A Wide-area VLA Continuum Survey near the Galactic Center at 6 and 20 cm Wavelengths

TL;DR

This VLA survey near the Galactic center at 6 and 20 cm revealed new nonthermal filaments, polarized emissions, and compact sources, providing insights into the region's magnetic structures and interstellar medium effects.

Contribution

The survey provides the first polarization detections of several nonthermal filaments and extends the observed latitude range of these features, offering new data on Galactic center structures.

Findings

Detection of 8 nonthermal filaments in polarized emission, 3 of which are first-time detections.

Identification of a filament at high latitude, extending the known range of such features.

Evidence of spectral index gradients and potential electron scattering effects on compact source fluxes.

Abstract

We describe the results of a mJy-sensitivity, VLA survey of roughly 1 square degree near the Galactic center at 6 and 20 cm. Catalogs of compact and filamentary structures are given and compared to previous surveys of the region. Eight of the unusual, nonthermal radio filaments are detected in 6 cm polarized emission; three of these are the first such detections, confirming their nonthermal nature. This survey found emission from a filament at (l,b)=(359.1,0.75), or a projected distance from Sgr A* of 200 pc, greatly extending the latitude range observed with such features. There is also new evidence for spatial gradients in the 6/20 cm spectral indices of some filaments and we discuss models for these gradients. In studying compact sources, the combination of spectral index and polarization information allows us to identify pulsar candidates and compact HII regions in the survey. There is also some evidence that the flux measurements of compact sources may be affected by electron scattering from the interstellar medium in the cent ral few hundred parsecs of the Galaxy.