We use the Gaia DR2 distances of about 700 mid-infrared selected young stellar objects in the benchmark giant molecular cloud Orion A to infer its 3D shape and orientation. We find that Orion A is not the fairly straight filamentary cloud that we see in (2D) projection, but instead a cometary-like cloud oriented toward the Galactic plane, with two distinct components: A denser and enhanced star-forming (bent) Head, and a lower density and star-formation quieter ∼75 pc long Tail. The true extent of Orion A is not the projected ∼40 pc but ∼90 pc, making it by far the largest molecular cloud in the local neighborhood. Its aspect ratio (∼30:1) and high column-density fraction (∼45%) make it similar to large-scale Milky Way filaments ("bones"), despite its distance to the galactic mid-plane being an order of magnitude larger than typically found for these structures.

3D shape of Orion A from Gaia DR2 / J.E. Großschedl, J. Alves, S. Meingast, C. Ackerl, J. Ascenso, H. Bouy, A. Burkert, J. Forbrich, V. Fürnkranz, A. Goodman, Á. Hacar, G. Herbst-Kiss, C.J. Lada, I. Larreina, K. Leschinski, M. Lombardi, A. Moitinho, D. Mortimer, E. Zari. - In: ASTRONOMY & ASTROPHYSICS. - ISSN 0004-6361. - 619(2018 Nov 14). [10.1051/0004-6361/201833901]

3D shape of Orion A from Gaia DR2

M. Lombardi;E. Zari
Ultimo
2018

Abstract

We use the Gaia DR2 distances of about 700 mid-infrared selected young stellar objects in the benchmark giant molecular cloud Orion A to infer its 3D shape and orientation. We find that Orion A is not the fairly straight filamentary cloud that we see in (2D) projection, but instead a cometary-like cloud oriented toward the Galactic plane, with two distinct components: A denser and enhanced star-forming (bent) Head, and a lower density and star-formation quieter ∼75 pc long Tail. The true extent of Orion A is not the projected ∼40 pc but ∼90 pc, making it by far the largest molecular cloud in the local neighborhood. Its aspect ratio (∼30:1) and high column-density fraction (∼45%) make it similar to large-scale Milky Way filaments ("bones"), despite its distance to the galactic mid-plane being an order of magnitude larger than typically found for these structures.
Local insterstellar matter; Methods: Observational; Methods: Statistical; Parallaxes; Stars: Distances; Stars: Formation; Astronomy and Astrophysics; Space and Planetary Science
Settore FIS/05 - Astronomia e Astrofisica
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/619879
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