HH 666: The Axis of Evil in the Carina Nebula

Abstract

We report the discovery of the iniquitous parsec-scale outflow HH 666—the first protostellar jet in the Carina Nebula—as well as the infrared identification of its embedded driving source. The HH 666 jet emanates from a bright-rimmed molecular globule (G287.57-0.91) at the head of a dust pillar in the southern part of Carina. Optical and near-infrared images reveal structures that resemble bow shocks and internal working surfaces in other Herbig-Haro (HH) jets, and which are especially bright in [Fe II] λ16435. Except for extended bow shock wings, all features lie within a few degrees of a single axis oriented roughly southeast to northwest, with a remarkable highly collimated flow breaking out of the natal globule. Long-slit echelle spectra reveal only redshifted velocities toward the southeast of the globule and blueshifted velocities toward the northwest. The observed features conspire to form a single, coherent bipolar jet with a total projected length of over 45, or more than 3 pc. Doppler shifts as high as ±250 km s-1 are seen, indicating that the jet axis has a significant tilt from the plane of the sky, and the total length of the jet may be closer to 4 or 5 pc. HH 666 is therefore among the longest HH jets known. Condemned to toil in the inferno of the Carina Nebula, scorched by UV radiation from the hot stars that power the H II region, much of the jet is influenced by radiative excitation. Infrared images reveal a reddened star embedded in the molecular globule lying along the jet axis. We identify this evildoer (HH 666 IRS) as the likely driving source of the jet. The infrared spectral energy distribution of HH 666 IRS is consistent with that of a Class I protostellar object, with a luminosity of a few hundred to 103 L⊙, and a probable main-sequence mass of a few to 8 M⊙. This Class I object associated with a prominent bipolar jet constitutes the first direct evidence of ongoing active star formation by accretion in the Carina Nebula.