The global spiral structure of M81 - Radio continuum maps

Abstract

view Abstract Citations (34) References (31) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Global Structure of M81: Radio Continuum Maps Bash, Frank N. ; Kaufman, Michele Abstract VLA observations of the radio continuum emission from M81 at wavelengths of 6 and 20 cm are presented and used to check the predictions of density-wave theories. Both thermal and nonthermal radiation are detected from the spiral arms. On maps with a resolution of 10arcsec - 15arcsec, the authors separate giant H II regions from the more extended, nonthermal arm emission and find that most of the bright knots along the radio arms are giant radio H II regions. The nonthermal emission defines spiral arms that are patchy and well-resolved, with a width of 1 - 2 kpc. The observed arm widths appear consistent with the predictions of density-wave models that emphasize the clumpy nature of the interstellar medium. The 20 cm arms appear to spiral outward from a faint inner H I ring. At large R the radio continuum arms are approximately logarithmic spirals although the two arms differ in pitch angle. Publication: The Astrophysical Journal Pub Date: November 1986 DOI: 10.1086/164715 Bibcode: 1986ApJ...310..621B Keywords: Continuous Spectra; Density Wave Model; Galactic Structure; Radio Astronomy; Spiral Galaxies; Centimeter Waves; H Ii Regions; Linear Polarization; Nonthermal Radiation; Radiant Flux Density; Astrophysics; GALAXIES: INDIVIDUAL MESSIER NUMBER: M81; GALAXIES: STRUCTURE; NEBULAE: H II REGIONS; POLARIZATION; RADIO SOURCES: GALAXIES full text sources ADS | data products SIMBAD (6) NED (6)