Letter to the Editor

Local spiral structure based on the Gaia EDR3 parallaxes^⋆

¹ Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210023, PR China
e-mail: xuye@pmo.ac.cn
² School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, PR China
³ National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100101, PR China
⁴ College of Science, China Three Gorges University, Yichang 443002, PR China
⁵ CAS Key Laboratory of FAST, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, PR China

Received: 10 December 2020
Accepted: 30 December 2020

Abstract

Context. The astrometric satellite Gaia is expected to significantly increase our knowledge as to the properties of the Milky Way. The Gaia Early Data Release 3 (EDR3) provides the most precise parallaxes for many OB stars, which can be used to delineate the Galactic spiral structure.

Aims. We investigate the local spiral structure with the largest sample of spectroscopically confirmed young OB stars available to date, and we compare it with what was traced by the parallax measurements of masers.

Methods. A sample consisting of three different groups of massive young stars, including O–B2 stars, O–B0 stars and O-type stars with parallax accuracies better than 10% was compiled and used in our analysis.

Results. The local spiral structures in all four Galactic quadrants within ≈5 kpc of the Sun are clearly delineated in detail. The revealed Galactic spiral pattern outlines a clear sketch of nearby spiral arms, especially in the third and fourth quadrants where the maser parallax data are still absent. These O-type stars densify and extend the spiral structure constructed by using the Very Long Baseline Interferometry maser data alone. The clumped distribution of O-type stars also indicates that the Galaxy spiral structure is inhomogeneous.