A 20 centimeter survey of the Galactic center region. I. Detection of numerous linear filaments

This is the first in a series of papers presenting a sensitive 20 cm VLA continuum survey of the Galactic center region using new and archival data based on multiconfiguration observations taken with relatively uniform uv coverage. The high dynamic range images cover the regions within -2° < l " 5° and 40' < b < 40' with a spatial resolution of ≈30″ and 10″. The wide field imaging technique is used to construct a low-resolution mosaic of 40 overlapping pointings. The mosaic image includes the Effelsburg observations filling the low spatial frequency uv data. We also present high-resolution images of 23 overlapping fields using DnC and CnB array configurations. These high-resolution images are sensitive to both compact and extended continuum features with a wide range of angular scales with rms noise of 0.2 mJy beam ^-1 in the outer parts of the Galactic center region. The survey has resulted in a catalog of 345 discrete sources as well as 140 images revealing structural details of H n regions, supernova remnants, pulsar wind nebulae, and more than 80 linear filaments distributed toward the complex region of the Galactic center. These observations show the evidence for an order-of-magnitude increase in the number of faint linear filaments with typical lengths of a few arcminutes. Many of the filaments show morphological characteristics similar to the Galactic center nonthermal radio filaments (NRFs). The linear filaments are not isolated but are generally clustered in star-forming regions where prominent NRFs had been detected previously. The extensions of many of these linear filaments appear to terminate at either a compact source or a resolved shell-like thermal source. A relationship between the filaments, the compact and extended thermal sources, as well as a lack of preferred orientation for many RFs should constrain models that are proposed to explain the origin of nonthermal radio filaments in the Galactic center.