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The Radcliffe wave is a ∼3 kpc long coherent gas structure containing most of the star-forming complexes near the Sun. In this Letter we aim to find a Galactic context for the Radcliffe wave by looking into a possible relationship between the gas structure and the Orion (local) arm. We use catalogs of massive stars and young open clusters based on Gaia Early Data Release 3 (EDR3) astrometry, in conjunction with kiloparsec-scale 3D dust maps, to investigate the Galactic XY spatial distributions of gas and young stars. We find a quasi-parallel offset between the luminous blue stars and the Radcliffe wave, in that massive stars and clusters are found essentially inside and downstream from the Radcliffe wave. We examine this offset in the context of color gradients observed in the spiral arms of external galaxies, where the interplay between density wave theory, spiral shocks, and triggered star formation has been used to interpret this particular arrangement of gas and dust as well as OB stars, and outline other potential explanations as well. We hypothesize that the Radcliffe wave constitutes the gas reservoir of the Orion (local) arm, and that it presents itself as a prime laboratory to study the interface between Galactic structure, the formation of molecular clouds in the Milky Way, and star formation.
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Mapping luminous hot stars in the Galaxy
Luminous hot stars ( M K s ≲ 0 mag and T eff ≳ 8000 K) dominate the stellar energy input to the interstellar medium throughout cosmological time, are used as laboratories to test theories of stellar evolution and multiplicity, and serve as luminous tracers of star formation in the Milky Way and other galaxies. Massive stars occupy well-defined loci in colour–colour and colour–magnitude spaces, enabling selection based on the combination of Gaia EDR3 astrometry and photometry and 2MASS photometry, even in the presence of substantive dust extinction. In this paper we devise an all-sky sample of such luminous OBA-type stars, which was designed to be complete rather than very pure, providing targets for spectroscopic follow-up with the SDSS-V survey. To estimate the purity and completeness of our catalogue, we derive stellar parameters for the stars in common with LAMOST DR6 and we compare the sample to other O and B-type star catalogues. We estimate ‘astro-kinematic’ distances by combining parallaxes and proper motions with a model for the expected velocity and density distribution of young stars; we show that this adds useful constraints on the distances and therefore luminosities of the stars. With these distances we map the spatial distribution of a more stringently selected subsample across the Galactic disc, and find it to be highly structured, with distinct over- and under-densities. The most evident over-densities can be associated with the presumed spiral arms of the Milky Way, in particular the Sagittarius-Carina and Scutum-Centaurus arms. Yet, the spatial picture of the Milky Way’s young disc structure emerging in this study is complex, and suggests that most young stars in our Galaxy ( t age < t dyn ) are not neatly organised into distinct spiral arms. The combination of the comprehensive spectroscopy to come from SDSS-V (yielding velocities, ages, etc.) with future Gaia data releases will be crucial in order to reveal the dynamical nature of the spiral arms themselves.
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- Award ID(s):
- 2034429
- PAR ID:
- 10298458
- Date Published:
- Journal Name:
- Astronomy & Astrophysics
- Volume:
- 650
- ISSN:
- 0004-6361
- Page Range / eLocation ID:
- A112
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1051/0004-6361/202039726
