Spiral structure of M51 - Displacement of the H I from the nonthermal radio arms

Abstract

view Abstract Citations (67) References (10) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spiral Structure of M51: Displacement of the H i from the Nonthermal Radio Arms Tilanus, R. P. J. ; Allen, R. J. Abstract The neutral atomic hydrogen (H I) in the grand design spiral galaxy M51 has been observed with the Westerbork Synthesis Radio Telescope at a resolution of 12" x 18" and compared with other tracers of spiral structure: the dust lanes, the H II regions, and especially the nonthermal radio continuum emission. Over major sections of the inner spiral arms, the H I ridge is parallel to the ridge of nonthermal radio continuum but not coincident with it. The H I ridge is displaced to larger radii by about 200 pc in a segment of the northern arm of 450 pc over a large segment of the southern arm. We have earlier observed this phenomenon in portions of the spiral arms of M83. The present results confirm that the displacement of the H I arms from the region of maximum compression of the interstellar gas in not an isolated peculiarity of one particular galaxy. We present a simple picture which describes the observations in the framework of density-wave streaming of the interstellar gas. This picture was proposed earlier to account for the same phenomenon which we observed in M83. Presuming that the nonthermal continuum ridge traces the locus of maximum density of the interstellar gas, the observations are consistent with the view that most of the H I in the inner spiral arms of M51 is a product of the dissociation of predominantly molecular gas by the star-formation process. Publication: The Astrophysical Journal Pub Date: April 1989 DOI: 10.1086/185419 Bibcode: 1989ApJ...339L..57T Keywords: Extragalactic Radio Sources; Galactic Structure; H I Regions; Interstellar Matter; Spiral Galaxies; Continuous Radiation; H Ii Regions; Radio Emission; Radio Telescopes; Astrophysics; GALAXIES: INDIVIDUAL MESSIER NUMBER: M51; GALAXIES: INTERSTELLAR MATTER; GALAXIES: STRUCTURE; RADIO SOURCES: GALAXIES full text sources ADS | data products SIMBAD (2) NED (2)