GBT19B-334

A Multi-Wavelength Radio Analysis of the Inner-Galaxy Diffuse Ionized Gas

Abstract

Diffuse ionized gas (DIG) is a low-density, ~10^4K plasma prevalent in Milky Way-like galaxies. Although the DIG is a major component of the interstellar medium (ISM), there remain major unanswered questions regarding its origin and physical characteristics. Because of the significance of the DIG within the ISM, these open questions imply that we do not truly understand the ISM itself. Here we propose to observe several directions toward the inner-Galaxy DIG, which are uncontaminated by emission from discrete HII regions, in radio recombination line (RRL) emission using the 342 and 800MHz Prime Focus receivers. Since the intensity of hydrogen RRLs as a function of frequency is determined by the physical properties of the emitting gas, comparisons of RRL observations at different frequencies allow us to constrain these properties with minimal assumptions. We will combine our low-frequency RRL data with data at higher frequencies (4-8GHz) from the recently completed GDIGS project (AGBT17B-173, AGBT18B-014). Our observations will allow us to: 1) derive the electron density and electron temperature of the inner-Galaxy DIG, 2) constrain the 3-dimensional structure of the emitting plasma, 3) quantify the impact of turbulence in the DIG, and 4) constrain the origin of the DIG near the Galactic plane.

Investigators

Name	Institution
Matteo Luisi *	Westminster College
Pedro Salas	Green Bank Observatory
Loren Anderson	West Virginia University
Kimberly Emig	National Radio Astronomy Observatory

* indicates the PI