EMBEDDED PROTOSTARS IN THE DUST, ICE, AND GAS IN TIME (DIGIT)<i>HERSCHEL</i>KEY PROGRAM: CONTINUUM SEDs, AND AN INVENTORY OF CHARACTERISTIC FAR-INFRARED LINES FROM PACS SPECTROSCOPY

Abstract

&lt;p&gt;\n\tWe present 50-210 {$μ$}m spectral scans of 30 Class 0/I protostellar sources, obtained with Herschel-PACS, and 0.5-1000 {$μ$}m spectral energy distributions, as part of the Dust, Ice, and Gas in Time Key Program. Some sources exhibit up to 75 H$_{2}$O lines ranging in excitation energy from 100 to 2000 K, 12 transitions of OH, and CO rotational lines ranging from J = 14 {\narr} 13 up to J = 40 {\narr} 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 {$μ$}m [O I] flux ratio is 17.2 {plusmn} 9.2. The [O I] 63 {$μ$}m 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 (${$$ackslash$langle ${$ ${$N$}$$}$$ackslash$rangle$}$ = (0.70 +/- 1.12)${$${$$}$ $ackslash$times 10^{}${$49$}$$}$ total particles). ${$ ${$N$}$$}$_CO correlates strongly with L $_{bol}$, but neither T $_{rot}$ nor ${$ ${$N$}$$}$_CO(warm)/${$ ${$N$}$$}$_CO(hot) correlates with L $_{bol}$, suggesting that the total excited gas is related to the current source luminosity, but that the excitation is primarily determined by the physics of the interaction (e.g., UV-heating/shocks). Rotational temperatures for H$_{2}$O (${$$ackslash$langle ${$T_rot$}$$ackslash$rangle $}$ = 194 +/- 85 K) and OH (${$$ackslash$langle ${$T_rot$}$$ackslash$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.&lt;/p&gt;