Spiral density waves in M81. I. Stellar spiral density waves

Chien Chang Feng, Lien Hsuan Lin, Hsiang Hsu Wang, Ronald E. Taam

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

Aside from the grand-design stellar spirals appearing in the disk of M81, a pair of stellar spiral arms situated well inside the bright bulge of M81 has been recently discovered by Kendall et al. The seemingly unrelated pairs of spirals pose a challenge to the theory of spiral density waves. To address this problem, we have constructed a three-component model for M81, including the contributions from a stellar disk, a bulge, and a dark matter halo subject to observational constraints. Given this basic state for M81, a modal approach is applied to search for the discrete unstable spiral modes that may provide an understanding for the existence of both spiral arms. It is found that the apparently separated inner and outer spirals can be interpreted as a single trailing spiral mode. In particular, these spirals share the same pattern speed 25.5 km s-1 kpc-1 with a corotation radius of 9.03 kpc. In addition to the good agreement between the calculated and the observed spiral pattern, the variation of the spiral amplitude can also be naturally reproduced.

Original languageEnglish (US)
Article number103
JournalAstrophysical Journal
Volume785
Issue number2
DOIs
StatePublished - Apr 20 2014

Keywords

  • galaxies: individual (M81)
  • galaxies: spiral
  • methods: analytical
  • waves

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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