Structure of the Hinear the Northeast Limb of the Cygnus Loop

Abstract

Observations of the 21 cm neutral hydrogen line of the northeastern part of the Cygnus Loop have been made with the Dominion Radio Astrophysical Observatory's Synthesis Telescope and the 26 m telescope. The northeast rim has a region almost free of confusing bright structures, allowing analysis of the velocity structure of the smoothly distributed H I near the limb. Spectral line maps in 128 channels with 1.65 km s-1 velocity separation were constructed for the region. The kinematic and positional data are evidence for a cloud of atomic material in the form of an expanding partial shell adjacent to the northeast limb of the Cygnus Loop. The partial shell is of relatively high density (4 cm-3), is expanding at 6 km s-1 with a velocity dispersion of 3 km s-1, is thick (~3 pc), and has a mass of ~8 M☉. Possible origins of the shell are discussed.