Radio study of the Arc and the Sgr A complex near the Galactic center

TL;DR

This radio study of the galactic center reveals complex thermal and nonthermal structures, including filaments and arcs, providing insights into their characteristics, organization, and relative positions near Sgr A.

Contribution

The paper provides detailed radio observations of the galactic center, identifying and characterizing various filamentary structures and their properties, which enhances understanding of the region's magnetic and thermal environment.

Findings

Identification of nonthermal filaments with polarized emission

Thermal nature of arched filamentary structures

Relative positioning of Sgr A East and West

Abstract

Radio continuum and radio recombination line observations of the inner degree of the galactic center reveal a rich collection of thermal and nonthermal radio structures: (a) A network of linear filaments that are oriented perpendicular to the galactic plane constitute the major portion of the radio Arc at l~ 0.2{\deg}. These filaments have nonthermal characteristics, show polarized emission at 6, 3 and 2 cm, are organized over a 100 pc scale, and have a flat spectrum. (b) A number of thread-like filaments are situated asymmetrical with respect to the galactic plane and appear to be isolated unlike the linear filaments which are grouped together. The polarization and spectra of these so called "threads" are not yet known. (c) A network of arched filamentary structures that is disorganized in its appearance constitutes the curved portion of the Arc. Radio recombination line emission from these filaments indicates a thermal character for the emission. (d) A very steep-spectrum ridge of emission is seen to emerge from Sgr A. (e) The relative location of Sgr A East, West, a cluster of HII regions and the 50 km/s molecular cloud are discussed. Comparisons of the low and high-frequency maps show clearly that Sgr A East lies behind Sgr A West.