Near-infrared spectroscopy of photodissociation regions: the Orion bar and Orion S

摘要

We have obtained moderate-resolution (R～3000) spectra of the Orion bar Orion S regions at J (1.25 μm), H (1.64 μm), and K(2.2 μm). Toward the bar, the observations reveal a large number of H_2 emission lines that, when compared to model predictions of Draine & Bertoldi, are indicative of a High-density photodissociation region(PDR) (n_H = 110~6 cm~3, χ= 10~5, T_0 = 1000 K) rather than of Shocked material. Behind the bar and into the molecular cloud, the H_2 spectrum again matches well With that predicted for a dense PDR(n_H = 10~6 cm~-3) but with a lower temperature (T_o = 5000 K) and UV field strength (χ= 10~4).