PT Journal
AU Mookerjea, B
   Giesen, T
   Stutzki, J
   Cernicharo, J
   Goicoechea, JR
   De Luca, M
   Bell, TA
   Gupta, H
   Gerin, M
   Persson, CM
   Sonnentrucker, P
   Makai, Z
   Black, J
   Boulanger, F
   Coutens, A
   Dartois, E
   Encrenaz, P
   Falgarone, E
   Geballe, T
   Godard, B
   Goldsmith, PF
   Gry, C
   Hennebelle, P
   Herbst, E
   Hily-Blant, P
   Joblin, C
   Ka<c5><ba>mierczak, M
   Kołos, R
   Krełowski, J
   Lis, DC
   Martin-Pintado, J
   Menten, KM
   Monje, R
   Pearson, JC
   Perault, M
   Phillips, TG
   Plume, R
   Salez, M
   Schlemmer, S
   Schmidt, M
   Teyssier, D
   Vastel, C
   Yu, S
   Dieleman, P
   Güsten, R
   Honingh, CE
   Morris, P
   Roelfsema, P
   Schieder, R
   Tielens, AGGM
   Zmuidzinas, J
TI Excitation and abundance of C3 in star forming cores. Herschel/HIFI observations of the sight-lines to W31C and W49N
SO Astron. Astrophys.
PY 2010
BP L13
VL 521
DI 10.1051/0004-6361/201015095
DE HEB mixer applications; HIFI; Herschel; ISM: lines and bands / ISM: molecules / radiative transfer / ISM: individual objects: W49N / ISM: individual objects: W31C
AB We present spectrally resolved observations of triatomic carbon (C3) in several ro-vibrational transitions between the vibrational ground state and the low-energy ν2 bending mode at frequencies between 1654–1897 GHz along the sight-lines to the submillimeter continuum sources W31C and W49N, using Herschel's HIFI instrument. We detect C3 in absorption arising from the warm envelope surrounding the hot core, as indicated by the velocity peak position and shape of the line profile. The sensitivity does not allow to detect C3 absorption due to diffuse foreground clouds. From the column densities of the rotational levels in the vibrational ground state probed by the absorption we derive a rotation temperature (Trot) of ~50-70 K, which is a good measure of the kinetic temperature of the absorbing gas, as radiative transitions within the vibrational ground state are forbidden. It is also in good agreement with the dust temperatures for W31C and W49N. Applying the partition function correction based on the derived Trot, we get column densities N(C3) ~ 7–9 × 1014 cm-2 and abundance x(C3) ~ 10-8 with respect to H2. For W31C, using a radiative transfer model including far-infrared pumping by the dust continuum and a temperature gradient within the source along the line of sight we find that a model with x(C3) = 10-8, Tkin = 30–50 K, N(C3) = 1.5 × 1015 cm-2 fits the observations reasonably well and provides parameters in very good agreement with the simple excitation analysis.
ER