Astrophys. J., Suppl. Ser., 235, 30-30 (2018/April-0)
The Herschel-PACS legacy of low-mass protostars: the properties of warm and hot gas components and their origin in far-UV illuminated Shocks.
KARSKA A., KAUFMAN M.J., KRISTENSEN L.E., VAN DISHOECK E.F., HERCZEG G.J., MOTTRAM J.C., TYCHONIEC L., LINDBERG J.E., EVANS II N.J., GREEN J.D., YANG Y.-L., GUSDORF A., ITRICH D. and SIODMIAK N.
Abstract (from CDS):
Recent observations from Herschel allow the identification of important mechanisms responsible both for the heating of the gas that surrounds low-mass protostars and for its subsequent cooling in the far-infrared. Shocks are routinely invoked to reproduce some properties of the far-IR spectra, but standard models fail to reproduce the emission from key molecules, e.g., H2O. Here, we present the Herschel Photodetector Array Camera and Spectrometer (PACS) far-IR spectroscopy of 90 embedded low-mass protostars (Class 0/I). The Herschel-PACS spectral maps, covering ∼55-210 µm with a field of view of ∼50'', are used to quantify the gas excitation conditions and spatial extent using rotational transitions of H2O, high-J CO, and OH, as well as [O I] and [C II]. We confirm that a warm (∼300 K) CO reservoir is ubiquitous and that a hotter component (760 ± 170 K) is frequently detected around protostars. The line emission is extended beyond ∼1000 au spatial scales in 40/90 objects, typically in molecular tracers in Class 0 and atomic tracers in Class I objects. High-velocity emission (>=90 km s–1) is detected in only 10 sources in the [O I] line, suggesting that the bulk of [O I] arises from gas that is moving slower than typical jets. Line flux ratios show an excellent agreement with models of C-shocks illuminated by ultraviolet (UV) photons for pre-shock densities of ∼105 cm–3 and UV fields 0.1-10 times the interstellar value. The far-IR molecular and atomic lines are a unique diagnostic of feedback from UV emission and shocks in envelopes of deeply embedded protostars.
© 2018. The American Astronomical Society. All rights reserved.
infrared: ISM - ISM: jets and outflows - ISM: molecules
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