Collisionally Excited Filaments in Hubble Space Telescope Hα and Hβ Images of HH 1/2
Bally, J.; Raga, A. C.; Reipurth, B.; Castellanos-Ramírez, A.; Chiang, Hsin-Fang
Mexico, United States
Abstract
We present new Hα and Hβ images of the HH 1/2 system, and we find that the Hα/Hβ ratio has high values in ridges along the leading edges of the HH 1 bow shock and of the brighter condensations of HH 2. These ridges have Hα/Hβ = 4 → 6, which is consistent with collisional excitation from the n = 1 to the n = 3 and 4 levels of hydrogen in a gas of temperatures T = 1.5 → 10 × 104 K. This is therefore the first direct evidence that the collisional excitation/ionization region of hydrogen just behind Herbig-Haro shock fronts is detected.