On the Spiral Structure of the Milky Way Galaxy - Astrophysics > Cosmology and Nongalactic AstrophysicsReport as inadecuate




On the Spiral Structure of the Milky Way Galaxy - Astrophysics > Cosmology and Nongalactic Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We consider the possible pattern of the overall spiral structure of theGalaxy, using data on the distribution of neutral atomic, molecular, andionized hydrogen, on the base of the hypothesis of the spiral structure beingsymmetric, i.e. the assumption that spiral arms are translated into each otherfor a rotation around the galactic center by 180{\deg} a two-arm pattern orby 90{\deg} a four-arm pattern. We demonstrate that, for the inner region,the observations are best represented with a four-arm scheme of the spiralpattern, associated with all-Galaxy spiral density waves. The basic position isthat of the Carina arm, reliably determined from distances to HII regions andfrom HI and H2 radial velocities. This pattern is continued in the quadrantsIII and IV with weak outer HI arms; from their morphology, the Galaxy should beconsidered an asymmetric multi-arm spiral. The kneed shape of the outer armsthat consist of straight segments can indicate that these arms are transientformations that appeared due to a gravitational instability in the gas disk.The distances between HI superclouds in the two arms that are the brightest inneutral hydrogen, the Carina arm and the Cygnus Outer arm, concentrate to twovalues, permitting to assume the presence of a regular magnetic field in thesearms.



Author: Yuri N.Efremov

Source: https://arxiv.org/







Related documents