Evolutionary Sequence in High Mass Pre-Stellar Cores
F.F.S. van der Tak, W. Frieswijk
Two high-mass molecular clouds (identified as infrared dark clouds) were observed with HIFI on the Herschel Observatory in the 557 H2O and N2H+ lines. In each cloud, two cores were identified for the study with HIFI: a sub-mm continuum peak and an ammonia peak. We also have C17O (3−2) and methanol observations toward the cores. The cores contain 200 to 2800 solar masses of material and some of the cores are arguably already engaged in active star formation. The four observations show a broad range of water emission and absorption profiles. Together with ground based observations we seek to calibrate the "evolutionary" state of the cores. Three of the cores show broad water (15−30 km s−1) line emission. We interpret this emission as evidence of out-flows. One position, however, shows no sign of broad line emission. We suggest that this core is truly "pre-stellar".