The magnetic field structure of the CMa R1 star formation region

The CMa R1 association is embedded in a curved region of dark and reflection nebulosity which is part of a larger-scale ring structure of emission nebulosity thought to be a relatively old supernova remnant (Herbst and Assousa 1977, 1978), These investigators and Herbst, Racine, and Warner (1978) have argued that recent star formation in CMa R1 was induced by the supernova. Indeed, data for the emission ring, an associated expanding HI shell, and a nearby runaway star infer an age for the supernova remnant of 3x10 5 years; consistent with the age of most of the CMa R1 stars.