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

Studies of Galactic H <ns0:sc>II</ns0:sc> regions are of crucial importance for studying star formation and the evolution of the interstellar medium. Gaining an insight into their physical characteristics contributes to a more comprehensive understanding of these phenomena. The GLOSTAR project aims to provide a GLObal view on STAR formation in the Milky Way by performing an unbiased and sensitive survey. This is achieved by using the extremely wideband (4–8 GHz) C-band receiver of the Karl G. Jansky Very Large Array and the Effelsberg 100 m telescope. Using radio recombination lines observed in the GLOSTAR survey with the VLA in D-configuration with a typical line sensitivity of 1 σ ~ 3.0 mJy beam−1 at ~5 km s−1 and an angular resolution of 25″, we cataloged 244 individual Galactic H <ns0:sc>II</ns0:sc> regions (−2° ≤ ℓ ≤ 60° and |b| ≤ 1°, and 76° ≤ ℓ ≤ 83° and −1° ≤ b ≤ 2°) and derived their physical properties. We examined the mid-infrared (MIR) morphology of these H <ns0:sc>II</ns0:sc> regions and find that a significant portion of them exhibit a bubble-like morphology in the GLIMPSE 8 μm emission. We also searched for associations with the dust continuum and sources of methanol maser emission, other tracers of young stellar objects, and find that 48% and 14% of our H <ns0:sc>II</ns0:sc> regions, respectively, are coextensive with those. We measured the electron temperature for a large sample of H <ns0:sc>II</ns0:sc> regions within Galactocentric distances spanning from 1.6 to 13.1 kpc and derived the Galactic electron temperature gradient as ~372 ± 28 K kpc−1 with an intercept of 4248 ± 161 K, which is consistent with previous studies.