2002ApJ...574..805U

We report the detection of a ringlike H I structure toward l=90°.0, b=2°.8, with a velocity of v_LSR=-99 km.s^–1. This velocity implies a distance of d=13 kpc, corresponding to a Galactocentric radius of R_gal=15kpc. The l-v_LSR diagram implies an expansion velocity of v_exp≃15 km.s^–1 for the shell. The structure has an oblate, irregular shell-like appearance, which surrounds weak infrared emission as seen in the 60 µm Infrared Astronomical Satellite data. At a distance of 13 kpc the size of the object is about 110x220 pc and placed 500 pc above the Galactic plane, with a mass of 10⁵ M_☉. An expanding shell with such a high mass and diameter cannot be explained by a single supernova explosion or by a single stellar wind bubble. We interpret the structure as a relic of a distant stellar activity region powered by the joint action of strong stellar winds from early-type stars and supernova explosions.