Proper motions of collimated jets from intermediate-mass protostars in the Carina Nebula

Abstract

We present proper motion measurements of 37 jets and HH objects in the Carina Nebula measured in two epochs of H α images obtained ∼10 yr apart with Hubble Space Telescope/Advanced Camera for Surveys (ACS). Transverse velocities in all but one jet are faster than 25 km s −1 , confirming that the jet-like H α features identified in the first epoch images trace outflowing gas. Proper motions constrain the location of the jet-driving source and provide kinematic confirmation of the intermediate-mass protostars that we identify for 20/37 jets. Jet velocities do not correlate with the estimated protostar mass and embedded driving sources do not have slower jets. Instead, transverse velocities (median ∼75 km s −1 ) are similar to those in jets from low-mass stars. Assuming a constant velocity since launch, we compute jet dynamical ages (median ∼10 4 yr). If continuous emission from inner jets traces the duration of the most recent accretion bursts, then these episodes are sustained longer (median ∼700 yr) than the typical decay time of an FU Orionis outburst. These jets can carry appreciable momentum that may be injected into the surrounding environment. The resulting outflow force, dP/dt, lies between that measured in low-and high-mass sources, despite the very different observational tracers used. Smooth scaling of the outflow force argues for a common physical process underlying outflows from protostars of all masses. This latest kinematic result adds to a growing body of evidence that intermediate-mass star formation proceeds like a scaled-up version of the formation of low-mass stars.

High-resolution images of two wiggling stellar jets, MHO 1502 and MHO 2147, obtained with GSAOI+GeMS

“…The knotted structure of several jets, in particular parsecscale jets, has been interpreted as a "fossil record" of outbursts or FU Orionis events (Hartmann & Kenyon 1996) that the exciting sources have undergone in the past (Reipurth 1985(Reipurth , 1989Reipurth et al 1997;Reipurth & Bally 2001;McGroarty & Ray 2004). However, the elapse of time between ejections or knots (∼10 3 yr) is about an order of magnitude less than that of the FU Orionis outbursts (∼10 4 yr), which casts doubt on the FU Orionis status of the knotty-jet exciting sources (Ioannidis & Froebrich 2012;Reiter et al 2015Reiter et al , 2017Froebrich & Makin 2016). The knotted structure of the MHO 1502 jet profile, with pairs of quasi-opposite emissions, suggests that the ejections from the exciting source have been intermittent.…”

Molecular jets from low-mass young protostellar objects

“…The blue and red arrows show the disk rotation star-formation efficiency (Bally 2016). Interestingly, jets are also detected around brown dwarfs (e.g., Whelan et al 2005;Riaz et al 2017), intermediate-mass protostars (e.g., Zapata et al 2010;Reiter et al 2017;Takahashi et al 2019), and highmass protostars (Reipurth and Bally 2001;Zapata et al 2006;Carrasco-González et al 2010;Ellerbroek et al 2013;Caratti o Garatti et al 2015), suggesting that the low-mass star formation scenario may apply to these objects.…”

High-resolution images of two wiggling stellar jets, MHO 1502 and MHO 2147, obtained with GSAOI+GeMS

“…The knotted structure of several jets, in particular parsecscale jets, has been interpreted as a 'fossil record' of outbursts or FU Orionis events (Hartmann & Kenyon 1996) that the exciting sources have undergone in the past (Reipurth 1985(Reipurth , 1989Reipurth et al 1997;Reipurth & Bally 2001;McGroarty & Ray 2004). However, the elapse of time between ejections or knots (∼ 10 3 yr) is about an order of magnitude less than that of the FU Orionis outbursts (∼ 10 4 yr), which casts doubt on the FU Orionis status of the knotty-jet exciting sources (Ioannidis & Froebrich 2012;Reiter et al 2015;Froebrich & Makin 2016;Reiter et al 2017). The knotted structure of the MHO 1502 jet profile, with pairs of quasi-opposite emissions, suggests that the ejections from the exciting source have been intermittent.…”