James Webb Space Telescope Feed Post

PROJECT-J: JWST observations of HH46~IRS and its outflow. Overview and first results

(a): NIRSpec images of line+continuum emission at 1.87 and 2.12 µm (left) are compared with archival NIRCam images in the F187N and F200W filters (right). The NIRCam images (spatial resolution 31 mas/pixel) reveal a secondary source (B) located at about 0.''23 from the primary (A), i.e. about the position where Reipurth et al. (2000) reported the detection of a companion. The arrows indicate the direction of the jet axis driven by source A, and the H2 A1 arc-shaped knot apparently pointing towards source B. (b): Comparison of a HST image in the F205W filter of the HH46 IRS binary taken in 1998 with the NIRCam F200W image taken in 2023. Blue circles in both images indicate the position of the sources A and B in the HST image. Source B appears to have rotated around source A by about 13° counterclockwise. Abstract: We present the first results of the JWST program PROJECT-J (PROtostellar JEts Cradle Tested with JWST ), designed to study the Class I source HH46 IRS and its outflow through NIRSpec and MIRI spectroscopy (1.66 to 28 micron). The data provide line-images (~ 6.6" in length with NIRSpec, and up to 20" with MIRI) revealing unprecedented details within the jet, the molecular outflow and the cavity. We detect, for the first time, the red-shifted jet within ~ 90 au from the source. Dozens of shock-excited forbidden lines are observed, including highly ionized species such as [Ne III] 15.5 micron, suggesting that the gas is excited by high velocity (> 80 km/s) shocks in a relatively high density medium. Images of H2 lines at different excitations outline a complex molecular flow, where a bright cavity, molecular shells, and a jet-driven bow-shock interact with and are shaped by the ambient conditions. Additional NIRCam 2 micron images resolve the HH46 IRS ~ 110 au binary system and suggest that the large asymmetries observed between the jet and the H2 wide angle emission could be due to two separate outflows being driven by the two sources. The spectra of the unresolved binary show deep ice bands and plenty of gaseous lines in absorption, likely originating in a cold envelope or disk. In conclusion, JWST has unraveled for the first time the origin of the HH46 IRS complex outflow demonstrating its capability to investigate embedded regions around young stars, which remain elusive even at near-IR wavelengths.