MaGICC Thick Disk I: Comparing a Simulated Disk Formed with Stellar Feedback to the Milky Way

We analyse the structure and chemical enrichment of a Milky Way-like galaxy with a stellar mass of 2 × 1010 M�, formed in a cosmological hydrodynamical simulation. It is disc dominated with a flat rotation curve, and has a disc scalelength similar to the Milky Way’s, but a velocity dispersion that is ̃50 per cent higher. Examining stars in narrow [Fe/H] and [�/Fe] abundance ranges, we find remarkable qualitative agreement between this simulation and observations. (a) The old stars lie in a thickened distribution with a short scalelength, while the young stars form a thinner disc, with scalelengths decreasing, as [Fe/H] increases. (b) Consequently, there is a distinct outward metallicity gradient. (c) Mono-abundance populations exist with a continuous distribution of scaleheights (from thin to thick). However, the simulated galaxy has a distinct and substantive very thick disc (hz ̃ 1.5 kpc), not seen in the Milky Way. The broad agreement between simulations and observations allows us to test the validity of observational proxies used in the literature: we find in the simulation that mono-abundance populations are good proxies for single age populations (<1 Gyr) for most abundances. DOI: https://doi.org/10.1093/mnras/stt1600 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-90744 Accepted Version Originally published at: Stinson, G S; Bovy, J; Rix, H W; Brook, C; Roskar, R; Dalcanton, J J; Maccio, A V; Wadsley, J; Couchman, H M P; Quinn, T R (2013). MaGICC thick disc I. Comparing a simulated disc formed with stellar feedback to the Milky Way. Monthly Notices of the Royal Astronomical Society, 436(1):625-634. DOI: https://doi.org/10.1093/mnras/stt1600 ar X iv :1 30 1. 53 18 v2 [ as tr oph .G A ] 1 O ct 2 01 3 Mon. Not. R. Astron. Soc. 000, 000–000 (0000) Printed 2 October 2013 (MN LTEX style file v2.2) MaGICC Thick Disk I: Comparing a Simulated Disk Formed with Stellar Feedback to the Milky Way G. S. Stinson, J. Bovy, H-W Rix, C. Brook , R. Roškar, J. J. Dalcanton, A. V. Macciò, J. Wadsley, H. M. P. Couchman, T. R. Quinn Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540, USA Departamento de F́ıśıca Teórica, Universidad Autónoma de Madrid, E-28049 Cantoblanco, Madrid, Spain Institut für Theoretische Physik, Universität Zürich, Switzerland Astronomy Department, University of Washington, Box 351580, Seattle, WA, 98195-1580 Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, L8S 4M1, Canada Hubble Fellow