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Herschel/HIFI observations of spectrally resolved methylidyne signatures toward the high-mass star forming core NGC6334I | | M.H.D. van der Wiel
; F.F.S. van der Tak
; D.C. Lis
; E.A. Bergin
; C. Comito
; M. Emprechtinger
; P. Schilke
; E. Caux
; C. Ceccarelli
; A. Baudry
; P.F. Goldsmith
; E. Herbst
; W. Langer
; S. Lord
; D. Neufeld
; J. Pearson
; T. Philips
; R. Rolffs
; H. Yorke
; A. Bacmann
; M. Benedettini
; G.A. Blake
; A. Boogert
; S. Bottinelli
; S. Cabrit
; P. Caselli
; A. Castets
; J. Cernicharo
; C. Codella
; A. Coutens
; N. Crimier
; K. Demyk
; C. Dominik
; P. Encrenaz
; E. Falgarone
; A. Fuente
; M. Gerin
; F. Helmich
; P. Hennebelle
; T. Henning
; P. Hily-Blant
; T. Jacq
; C. Kahane
; M. Kama
; A. Klotz
; B. Lefloch
; A. Lorenzani
; S. Maret
; G. Melnick
; B. Nisini
; S. Pacheco
; L. Pagani
; B. Parise
; M. Salez
; P. Saraceno
; K. Schuster
; A.G.G.M. Tielens
; C. Vastel
; S. Viti
; V. Wakelam
; A. Walters
; F. Wyrowski
; K. Edwards
; J. Zmuidzinas
; P. Morris
; L.A. Samoska
; D. Teyssier
; | | Date: |
9 Jul 2010 | | Abstract: | In contrast to extensively studied dense star forming cores, little is known
about diffuse gas surrounding star forming regions. We aim to study molecular
gas in the high-mass star forming region NGC6334I, including diffuse, quiescent
components which are inconspicuous in widely used molecular tracers such as CO.
We present Herschel/HIFI observations of CH toward NGC6334I observed as part of
the CHESS Key Program. HIFI resolves the hyperfine components of its J=3/2-1/2
transition, observed in emission as well as in absorption. The CH emission
appears close to the systemic velocity of NGC6334I, while a linewidth of 3 km/s
is smaller than previously observed in dense gas tracers such as NH3 and SiO.
The CH abundance in the hot core is 7 10^-11, two to three orders of magnitude
lower than in diffuse clouds. While other studies find distinct outflows in,
e.g., CO and H2O toward NGC6334I, we do not detect outflow signatures in CH. To
explain the absorption signatures, at least two absorbing components are needed
at -3.0 and +6.5 km/s with N(CH)=7 10^13 and 3 10^13 cm^-2. Two additional
absorbing clouds are found at +8.0 and 0.0 km/s, both with N(CH)=2 10^13 cm^-2.
Turbulent linewidths for the four absorption components vary between 1.5 and
5.0 km/s in FWHM. We constrain physical properties of our CH clouds by matching
our CH absorbers with other absorption signatures. In the hot core, molecules
such as H2O and CO trace gas that is heated and dynamically influenced by
outflow activity, whereas CH traces more quiescent material. The four CH
absorbers have column densities and turbulent properties consistent with
diffuse clouds: two are located near NGC6334, and two are unrelated foreground
clouds. Local density and dynamical effects influence the chemical composition
of physical components of NGC6334, causing some components to be seen in CH but
not in other tracers, and vice versa. | | Source: | arXiv, 1007.1539 | | Services: | Forum | Review | PDF | Favorites | |
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