick disks are confirmed to be old stellar populations, with typical ages between 4 and 10 Gyr. The thin disks are uniformly younger than the thick disks, and show strong radial age gradients, with the outer regions of the disks being younger than 1 Gyr. We do not detect any significant metallicity differences or α-element enhancement in the thick-disk stars compared to the thin disk, due to the insensitivity of the Lick indices to these differences at low metallicity. We compare these results to thick disks measured in other systems and to predictions from thick-disk formation models.

Citations

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Cited by

• On the Radial Metallicity Gradient and Radial Migration Effect of the Galactic Disk