A global view on star formation: The GLOSTAR Galactic plane survey

Abstract

Context. The GLObal view on STAR formation in the Milky Way (GLOSTAR) survey studies star formation with the Very Large Array (VLA) and the Effelsberg 100 meter radio telescope in the Galactic plane between ‑2° < ℓ < 60° and |b| < 1°, and the Cygnus X region (76° < ℓ < 83° and ‑1° < b < 2°), with unprecedented sensitivity in both flux density (1σ ~50 μJy beam‑1) and the capability of detecting emission with angular scales in the range from 1.″0 to the largest radio structures in the Galaxy on the order of a few degrees in size. Aims. Here, we provide a complete GLOSTAR-VLA D-configuration radio source catalog for the part of the Galactic disk covered. A catalog for the "pilot region" between 28° < ℓ < 36° has been published in a previous paper and here we present the complementary catalog for the area within 2° < ℓ < 28°, 36° < ℓ < 60° and |b| < 1°. Methods. Observations were taken with the VLA in a 4–8 GHz band to image 100 square degrees of the inner Galactic disk at a reference frequency of 5.8 GHz, using a total of 260 h of telescope time. We determined spectral indices (α; Sν ∝ να) inside the observed band and in the frequency range of 1.4–5.8 GHz by complementing our results with those from The HI/OH/Recombination line survey of the inner Milky Way (THOR), which covers 1–2 GHz. Results. The final images have an angular resolution of 18″ and an average sensitivity of 123 μJy beam‑1. The sensitivity is better (~60 μJy beam‑1) in areas free of extended emission. The complementary Galactic disk catalog presented in this work consists of 11 211 radio sources. Of these, 1965 are known large-scale structure sources such as star-forming region complexes, well-known supernova remnants (SNRs), SNR candidates, or parts thereof. The remaining 9227 are discrete individual sources. Source parameters–namely flux densities, sizes, spectral indices, and classifications-are reported. We identify 769 H II region candidates, 359 of which have been newly classified as such. The mean value of spectral indices of 225 H II regions is +0.14 ± 0.02, consistent with most of them emitting optically thin thermal radio emission. Combining our results with the previously published catalog of the pilot region, the final GLOSTAR-VLA D-configuration catalog contains 12 981 radio sources.