A 3D view of the outflow in the Orion Molecular Cloud 1 (OMC-1)

Abstract

Context. Stars whose mass is an order of magnitude greater than the Sun play a prominent role in the evolution of galaxies, exploding as supernovae, triggering bursts of star formation and spreading heavy elements about their host galaxies. A fundamental aspect of star formation is the creation of an outflow. The fast outflow emerging from a region associated with massive star formation in the Orion Molecular Cloud 1 (OMC-1), located behind the Orion Nebula, appears to have been set in motion by an explosive event. Aims. We study the structure and dynamics of outflows in OMC-1. We combine radial velocity and proper motion data for near-IR emission of molecular hydrogen to obtain the first 3-dimensional (3D) structure of the OMC-1 outflow. Our work illustrates a new diagnostic tool for studies of star formation that will be exploited in the near future with the advent of high spatial resolution spectro-imaging in particular with data from the Atacama Large Millimeter Array (ALMA). Methods. We used published radial and proper motion velocities obtained from the shock-excited vibrational emission in the H 2 v = 1−0 S(1) line at 2.122 μm obtained with the GriF instrument on the Canada-France-Hawaii Telescope, the Apache Point Observatory, the Anglo-Australian Observatory, and the Subaru Telescope. Results. These data give the 3D velocity of ejecta yielding a 3D reconstruction of the outflows. This allows one to view the material from different vantage points in space giving considerable insight into the geometry. Our analysis indicates that the ejection occurred < ∼ 720 years ago from a distorted ring-like structure of ∼15 (6000 AU) in diameter centered on the proposed point of close encounter of the stars BN, source I and maybe also source n. We propose a simple model involving curvature of shock trajectories in magnetic fields through which the origin of the explosion and the center defined by extrapolated proper motions of BN, I and n may be brought into spatial coincidence.

The complexity of Orion: an ALMA view

“…A number of works have revealed the H 2 and the 12 CO expansions linked to this explosion (e.g. Allen & Burton 1993;Zapata et al 2009;Nissen et al 2012;Youngblood et al 2016) but it seems that the interaction of this event with the surrounding cores has only been considered by Zapata et al (2011). While we will address in greater details the link we see between the explosion and a number of species peculiar velocity distributions (including nitrogen monoxide, isocyanic acid, vinyl and ethyl cyanide) in a forthcoming paper (Pagani et al, in prep.…”

Resolving the chemical substructure of Orion-KL

“…Presented as black contours overlaid on the 1.3 mm colourmap in the inner panel of Fig. 2, these 865 µm structures are: SMA1 (a high-mass protostellar source, suggested to be the driving source of the high-velocity outflow; Beuther & Nissen 2008), Source I (located at the centre of the SiO masers and believed to drive the bipolar low-velocity outflow; Menten & Reid 1995;Matthews et al 2010), Source N (a Herbig Ae/Be or mid-B star with a luminosity of ∼2000 L ; Menten & Reid 1995;Greenhill et al 2004;Gómez et al 2005;Rodríguez et al 2005;Goddi et al 2011b;Nissen et al 2012), and hotcore. Hereafter, we use "HC" to denote the whole region resolved by 1.3 mm continuum at a spatial resolution of ∼1200 AU, the "hotcore" to denote the position resolved by 865 µm continuum at a spatial resolution of ∼300 AU, and the "hot molecular core" to describe an evolutionary status.…”

A 1.3 cm line survey toward Orion KL

“…An extremely high kinetic temperature is also indicated by detections of high J metastable NH 3 transitions with energy levels up to 1900 K and a high rotational temperature of ∼400 K (Wilson et al 1993). The HC is believed to be heated by an explosive event (Bally et al 2011;Zapata et al 2011;Nissen et al 2012). Its line profiles have velocities of υ lsr ∼ 3−6 km s −1 and widths of Δυ ∼ 5−12 km s −1 ; (4) the "compact ridge" (CR) component.…”