J/A+A/619/A106 3D shape of Orion A from Gaia DR2 (Grossschedl+, 2018)
3D shape of Orion A from Gaia DR2.
Grossschedl J.E., Alves J., Meingast S., Ackerl C., Ascenso J., Bouy H.,
Burkert A., Forbrich J., Fuernkranz V., Goodman A., Hacar A.,
Herbst-Kiss G., Lada C.J., Larreina I., Leschinski K., Lombardi M.,
Moitinho A., Mortimer D., Zari E.
<Astron. Astrophys. 619, A106 (2018)>
=2018A&A...619A.106G 2018A&A...619A.106G (SIMBAD/NED BibCode)
ADC_Keywords: Parallaxes, trigonometric ; YSOs ; Stars, distances ;
Stars, pre-main sequence ; Interstellar medium
Keywords: stars: formation - stars: distances - molecular cloud: Orion A -
astrometry: parallaxes
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 ∼75pc long Tail.
The true extent of Orion A is not the projected ∼40pc but ∼90pc,
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.
Description:
Catalog of the 682 YSOs, used to infer on the cloud's shape. We use
Gaia DR2 parallaxes of these YSOs, which can be used as a good proxy
for cloud distances in Orion A.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tableb1.dat 89 682 YSO sample
--------------------------------------------------------------------------------
See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: tableb1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- Source The Gaia DR2 source id (1)
21- 37 F17.14 deg RAdeg Right ascension (ICRS at Ep=2015.5)
39- 56 F18.14 deg DEdeg Declination (ICRS at Ep=2015.5)
58- 71 F14.12 mas Plx The Gaia DR2 parallax (1)
73- 86 F14.12 mas e_Plx The Gaia DR2 parallax error (1)
88- 89 A2 --- Class [II F] YSO class taken from Grossschedl
et al., 2018, A&A, accepted (VISION III) (2)
--------------------------------------------------------------------------------
Note (1): Further Gaia parameters can be obtained at the Gaia Archive
(https://gea.esac.esa.int/archive/), using the Gaia DR2 source_id for
cross-matching, or at CDS, Cat. I/345.
Note (2): YSO classification as follows:
II = Class II
F = flat-spectrum source
--------------------------------------------------------------------------------
Acknowledgements:
Josefa Grossschedl, josefa.elisabeth.grossschedl(at)univie.ac.at,
josefa.groszschedl(at)gmail.com
Joao Alves, joao.alves(at)univie.ac.at
(End) J. Grossschedl [Univ. Wien, Austria], P. Vannier [CDS] 15-Nov-2018