Herschel observations of EXtra-Ordinary Sources (HEXOS) : Methanol as a probe of physical conditions in Orion KL

S. Wang (1) , E.A. Bergin (1) , N.R. Crockett (1) , P.F. Goldsmith (2) , Dc. Lis (3) , J.C. Pearson (2) , P. Schilke (4, 5) , Ta. Bell (3) , C. Comito (4) , Ga. Blake (6) , E. Caux (7) , C. Ceccarelli (8) , J. Cernicharo (9) , F. Daniel (10, 9) , Ml. Dubernet (11, 12) , M. Emprechtinger (3) , P. Encrenaz (10) , M. Gerin (10) , T.F. Giesen (5) , J.R. Goicoechea (9) , H. C. Gupta (2) , E. Herbst (13) , C. Joblin (7) , D. Johnstone (14) , W.D. Langer (2) , W.B. Latter (15) , S.D. Lord (15) , S. Maret (8) , P.G. Martin (16) , G. J. Melnick (17) , K. M. Menten (18) , P. Morris (15) , H. S. P. Müller (5) , J.A. Murphy (19) , D.A. Neufeld (20) , V. Ossenkopf (12, 21) , M. Perault (10) , T. G. Phillips (3) , R. Plume (22) , S.-L. Qin (5) , S. Schlemmer (5) , J. Stutzki (5) , N. Trappe (19) , F.F.S van Der Tak (21) , C. Vastel (7) , H.W. Yorke (2) , S. Yu (2) , J. Zmuidzinas (3)

1 Department of Astronomy [Ann Arbor]
2 JPL - Jet Propulsion Laboratory
3 Cahill Center for Astronomy and Astrophysics
4 Max Planck Institute for Radio Astronomy
5 I. Physikalisches Institut [Köln]
6 Division of Geological and Planetary Sciences [Pasadena]
7 CESR - Centre d'étude spatiale des rayonnements
8 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
9 CAB - Centro de Astrobiologia [Madrid]
10 LERMA - Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique
11 LPMAA - Laboratoire de Physique Moleculaire pour l'Atmosphere et l'Astrophysique
12 LUTH (UMR_8102) - Laboratoire Univers et Théories
13 Department of Physics and Astronomy [Columbus]
14 NRC Herzberg Institute of Astrophysics
15 IPAC - Infrared Processing and Analysis Center
16 CITA - Canadian Institute for Theoretical Astrophysics
17 CfA - Harvard-Smithsonian Center for Astrophysics
18 MPIFR - Max-Planck-Institut für Radioastronomie
19 Maynooth University - National University of Ireland Maynooth
20 Department of Physics and Astronomy [Baltimore]
21 SRON - SRON Netherlands Institute for Space Research
22 Department of Physics and Astronomy [Calgary]

We have examined methanol emission from Orion KL with the Herschel/HIFI instrument, and detected two methanol bands centered at 524 GHz and 1061 GHz. The 524 GHz methanol band (observed in HIFI band 1a) is dominated by the isolated Delta J = 0, K = -4 -> -3, v(t) = 0 Q branch, and includes 25 E-type and 2 A-type transitions. The 1061 GHz methanol band (observed in HIFI band 4b) is dominated by the Delta J = 0, K = 7 -> 6, v(t) = 0 Q branch transitions which are mostly blended. We have used the isolated E-type vt = 0 methanol transitions to explore the physical conditions in the molecular gas. With HIFI's high velocity resolution, the methanol emission contributed by different spatial components along the line of sight toward Orion KL (hot core, low velocity flow, and compact ridge) can be distinguished and studied separately. The isolated transitions detected in these bands cover a broad energy range (upper state energy ranging from 80 K to 900 K), which provides a unique probe of the thermal structure in each spatial component. The observations further show that the compact ridge is externally heated. These observations demonstrate the power of methanol lines as probes of the physical conditions in warm regions in close proximity to young stars.

Domaines: Planétologie et astrophysique de la terre [astro-ph.EP]; Planétologie et astrophysique de la terre [astro-ph.EP]

S. Wang, E.A. Bergin, N.R. Crockett, P.F. Goldsmith, Dc. Lis, et al.. Herschel observations of EXtra-Ordinary Sources (HEXOS) : Methanol as a probe of physical conditions in Orion KL. Astronomy and Astrophysics - A&A, 2011, 527, pp.A95. ⟨10.1051/0004-6361/201015079⟩. ⟨hal-00601295⟩