NEAR-INFRARED EMISSION-LINE IMAGES OF 3 HERBIG-HARO OBJECTS

HH 7-11, HH 12, and HH 34 have been observed with an infrared array camera using nine narrow-band filters. We report the first detection of the 1.64-mu-m line of [Fe II] in all three Herbig-Haro objects, including the HH 34 jet. Vibrational lines of H-2 were imaged in HH 7-11 and HH 12, but were not detected in HH 34. Brackett-gamma emission was not detected in any of the HH objects. The infrared results are compared with optical [S II] images. No new emission-line regions are revealed in the infrared data, suggesting that extinction plays little role in determining the optical appearance of these HH objects. The spatial distribution of [Fe II] emission is generally similar to the distribution of 6717 angstrom [S II] emission. The [Fe II]/[S II] ratio is very different in HH 12E, where the value is down by a factor of 7 relative to the rest of HH 12. At this location we suggest that the cooling and recombining flow behind the shock is disrupted before the [Fe II] emission zone can form. In HH 7-11 and HH 12, H-2 emission peaks are nearly always accompanied by [Fe II] and [S II] emission. In three locations (western HH 7; eastern HH 12C and HH 12D) ionized gas peaks occur without H-2 counterparts; these locations all occur 2"-5" upstream of H-2 emission. We identify these peaks without H-2 as shocked jet/wind material, displaced upstream from the H-2 emission at the flow terminus. We suggest that the geometry of a flow obstacle controls whether or not the standoff distance between the molecular and ionized gas shocks is large enough to be observable. No infrared continuum emission was detected from any of the HH objects, indicating that none contain embedded stars. An infrared reflection nebula has been detected to the north of the HH 34 exciting star.