The galactic plane region near $\mathsf{\ell=93^\circ}$

Abstract

We present new Canadian Galactic Plane Survey radio continuum and 21 cm HI line observations of NRAO 655 (G93.4+1.8), plus radio recombination line observations, and optical H -line observations. The radio spectrum of NRAO 655 conrms its emission as thermal. From the 21 cm HI data we nd an atomic hydrogen cavity associated with this object atv' 71: 5k m s 1 . The cavity corresponds in position and size to the brightest radio continuum emission from NRAO 655. The corresponding kinematic distance is 8.8 kpc, placing NRAO 655 in the Perseus Arm. NRAO 655's linear size is therefore 70 pc 130 pc. To conrm the21 cm HI velocity we present the rst recombination line detection of NRAO 655 (H158 line, v' 71 km s 1 ), and the rst observations of a molecular cloud coinciding with NRAO 655 (at v' 72 km s 1 ). The rst optical detection of 656 nm H emission line features in NRAO 655 is also presented, and the H emission line brightness is determined. We suggest that the eastward extension of this strongly asymmetric object originates in a champagne outflow, and we estimate its age. We show that a single early-type star cannot be responsible for the outflow, whereas a group of later-type stars would suce. A partial HI shell is seen adjacent to the brightest part of NRAO 655; we suggest that it has been formed by dissociation of H2 in the molecular cloud.