NEAR-INFRARED IMAGING OF THE JETS AND FLOWS ASSOCIATED WITH HERBIG-HARO OBJECTS HH-91, HH-110, AND HH-111

We present near-infrared imaging of the jets and outflows associated with the Herbig-Haro objects HH 91, HH 110 and HH 111. We compare our narrowband H-2 v = 1-0 S(1) (2.121 mu m) and broadband K images with optical [S II] and H alpha images of the same regions. We find that many of the brightest knots in [S II] and H alpha have counterparts in H-2, although there are some marked differences in morphology. In HH 91 the H-2 emission is highly clumpy, like the [S II] emission, although the H-2 is mostly confined to the low-excitation regions of the flow. H-2 emission also coincides with and outlines the northern edge of a filamentary, optical, ''jetlike'' feature in HH 91. We interpret this as possible evidence for entrainment of ambient gas along the northern boundary of this flow. More striking differences between the H-2 and optical data are seen in the HH 110 outflow. The ''wiggling'' H alpha jet appears much straighter in H-2. We suggest that close to the source the H-2 traces a laminar, mostly molecular jet, while the H alpha traces a more extensive turbulent ''mixing layer'' that separates the jet from the ambient medium. Also, near HH 110 we have found a second and probably third collimated H alpha jet. Neither jet is visible in optical images of the region. Finally, in HH 111 we see the brightest optical features also in H-2, including the bow shock at the westerly head of the jet, knot V. Along the jet, the H-2 peaks coincide closely with the [S II] knots (after taking into account proper motions), although in knot V the H-2 is shifted upstream of the [S II] peak by similar to 1'' (400 AU): the H-2 therefore probably derives from the bow shock wings in knot V.