A Discussion of the Distribution of Interstellar Matter Close to the Sun
Abstract
Summary. Using the new data of Radhakrishnan et al. (1972) and of Hughes, Thompson and Colvin (1971), the distribution and kinematics of the interstellar clouds and of the hot intercloud medium are discussed separately. As shown by Radhakrishnan et al., the equivalent thickness of the cloud system close to the Sun is 330 pc, and its mean density at z =0 is 0.29 atom cm 3. The velocity dispersion between the clouds is shown to be isotropic and equal to 6.4+0.9km s ' Using the displacement of the line profiles of the intercloud medium due to differential rotation, we show that the equivalent thickness of the intercloud medium is 585+ 100pc; its density at z=0 is 0. assuming a gaussian shape for the z-distribution. The equivalent thickness of the disk of interstellar thermal electrons is found to be of the order of 1 kpc or more, from a discussion of the dispersion, Faraday rotation and interstellar scintillation of pulsars and extragalactic radiosources; this thickness is consistent with ionization of the intercloud medium by a uniform and steady flux of low-energy cosmic rays or soft X-rays. Key words: interstellar matter - Galactic structure - pulsars - 21 cm radiation - scintillations
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 1973
- Bibcode:
- 1973A&A....25..253F