Aperture synthesis observations of the 21 centimeter Zeeman effect toward Cassiopeia A

Abstract

view Abstract Citations (38) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Aperture Synthesis Observations of the 21 Centimeter Zeeman Effect toward Cassiopeia A Schwarz, U. J. ; Troland, T. H. ; Albinson, J. S. ; Bregman, J. D. ; Goss, W. M. ; Heiles, Carl Abstract The Westerbork synthesis radio telescope has been used to perform an improved sensitivity study of the 21 cm H I Zeeman effect toward Cas A. Synthesis maps of the line-of-sight magnetic field strength are presented for velocities corresponding to the Perseus arm absorption features. Considerable spatial structure exists in these maps, with measured field strengths exceeding 40 micro-G at some positions in front of the source. No significant reversals in field direction are apparent. Peaks in magnetic field strength often coincide in position with clumps of molecular gas that appear in H2CO and in OH synthesis maps of Cas A. The magnetic field peaks arise in clumps of higher density H I gas that are associated with the molecular clumps. Thus, for the first time, an increase in magnetic field strength with interstellar gas density. Magnetic effects are likely to have an important influence upon the dynamics of the H I clumps and to a lesser extent upon the molecular clumps. High magnetic fields in the direction of Cas A may arise because the line of sight passes through, or close to, regions of star formation. Publication: The Astrophysical Journal Pub Date: February 1986 DOI: 10.1086/163902 Bibcode: 1986ApJ...301..320S Keywords: Cassiopeia Constellation; Interstellar Gas; Interstellar Magnetic Fields; Nebulae; Radio Sources (Astronomy); Supernova Remnants; Zeeman Effect; Astronomical Maps; Hydrogen Clouds; Molecular Clouds; Synthetic Apertures; Astrophysics; INTERSTELLAR: MAGNETIC FIELDS; NEBULAE: INDIVIDUAL NAME: CASSIOPEIA A; NEBULAE: SUPERNOVA REMNANTS; RADIO SOURCES: 21 CM RADIATION; ZEEMAN EFFECT full text sources ADS | data products SIMBAD (2)