Embedded Protostars in the Dust, Ice, and Gas In Time (DIGIT) Herschel Key Program: Continuum SEDs, and an Inventory of Characteristic Far-infrared Lines from PACS Spectroscopy
Abstract
We present 50-210 μm spectral scans of 30 Class 0/I protostellar sources, obtained with Herschel-PACS, and 0.5-1000 μm spectral energy distributions, as part of the Dust, Ice, and Gas in Time Key Program. Some sources exhibit up to 75 H2O lines ranging in excitation energy from 100 to 2000 K, 12 transitions of OH, and CO rotational lines ranging from J = 14 → 13 up to J = 40 → 39. [O I] is detected in all but one source in the entire sample; among the sources with detectable [O I] are two very low luminosity objects. The mean 63/145 μm [O I] flux ratio is 17.2 ± 9.2. The [O I] 63 μm line correlates with L bol, but not with the time-averaged outflow rate derived from low-J CO maps. [C II] emission is in general not local to the source. The sample L bol increased by 1.25 (1.06) and T bol decreased to 0.96 (0.96) of mean (median) values with the inclusion of the Herschel data. Most CO rotational diagrams are characterized by two optically thin components ({\langle { {N}}\rangle} = (0.70 +/- 1.12){{} \times 10^{49}} total particles). { {N}}_CO correlates strongly with L bol, but neither T rot nor { {N}}_CO(warm)/{ {N}}_CO(hot) correlates with L bol, suggesting that the total excited gas is related to the current source luminosity, but that the excitation is primarily determined by the physics of the interaction (e.g., UV-heating/shocks). Rotational temperatures for H2O ({\langle {T_rot}\rangle } = 194 +/- 85 K) and OH ({\langle {T_rot}\rangle } =183 +/- 117 K) are generally lower than for CO, and much of the scatter in the observations about the best fit is attributed to differences in excitation conditions and optical depths among the detected lines.
Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.- Publication:
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The Astrophysical Journal
- Pub Date:
- June 2013
- DOI:
- 10.1088/0004-637X/770/2/123
- arXiv:
- arXiv:1304.7389
- Bibcode:
- 2013ApJ...770..123G
- Keywords:
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- circumstellar matter;
- stars: formation;
- stars: pre-main sequence;
- stars: winds;
- outflows;
- submillimeter: stars;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 58 pages, 37 figures