The interaction of a large-scale nuclear wind with the high velocity HII region G0.17+0.15

Abstract

We investigate the nature of a Galactic center source, G0.17+0.15, lying along the northern extension of the Radio Arc near l ~ 0.2°. G0.17+0.15 is an HII region located toward the eastern edge of the radio bubble, embedded within the highly polarized Galactic center eastern Lobe where a number of radio filaments appear to cross through the HII region. We report the detection of hydrogen and helium recombination lines with a radial velocity exceeding 140 km s⁻¹ based on GBT and VLA observations. The morphology of G0.17+0.15, aided by kinematics, and spectral index characteristics, suggests the presence of an external pressure dragging and shredding the ionized gas. We argue that this ionized cloud is interacting with a bundle of radio filaments and is entrained by the ram pressure of the radio bubble, which itself is thought to be produced by cosmic-ray driven outflows at the Galactic center. In this interpretation, the gas streamers on the western side of G0.17+0.15 are stripped, accelerated from 0 to δv ~ 35 km s⁻¹ over a time scale roughly 8 × 10⁴ years, implying that ablating ram pressure is ~700 eV cm⁻³, comparable to the ~10³ eVcm⁻³ cosmic-ray driven wind pressure in the Galactic center region.