Three-Dimensional Distribution of the ISM in the Milky Way Galaxy: I. The H I Disk
Abstract
We derived the three-dimensional distribution of H I gas in the Milky Way Galaxy using the latest H I survey data cubes and rotation curves. The distance of the H I gas was determined by the kinematic distance using a rotation curve. We solved the near-far problem in the inner Galaxy by a fitting method which involves introducing a model of vertical H I distribution. In our resultant maps we could trace three prominent arms: the Sagittarius-Carina arm, the Perseus arm, and the Outer arm. These three arms were found to be logarithmic spiral arms. The pitch angles of the Sagittarius-Carina, Perseus, and Outer arms were estimated to be about 11°, 18°, and 7°, respectively. The Sun is located in a region rich in H I gas between the Sagittarius-Carina arm and the Perseus arm. The H I disk shows large and asymmetric warping in the outer disk: the H I disk goes up to about 1.5kpc above the Galactic plane in the northern hemisphere, and down to about 1kpc in the southern hemisphere, which means asymmetric warping. The inner H I disk is also found to be tilting. The radius of the H I disk is about 17kpc and the H I mass within this radius is estimated to be 2.5 × 109 M⊙, which corresponds to 1.5% of the dynamical mass predicted from the rotation curve. We also found that the H I outskirt is largely swelling in the fourth quadrant, and hence the Galaxy is significantly lopsided. The scale-height of the H I layer increases with the radius, and is correlated with the H I volume density at the centroid of the H I layer.
- Publication:
-
Publications of the Astronomical Society of Japan
- Pub Date:
- February 2003
- DOI:
- 10.1093/pasj/55.1.191
- arXiv:
- arXiv:astro-ph/0304338
- Bibcode:
- 2003PASJ...55..191N
- Keywords:
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- Galaxy: disk;
- Galaxy: kinematics and dynamics;
- Galaxy: structure;
- ISM: kinematics and dynamics;
- radio lines: ISM;
- Astrophysics
- E-Print:
- 14 pages, 13 figures