NIHAO VI. The hidden discs of simulated galaxies

Aura Obreja, Gregory S. Stinson, Aaron A. Dutton, Andrea V. Macciò, Liang Wang, Xi Kang

Research output: Contribution to journalArticle

Abstract

Detailed studies of galaxy formation require clear definitions of the structural components of galaxies. Precisely defined components also enable better comparisons between observations and simulations. We use a subsample of 18 cosmological zoom-in simulations from the Numerical Investigation of a Hundred Astrophysical Objects (NIHAO) project to derive a robust method for defining stellar kinematic discs in galaxies. Our method uses Gaussian Mixture Models in a 3D space of dynamical variables. The NIHAO galaxies have the right stellar mass for their halo mass, and their angular momenta and Sérsic indices match observations. While the photometric disc-to-total ratios are close to 1 for all the simulated galaxies, the kinematic ratios are around ~0.5. Thus, exponential structure does not imply a cold kinematic disc. Above M* ~ 109.5 M, the decomposition leads to thin discs and spheroids that have clearly different properties, in terms of angular momentum, rotational support, ellipticity, [Fe/H] and [O/Fe]. At M* ≲ 109.5 M, the decomposition selects discs and spheroids with less distinct properties. At these low masses, both the discs and spheroids have exponential profiles with high minor-to-major axes ratios, i.e. thickened discs.

Original languageEnglish (US)
Pages (from-to)467-486
Number of pages20
JournalMonthly Notices of the Royal Astronomical Society
Volume459
Issue number1
DOIs
StatePublished - Jun 11 2016

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Keywords

  • Galaxies: fundamental parameters
  • Galaxies: kinematics and dynamics
  • Galaxies: stellar content
  • Galaxies: structure
  • Methods: numerical

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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