Detection of Synchrotron Emission from a Unique Herbig Haro Object in Orion

We have obtained radio continuum observations of an HH object, known as the “streamer” in Orion using the VLA in a number of configurations at λ2, 6 and 20cm. This object is located several arc-minutes to the north of HH34 in L1641 cloud and exhibits a remarkably long and narrow structure with dimensions of 5′ × 10′ in optical photographs unlike the morphology of any other HH object. Based on radio continuum observations, we have detected a significant linearly polarized emission at λ6cm from the core of the streamer indicating highly uniform magnetic field geometry. This unusual result suggests that the source responsible for producing the nebulosity is a nonthermal-emitting radio source. Because of the presence of a number of newly born low-mass stars in L1641 and because of the detection of a highly reddened 2μm source coincident with the synchrotron source, it is likely that the source at the core of the streamer is a low-mass star responsible for the non-thermal emission and the HH nebulosity. Presence of synchrotron emission associated with a newly born star supports further view that the magnetic field plays a strong role in the early phase of star formation.

H2 2.12 μm Spectroscopy and Imaging of HH Objects

We have obtained high spectral resolution observations of a number of Herbig-Haro (HH) objects in the H2 v=1-0 S(1) line at 2.12μm. Objects observed included HH1/2, HH7-11, HH19, HH32A, HH40, and HH43, all associated with jet-like features or collimated optical outflows. Here we present velocity-resolved 2.12μm spectroscopy for HH40 (an HH-objects moving close to the line of sight) an for HH43B (an HH-object moving close to the plane of the sky). The full set of observations including interpretation is given in Zinnecker et al. (1989). We also present high spatial resolution H2 2.12μm images of HH40 and HH43. The 2.12μm H2 line profiles were obtained with the UKIRT infrared Fabry-Perot system (effective resolution 30-35 km/s) using a diaphragm of diameter 11” for both HH40 and HH43. The H2 images were obtained with the IR-array imager at the CTIO 1.5m telescope through a narrowband filter centred on the v=1-0 S(1) line. The IR-camera used had 58x62 pixels and a resolution of 0.9”/pixel. The exposure time was 2x120sec and 5x60sec for HH40 and HH43, respectively. The images are sky subtracted, but not fiat fielded, and should be viewed as preliminary test images.

HH 34: The bow shock of a jet

Deep CCD imaging of HH 34 in H∝ shows that the HH-object has a bow shock-like structure, of which the wings can be traced over about 1 arcmin ( pc). A knotty jet is pointing towards the apex of the bow shock structure. Long-slit spectroscopy reveals that 1) the jet has approximately a constant radial velocity and electron density. 2). The spectrum of the jet is of a much lower excitation than that of HH 34. 3) HH 34 has a complex velocity and line excitation structure. The extended bow shock is interpreted by a jet of which the working surface is propagating with high velocity (≈ 200 km/s) through a partially ionized medium.