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Session 21 - Jets, H-H Objects, and Molecular Outflows.
Display session, Monday, January 15
North Banquet Hall, Convention Center
\def \HaH\alpha \def \mum\mum
We present near infrared images of the Herbig-Haro 110 jet centered at the molecular hydrogen lines v = 1-0 2.121 \mum and v = 2-1 2.248 \mum. In YSOs these lines are mostly excited by low velocity shocks and the energy released by turbulent processes. The ratio of these of lines provides us with a preliminary diagnostic of the molecular gas excitation. The HH 110 jet was selected for four reasons: (i) it has a complicated optical `turbulent' morphology, (ii) it is close to a high density circumstellar environment (a molecular core), (iii) this object does not have an obvious driving source, and (iv) theoretical models suggest that this object corresponds to the early stages of a jet-cloud collision.
We find that the molecular hydrogen emission follows the optical \Ha and [SII] emission in a `straight' section of the jet (the northern \sim 1^'), but it becomes shifted westward and separated from the optical emission afterwards. We suggest that these morphological properties of the molecular hydrogen emission are consistent with that of a boundary layer.
The 2.248 \mum emission is faint in most condensations, except for the B1, E1, H1 and P1 knots, where it is clearly detected. The ratio of the 2.121 \mum to the 2.248 \mum lines for these knots ranges from 4.5 to 7.5 which implies excitation temperatures of \sim 2400 - 3100 K. The brightest condensation, H1, however, has a smaller ratio (\sim 1.9) and a higher temperature (\sim 5900 K), which suggests a non-isothermal jet structure. In those cases where the H_2 emission is likely to be due to shocks, the line ratios are small enough to be explained by either C or J-type shocks.
