The Aquila Supershell: A Remnant of Multiple Supernovae

A large area surrounding the Aquila Supershell (GS 034-06+65) was mapped in the H I 21 cm emission line. The new data show that the structure consists of an irregular spherical shell about 5°.6 in diameter, which extends 9°.5 below the Galactic plane, and of a well-defined, massive cone at low latitudes, which connects to a molecular cloud in the Galactic plane through a narrow (20 pc wide) channel of reduced H I emission. The system probably lies at a distance of ∼3.3 kpc, which implies that the shell has a diameter of ∼320 pc and extends at least 550 pc into the Galactic halo. We estimate that the swept-up mass in the shell is 6.0 x 104 Msun and the mass in the cone is 1.8 x 105 Msun. The concentration of supernova remnants, star-forming regions, and H II regions in this direction implies that the Aquila Supershell is a remnant of multiple supernovae and that star formation activity persists in this region of the Galaxy. We estimate that the total energy of the events creating the remnant is (1-5) x 1052 ergs, which corresponds to 10-100 supernova explosions powering the system in 107 yr. It is possible that the W48 complex of H II regions has resulted from star formation induced by a shock wave related to the cone.