THREE-DIMENSIONAL SHOCK STRUCTURE OF THE ORION KL OUTFLOW WITH IGRINS

• Published in: The Astrophysical journal 2016-12, Vol.833 (2), p.275
• Main Authors: Oh, Heeyoung, Pyo, Tae-Soo, Kaplan, Kyle, Yuk, In-Soo, Park, Byeong-Gon, Mace, Gregory, Park, Chan, Chun, Moo-Young, Pak, Soojong, Kim, Kang-Min, Oh, Jae Sok, Jeong, Ueejeong, Yu, Young Sam, Lee, Jae-Joon, Kim, Hwihyun, Hwang, Narae, Lee, Hye-In, Le, Huynh Anh Nguyen, Lee, Sungho, Jaffe, Daniel T.
• Format: Article
• Language: English
• Subjects: Astrophysics; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DENSITY; DETECTION; DISTANCE; DISTRIBUTION; EMISSION; EXPLOSIONS; Extinction; Gratings (spectra); HYDROGEN; INCLINATION; Inclination angle; Molecular clouds; MOLECULES; Orion nebula; Outflow; PROPER MOTION; RADIAL VELOCITY; RED SHIFT; RESOLUTION; SHOCK WAVES; Slits; STARS; STREAMS; Submerging; THREE-DIMENSIONAL CALCULATIONS; Velocity; Velocity gradient
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/833/2/275

We report a study of the three-dimensional (3D) outflow structure of a 15″ × 13″ area around the H 2 peak 1 in Orion KL with slit-scan observations (13 slits) using the Immersion Grating Infrared Spectrograph. The datacubes have a high-velocity resolution (∼7.5 km s −1 ), provide high-contrast imaging within ultra-narrow bands, and enable the detection of the main stream of the previously reported H 2 outflow fingers. We identified 31 distinct fingers in the H 2 1−0 S(1) λ 2.122 μ m emission. The line profile at each finger shows multiple-velocity peaks with a strong low-velocity component around the systemic velocity at = +8 km s −1 and high-velocity emission ( = 45–135 km s −1 ), indicating a typical bow-shock. The observed radial velocity gradients of ∼4 km s −1 arcsec −1 agree well with the velocities inferred from large-scale proper motions, where the projected motion is proportional to the distance from a common origin. We construct a conceptual 3D map of the fingers with estimated inclination angles of 57°–74°. The extinction difference (Δ A v  > 10 mag) between blueshifted and redshifted fingers indicates high internal extinction. The extinction, the overall angular spread, and the scale of the flow argue for an ambient medium with a very high density (10 5 –10 6 cm −3 ), consistent with molecular line observations of the Orion Molecular Cloud core. The radial velocity gradients and the 3D distributions of the fingers together support the hypothesis of a simultaneous radial explosion of the Orion KL outflow.