Low-excitation Herbig-Haro objects and interstellar extinction

Previous work on low-excitation Herbig-Haro (HH) objects has confirmed the existence of a strongly-enhanced hydrogen two-photon continuum which is produced by low-velocity shocks in neutral material. The theoretical two-photon energy distribution was compared with that observed for HH 43. With the addition of optical (3300 lambda 7000A) data to the ultraviolet (1200 lambda 3100A) data obtained with the I.U.E, the wavelength dependence of interstellar extinction toward HH 43 has been determined.