3D shape of Orion A from Gaia DR2
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.
Full Table B.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/619/A106- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 2018
- DOI:
- 10.1051/0004-6361/201833901
- arXiv:
- arXiv:1808.05952
- Bibcode:
- 2018A&A...619A.106G
- Keywords:
-
- methods: statistical;
- methods: observational;
- parallaxes;
- stars: distances;
- stars: formation;
- local insterstellar matter;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 9 pages, 5 figures, 4 tables, accepted for publication in A&