The Alma catalog of OB stars. II. A cross-match with Gaia DR2 and an updated map of the solar neighbourhood

TL;DR

This study cross-matched the Alma OB star catalog with Gaia DR2 data to create a comprehensive, accurate map of massive stars in the solar neighborhood, revealing a new Galactic structure and its implications for star formation.

Contribution

It provides the first detailed cross-match of OB stars with Gaia DR2, analyzes their 3D distribution, and identifies a new Galactic structure called the Cepheus spur linked to star formation.

Findings

Identification of the Cepheus spur structure.

Gaia DR2 distances are robust across different priors.

The Cepheus spur is likely related to the Radcliffe wave.

Abstract

We cross-match the Alma catalog of OB stars with Gaia DR2 astrometry and photometry as a first step towards producing a clean sample of massive stars in the solar neighbourhood with a high degree of completeness. We analyze the resulting colour-absolute magnitude diagram to divide our sample into categories and compare extinction estimates from two sources, finding problems with both of them. The distances obtained with three different priors are found to have few differences among them, indicating that Gaia DR2 distances are robust. An analysis of the 3-D distribution of massive stars in the solar neighbourhood is presented. We show that a kinematically distinct structure we dub the Cepheus spur extends from the Orion-Cygnus spiral arm towards the Perseus arm and is located above the Galactic mid-plane, likely being related to the recently discovered Radcliffe wave. We propose that this corrugation pattern in the Galactic disk may be responsible for the recent enhanced star formation at its crests and troughs. We also discuss our plans to extend this work in the immediate future.