Year: 2026
Type: article
Abstract: We explore the three-dimensional structure of a sample of ∼16,000 young giant stars in the Galactic disk out to ∼8 kpc in heliocentric distance. This population traces a thin disk with a local vertical scale height of h Z ⊙ = 74 ± 5 pc, which progressively thickens toward the outer Galaxy with a prominent Galactic flare, rising exponentially with a radial scale length of h fl = 3.5 ± 0.4 kpc. Our analysis incorporates both the survey selection function and the vertical displacements caused by the Galactic warp and corrugations, which, if neglected, would lead to significant biases in the derived disk scale height. In the Galactic plane, the young giants trace coherent spiral arm segments, extending previous maps based on upper main sequence (UMS) and OB stars by 2–4 kpc, depending on the considered direction. The obtained map supports a pitch angle of roughly 20° for the Perseus Arm, and shows that the Local/Orion Arm stretches at least 10 kpc in length. Unlike earlier and more local maps based on UMS and OB stars, where the relatively small sampled portion of the Perseus Arm appeared as a short, nearly straight feature, our map reveals it as an extended structure with a gentle curvature, as expected for spiral arms on large scales. In the inner Galaxy, we also identify a new segment likely associated with the Scutum Arm, clearly detached from the Sagittarius-Carina Arm in the fourth Galactic quadrant.
Source: The Astrophysical Journal
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
OpenAlex ID: W7221782820