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Position-Velocity Diagrams as a Probe of the Bar in Edge-On Galaxies

Published online by Cambridge University Press:  25 May 2016

Keiichi Wada
Affiliation:
Center for Information Processing Education, Hokkaido Univ., Sapporo 060, Japan
Tetsuo Hasegawa
Affiliation:
Institute of Astronomy, The Univ. of Tokyo, Mitaka, Tokyo 181, Japan
Yoshiaki Sofue
Affiliation:
Institute of Astronomy, The Univ. of Tokyo, Mitaka, Tokyo 181, Japan
Yoshiaki Taniguchi
Affiliation:
Astronomical Institute, Tohoku Univ., Sendai 980-77, Japan
Asao Habe
Affiliation:
Dep. of Physics, Hokkaido Univ., Sapporo 060, Japan

Extract

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Analyses of the distribution of far infrared point sources in the Galactic bulge have suggested that from a face-on perspective the bulge has a bar like shape. Here, we investigate how a rotating bar-like bulge affects the global gas dynamics in a disk and compare the longitude-velocity (LV) maps from selfgravitating hydrodynamical simulations with observed maps of neutral hydrogen and carbon monoxide in the Galaxy. We found that the features on the numerical LV maps depend strongly on four factors: the pattern speed of the bar, the position angle of the Sun, the strength of the bar potential and the ratio of the gas mass to total dynamical mass. We conclude that our Galaxy has a rotating, weak, bar-like bulge (a/b ∼ 0.8) observed from nearly end on (θp < 20°). The allowed range of pattern speed of the bar is surprisingly narrow (∼ 20 km s–1 kpc–1) and is consistent with recent observations of bulge stars. Selfgravity of the interstellar matter is needed to account for some of the observations.

Type
Chapter 2: Is the Milky Way a Barred Spiral Galaxy?
Copyright
Copyright © Kluwer 1996 

References

Wada, K. & Habe, A. 1992 MNRAS, 258, 82.CrossRefGoogle Scholar
Sofue, Y. & Nakai, N. 1993, PASJ, 45, 139.Google Scholar
Block, D.L., & Wainscoat, R.J. 1991, Nature, 353, 48.CrossRefGoogle Scholar