A comparison of high-resolution radio and optical data for the northeast region of the Cygnus Loop

• Published in: The Astrophysical journal Vol. 306; no. 1; pp. 266 - 270
• Main Authors: Straka, W. C., Dickel, J. R., Blair, W. P., Fesen, R. A.
• Format: Journal Article
• Language: English
• Published: Legacy CDMS University of Chicago Press 01.07.1986
• Subjects: Astronomy; Astrophysics; Earth, ocean, space; Exact sciences and technology; Interstellar medium (ism) and nebulae in milky way; Stellar systems. Galactic and extragalactic objects and systems. The universe; Supernova remnants; Interstellar loop; Models; Radio interferometric observation; Structure; Cygnus loop
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/164340

Radio observations of the northeastern part of the Cygnus Loop obtained with the VLA at 18 cm with a resolution of 4.7 arcsec are presented and discussed. In general, the brightest radio filaments match the brightest optical filaments very well, particularly those which are bright in H-alpha. The agreement in position, morphology, and relative brightness is particularly good where all four optical species are bright. However, a few bright radio features have no bright optical counterparts. The general radio and optical structure of the region can be explained by a model in which shocked interstellar clouds form filaments due to unstable cooling and compression. The features appear to be ropelike, although it is not possible to rule out that they are irregular sheets seen edge-on. A large gradation in cooling on a scale of parsecs is evidenced by the sequence of the optical species in emission, with a corresponding increase in density generally evidenced by the continuum radio emission.