A rotating protostellar jet launched from the innermost disk of HH 212

Abstract

The central problem in forming a star is the angular momentum in the circumstellar disk which prevents material from falling into the central stellar core. An attractive solution to the "angular momentum problem" appears to be the ubiquitous (low-velocity and poorlycollimated) molecular outflows and (high-velocity and highly-collimated) protostellar jets accompanying the earliest phase of star formation that remove angular momentum at a range of disk radii 1 . Previous observations suggested that outflowing material carries away the excess angular momentum via magneto-centrifugally driven winds from the surfaces of circumstellar disks down to ∼ 10 AU scales 2-6 , allowing the material in the outer disk to transport to the inner disk. Here we show that highly collimated protostellar jets remove the residual angular momenta at the ∼ 0.05 AU scale, enabling the material in the innermost region of the disk to accrete toward the central protostar. This is supported by the rotation of the jet measured down to ∼ 10 AU from the protostar in the HH 212 protostellar sys-1

ALMA discovery of a rotating SO/SO2 flow in HH212

“…A DW model fit, with λ = 5.5 and W = 30 (see text), is overplotted in black for parameters denoted in each panel. Panels e−f : PV diagrams observed by Lee et al (2017a) across the SiO knots N2 and S3 (grayscale and black/red contours). Their measured centroids are shown as green squares and fitted rotation gradient as a black line.…”

“…The SO 2 (8 2,6 −7 1,7 ) line at 334.67335 GHz was observed with a spectral resolution of 1 km s Lee et al (2017a); the yellow ellipse marks the centrifugal barrier radius at r ∼ 45 au and the height of the COM-rich disk atmosphere at z ± 20 au (Lee et al 2017c). Images are rotated such that the vertical axis corresponds to the jet axis at PA = 22…”

“…Using ALMA observations with an 8 au beam, Lee et al (2017a) recently detected evidence for rotation in fast SiO jet knots from the HH212 protostar in the same sense as the rotating envelope. Assuming steady magneto-centrifugal launching and taking the observed gradient as a direct measure of specific angular momentum, these authors inferred a launch radius of 0.05 +0.05 −0.02 au, which suggested that the SiO jet arises from the inner disk edge.…”

Interaction between a pulsating jet and a surrounding disk wind

“…Detailed models are successful at reproducing the higher molecule richness of Class 0 jets (Panoglou et al 2012) the broad water line components revealed by Herschel/HIFI (Yvart et al 2016), and the rotation signatures recently resolved by ALMA in the HH212 jet and in the slow wider angle wind surrounding it (Lee et al 2017;Tabone et al 2017). However, the same disk wind models predict that the fastest, SiO-rich streamlines in HH212 (flowing at ∼ 100 km s −1 ) would be launched from 0.05-0.2 au, within the dust sublimation radius (Tabone et al 2017).…”

“…Yet, jets from the youngest protostars -so-called Class 0 -are much brighter in molecules (e.g., Tafalla et al 2000) than jets from more evolved protostars and pre-main sequence stars which are mainly atomic; Molecules have been traced as close as 20-100 au from the source (e.g., Lee et al 2017;Hodapp & Chini 2014). The origin of this selective molecular richness remains an important issue for models of the jet origin.…”