HERBIG-HARO OBJECTS IN THE \\RHO OPHIUCHI CLOUD

Abstract

ABSTRACT Using deep, narrow-band images of the main ρ Oph dark cloud centered on the wavelengths of Hα and [S~II], we present evidence for three new Herbig-Haro objects. This increases the total number in the cloud to five. In addition, positions for 5 candidate Herbig-Haro objects are given. Relatively high [S~II]/Hα ratios indicate low excitation conditions for all of these nebulae. We list potential exciting stars for each Herbig-Haro object and candidate by identifying nearby young stellar objects with strong infrared excesses and/or millimeter continuum emission. The location of most of these nebulae near the cloud edges underscores the important role that extinction by dust plays in the ρ Oph cloud in masking the presence of Herbig-Haro objects. Among the newly identified Herbig-Haro objects is a jet-like string of emission nebulae emanating from the classical T Tauri star SR~4. [S~II] emission is also found coincident with a knot of strong molecular hydrogen emission associated with the highly-collimated VLA~1623 molecular outflow. Indeed, the low excitation nature of all of the objects in our study, coupled with the high extinction of the cloud, suggests that a deep survey for shocked molecular hydrogen at λ=2.122 μm would be the best way to search for evidence of strong winds from the large population of young stellar objects in the cloud.