3D shape of Orion A from Gaia DR2

  • Josefa E. Grossschedl
  • , Joao Alves
  • , Stefan Meingast
  • , Christine Ackerl
  • , Joana Ascenso
  • , Herve Bouy
  • , Andreas Burkert
  • , Jan Forbrich
  • , Verena Fuernkranz
  • , Alyssa Goodman
  • , Alvaro Hacar
  • , Gabor Herbst-Kiss
  • , Charles J. Lada
  • , Irati Larreina
  • , Kieran Leschinski
  • , Marco Lombardi
  • , Andre Moitinho
  • , Daniel Mortimer
  • , Eleonora Zari

Research output: Contribution to journalArticlepeer-review

121 Citations (Scopus)
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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.
Original languageEnglish
Article numberA106
Number of pages9
JournalAstronomy & Astrophysics
Volume619
Early online date14 Nov 2018
DOIs
Publication statusE-pub ahead of print - 14 Nov 2018

Keywords

  • Local insterstellar matter
  • Methods: Observational
  • Methods: Statistical
  • Parallaxes
  • Stars: Distances
  • Stars: Formation

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