We present 50-210 µm spectral scans of 30 Class 0/I protostellar sources , obtained with Herschel -PACS , and 0.5-1000 µm SEDs , as part of the Dust , Ice , and Gas in Time ( DIGIT ) Key Program .
Some sources exhibit up to 75 H _ { 2 } O lines ranging in excitation energy from 100-2000 K , 12 transitions of OH , and CO rotational lines ranging from J = 14 \rightarrow 13 up to J = 40 \rightarrow 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 µm [ O i ] flux ratio is 17.2 \pm 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 ( \mbox { $ \langle \mbox { $ \mathcal { N } $ } \rangle$ } = ( 0.70 \pm 1.12 ) \mbox { $ { } \times 10 ^ { % 49 } $ } total particles ) . \mbox { $ \mathcal { N } $ } _ { CO } correlates strongly with L _ { bol } , but neither T _ { rot } nor \mbox { $ \mathcal { N } $ } _ { CO } ( warm ) / \mbox { $ \mathcal { 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 H _ { 2 } O ( \mbox { $ \langle \mbox { $T _ { rot } $ } \rangle$ } = 194 \pm 85 K ) and OH ( \mbox { $ \langle \mbox { $T _ { rot } $ } \rangle$ } = 183 \pm 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 .