Other
Scientific paper
May 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011iaus..280p.329g&link_type=abstract
The Molecular Universe, Posters from the proceedings of the 280th Symposium of the International Astronomical Union held in Tole
Other
Scientific paper
Spitzer-IRS maps of H_2 pure rotational lines from S(0) to S(7) in three outflows from Class 0 sources, namely L1448, BHR71, and NGC2071, are presented. These lines are used, in conjunction with available rovibrational, near-infrared H_2 lines, to probe the physical conditions of the warm gas between hundreds and thousands of Kelvin. We have constructed maps of the molecular hydrogen column density, ortho-to-para ratio and volume density, together with the index of the power law describing the distribution of gas temperature. In all three outflows, the present ortho-to-para ratio significantly deviates from the high temperature equilibrium of 3, being on average between 2.0 and 2.3. These low values, that in general reflect the young age of these flows, are found also in regions of relatively high temperature (around 1000 K), likely indicating that shocks are occurring in a time shorter than that needed for a complete para to ortho conversion. Density maps indicate upper limits close to LTE conditions, i.e. between 10^6-10^7 cm-3; moreover we demonstrate, on the basis of the detections of HD emission spots (R(3) and R(4) lines) that a density stratification does exist, with the low density components (10^4-10^5 cm-3) associated to the coldest gas. The index is found in all flows to be above 3.8: this value is consistent with predictions of multiple C-type bow shocks where the velocity at the apex is sufficient to partially dissociate H_2. The contribution of H_2 to the total cooling is quantitatively similar to that of other abundant molecules emitting in the far-infrared, such as water and CO; moreover, the luminosity radiated away is comparable with the estimated kinetic energy of the swept-out outflow: this supports the scenario in which the shock from which H_2 is emitted is also capable of accelerating the molecular outflow driven at the shock working surface.
Antoniucci Simone
Giannini Teresa
Gusdorf Antoine
Neufeld David
Nisini Brunella
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