Collimated Jet and outflow from the Low-luminosity Protostar IRAS 16253‑2429 in a Quiescent Accretion Phase with ALMA and JWST

ABSTRACT :
We present 2.9-28 micron JWST observations of the Class 0 protostar IRAS 16253-2429, the lowest luminosity (Lbol=0.2 LSun)/mass (0.2 MSun) source in the Cycle 1 JWST program Investigating Protostellar Accretion, augmented by observations from the ALMA eDisk program. We find a collimated jet in shock-heated ionic/atomic lines surrounded by a wide cavity traced in scattered light. The atomic jet has a velocity of ~170 km/s with a width ranging from 23-60 au. The jet is surrounded by lower-velocity, structured, warm H2 emission that extends to the cavity wall traced by CO with ALMA; converging to a width similar to the dust disk diameter at the cavitie’s apex. These suggest that H2 is tracing a wide-angle wind that accelerates infalling gas, producing the entrained gas outflow mapped by ALMA. By comparing the flux ratios of fine structure line emission in the jet to shock models, we derive shock speed ~50 km/s, preshock density ~2000/cc, and compute a mass loss rate <=1.1 x 10^−10 MSun/yr. A lack of H2O emission from the protostar indicates that UV photons are destroying H2O to produce the observed OH emission. Given that the only likely source of UV photons is accretion shock, the OH emission implies a low accretion rate of 2.4 x 10^−9 MSun/yr. These data indicate that I16253 is in a quiescent period between episodes of active accretion, providing an increasingly rich picture of how accretion and accretion-driven outflow shape the masses of stars/low mass IMF.