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 journalArticlepeer-review

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

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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