Three-Dimensional Aquila Rift: Magnetized HI Arch Anchored by Molecular Complex

Abstract

Three dimensional structure of the Aquila Rift of magnetized neutral gas is investigated by analyzing HI and CO line data. The projected distance on the Galactic plane of the HI arch of the Rift is ~250 pc from the Sun. The HI arch emerges at l~ 30 deg, reaches to altitudes as high as ~ 500 pc above the plane at l~ 350deg, and returns to the disk at l~270 deg. The extent of arch at positive latitudes is ~1 kpc and radius is ~100 pc. The eastern root is associated with the giant molecular cloud complex, which is the main body of the optically defined Aquila Rift. The HI and molecular masses of the Rift are estimated to be M_HI~1.4x10^5Msun and M_H2 ~3x10^5 Msun. Gravitational energies to lift the gases to their heights are E_grav: HI ~1.4x10^51 and E_grav: H_2 ~0.3x10^51 erg, respectively. Magnetic field is aligned along the HI arch of the Rift, and the strength is measured to be B~10 microG using Faraday rotation measures of extragalactic radio sources. The magnetic energy is estimated to be E_mag~1.2x10^51 erg. A possible mechanism of formation of the Aquila Rift is proposed in terms of interstellar magnetic inflation by a sinusoidal Parker instability of wavelength of ~2.5 kpc and amplitude ~500 pc.