A new method to determine the thickness of non-edge-on disk galaxies

Abstract

Aims. We present a new method to determine the thickness of non-edge-on disk galaxies. This method allows us to investigate the mass-to-light ratio of the disk. Methods. Our method is based on the comparison of observations and theory of the distribution of the vertical velocity dispersion, which is obtained from the solution of three dimensional Poisson equations and the galactic dynamical equation. Results. As examples, the thickness and mass-to-light ratio of two disk galaxies, NGC 1566 and NGC 5247, which have been extensively studied by spectroscopy, have been calculated. The calculated results are consistent with observations and support the use of this method. However, due to the small sample size available, the results should be confirmed on other samples of galaxies.

Global gravitationally organized spiral waves and the structure of NGC 5247

“…Our numerical modelling is based on photometric data taken by Zhao, Peng & Hu (). We take as the radial scalelength of the disc r d = 4.8 kpc, as determined by these authors.…”

“…The inclination angle of NGC 5247 is rather uncertain. Measurements range from i = 20° (Zhao et al ) to i = 40° (HyperLeda; Paturel et al ). In this paper we adopt an inclination of 28°, which is close to an average from these references, and a distance to the galaxy of 17.4 Mpc (HyperLeda; Paturel et al ).…”

“…Unfortunately, an accurate estimate of the vertical thickness of the galactic disc is not simple. Zhao et al () tackled this problem by using the Jeans equations applied along the vertical axis of the disc and estimated the disc thickness of NGC 5247 to be z 0 = 1.5 ± 0.6 kpc. With this value, the ratio of the radial to vertical scalelength is .…”

“…Kruit and Freeman (1986), open squares -measurements of Bottema (1993). Zhao et al (2006) tackled this problem by using the Jeans equations applied along the vertical axis of the disk, and estimated the disk thickness of NGC 5247 to be z0 = 1.5±0.6 kpc. With this value, the ratio of the radial to vertical scale length is r d /z0 = 3.2 +2.1 −0.9 .…”

Measurements of the equivalent thicknesses of three-dimensional spiral galactic disks

“…The thickness data for over 100 galaxies have been acquired by processing the spiral galactic images using Peng's improved method. Zhao et al (2006) presented a new method to determine the thickness of non-edge-on spiral galaxies by using the solution of the Jeans equation along the z-direction. In this work, the new thickness data of 42 spiral galactic disks are calculated by dealing with the sixth release of spiral galactic images from the Sloan Digital Sky Survey (SDSS).…”