Spatially resolved 74 MHz absorption toward the galactic center region

Abstract

We present the highest resolution Very Large Array 74 MHz images of a ~ 10 degree field centered on the Galactic center to date. In addition to giving an unprecedented view of the extended nonthermal emission surrounding the Galactic center, the 74 MHz image shows deep free-free absorption across the Galactic center itself, as well as, to the NE of SgrA. We show that this absorption is due to intermediate density and temperature ionized gas in front of the nonthermal Galactic center (GC) emission, at least some of which appears to be associated with the GC itself. The morphology, nature, and relationship to the Galactic center of the 74 MHz absorption will be discussed. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Basic research in radio astronomy at the Naval Research Laboratory is supported by the Office of Naval Research.