Optical spectroscopy of known and suspected Herbig-Haro objects

Optical spectra of a number of suspected Herbig-Haro objects are presented. From these, the nature of these nebulosities are determined. Several of the nebulae are of very high density, perhaps due to their extreme youth. Extinctions measured toward DG Tau HH and the L1551 IRS 5 optical jet are in each case substantially less than the stellar values. It is suggested that this phenomenon reflects the existence of appreciably thick circumstellar dust disks around these, and two additional, exciting stars. Shock model diagnostics suggest that the emission lines in these Herbig-Haro nebulae arise in modest velocity shocks with sizable preshock densities in several cases. Radial velocities enable lower limits to be placed on the mass loss rates of those stars that have been detected in the radio continuum.