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

X. Galactic H II region catalog using radio recombination lines^★

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
e-mail: skhan@mpifr-bonn.mpg.de
² Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
³ National Radio Astronomy Observatory, PO Box O, 1003 Lopezville Road, Socorro, NM 87801, USA
⁴ Centre for Astrophysics and Planetary Science, University of Kent, Canterbury CT2 7NH, UK
⁵ National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, Chaoyang District, Beijing 100101, PR China
⁶ Key Laboratory of Radio Astronomy and Technology, Chinese Academy of Sciences, A20 Datun Road, Chaoyang District, Beijing 100101, PR China
⁷ German Aerospace Center, Scientific Information, 51147 Cologne, Germany
⁸ Instituto Nacional de Astrofísica, Óptica y Electrónica, Apartado Postal 51 y 216, 72000 Puebla, Mexico
⁹ Department of Earth & Space Sciences, Indian Institute of Space Science and Technology, Trivandrum 695547, India
¹⁰ Max Planck Institute for Astronomy, Koenigstuhl 17, 69117 Heidelberg, Germany
¹¹ I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
¹² Department of Physics, Indian Institute of Science, Bangalore 560012, India

Received: 30 January 2024
Accepted: 2 July 2024

Abstract

Studies of Galactic H II 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 II 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 II 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 II regions, respectively, are coextensive with those. We measured the electron temperature for a large sample of H II 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.