continuum SEDs, and an inventory of characteristic far-infrared lines from PACs spectroscopy
We present 50-210 um spectral scans of 30 Class 0/I protostellar sources, obtained with Herschel-PACS, and 0.5-1000 um SEDs, as part of the Dust, Ice, and Gas in Time (DIGIT) Key Program. Some sources exhibit up to 75 H2O lines ranging in excitation energy from 100-2000 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 (VeLLOs). The mean 63/145 um [O I] flux ratio is 17.2 +/- 9.2. The [O I] 63 um line correlates with Lbol, 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 Lbol increased by 1.25 (1.06) and Tbol 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 ( = (0.70 +/- 1.12) x 10^49 total particles). N_CO correlates strongly with Lbol, but neither Trot nor N_CO(warm)/N_CO(hot) correlates with Lbol, 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 ( = 194 +/- 85 K) and OH ( = 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 amongst the detected lines.