Gaia: Orion's Integral Shaped Filament is a Standing Wave

Understand

The Integral Shaped Filament (ISF) is the nearest molecular cloud with rapid star formation, including massive stars, and it is therefore a star-formation laboratory.

• We use Gaia parallaxes, to show that the distances to young Class II stars ('disks') projected along the spine of this filament are related to the gas radial velocity by $$ v = -{D\over\tau} + K;\qquad \tau = 4\,{\rm Myr}, $$ where $K$ is a constant.
• This implies that the ISF is a standing wave, which is consistent with the Stutz & Gould (2016) 'Slingshot' prediction.
• The $\tau=4\,{\rm Myr}$ timescale is consistent with the 'Slingshot' picture that the Orion Nebula Cluster (ONC) is the third cluster to be violently split off from the Orion A cloud (following NGC 1981 and NGC 1987) at few-Myr intervals due to gravito-magnetic oscillations.