2015/06/02 by Soumavo Ghosh, Chanda J. Jog · 24 citations
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Barred spiral galaxy #Classical mechanics #Density wave theory #Dispersion relation #Elliptical galaxy #Galaxies: Formation, Evolution, Phenomena #Galaxy #Grand design spiral galaxy #Lenticular galaxy #Optics #Physics #Spiral (railway) #Spiral galaxy #Stars #Stellar, planetary, and galactic studies #Velocity dispersion #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stv1040
published in Monthly Notices of the Royal Astronomical Society 451(2), 1350-1355 (Oxford University Press) · 6 pages, 3 figures, 1 table, accepted for publication in MNRAS
arxiv created 2015/06/02 · openalex publication_date 2015/06/04 · arxiv updated 2016/01/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The density wave theory for the grand-design two-armed spiral pattern in galaxies is successful in explaining several observed features. However, the long-term persistence of this spiral structure is a serious problem since the group transport would destroy it within about a billion years as shown in a classic paper by Toomre. In this paper, we include the low-velocity dispersion component, namely gas, on an equal footing with stars in the formulation of the density wave theory, and obtain the dispersion relation for this coupled system. We show that the inclusion of gas makes the group transport slower by a factor of few, thus allowing the pattern to persist longer – for several billion years. Though still less than the Hubble time, this helps in making the spiral structure more long-lived. Further we show that addition of gas is essential to get a stable wave for the observed pattern speed for the Galaxy, which otherwise is not possible for a one-component stellar disc.