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

Abstract

ABSTRACT We investigate the nature of a Galactic Centre source, G0.17+0.15, lying along the northern extension of the radio arc near l ∼ 0.2°. G0.17+0.15 is an H ii region located towards the eastern edge of the radio bubble, embedded within the highly polarized Galactic Centre eastern lobe where a number of radio filaments appear to cross through the H ii region. We report the detection of hydrogen and helium recombination lines with a radial velocity exceeding 140 km s−1 based on Green Bank Telescope and Very Large Array 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 Centre. In this interpretation, the gas streamers on the western side of G0.17+0.15 are stripped, accelerated from 0 to $\delta v\sim \, 35$ km s−1 over a time-scale roughly 8 × 104 yr, implying that ablating ram pressure is $\sim 700\, \mathrm{eV\, cm^{-3}}$, comparable to the $\sim 10^3\, \mathrm{eV \, cm^{-3}}$ cosmic ray driven wind pressure in the Galactic Centre region.