The halo shape and evolution of polar disc galaxies

O. N. Snaith, B. K. Gibson, C. B. Brook, A. Knebe, R. J. Thacker, T. R. Quinn, F. Governato, P. B. Tissera

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

We examine the properties and evolution of a simulated polar disc galaxy. This galaxy is composed of two orthogonal discs, one of which contains old stars (old stellar disc) and the other both younger stars and cold gas (polar disc). By exploring the shape of the inner region of the dark matter halo, we are able to confirm that the halo shape is an oblate ellipsoid flattened in the direction of the polar disc. We also note that there is a twist in the shape profile, where the innermost 3kpc of the halo flattens in the direction perpendicular to the old disc and then aligns with the polar disc out until the virial radius. This result is then compared to the halo shape inferred from the circular velocities of the two discs. We also use the temporal information of the simulation to track the system's evolution and identify the processes which give rise to this unusual galaxy type. We confirm the proposal that the polar disc galaxy is the result of the last major merger, where the angular moment of the interaction is orthogonal to the angle of the infalling gas. This merger is followed by the resumption of coherent gas infall. We emphasize that the disc is rapidly restored after the major merger and that after this event the galaxy begins to tilt. A significant proportion of the infalling gas comes from filaments. This infalling gas from the filament gives the gas its angular momentum, and, in the case of the polar disc galaxy, the direction of the gas filament does not change before or after the last major merger.

Original languageEnglish
Pages (from-to)1967-1979
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Volume425
Issue number3
DOIs
Publication statusPublished - 21 Sep 2012

Keywords

  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: haloes
  • Galaxies: interactions
  • Galaxies: structure

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Fingerprint

Dive into the research topics of 'The halo shape and evolution of polar disc galaxies'. Together they form a unique fingerprint.

Cite this