Velocity-Resolved [C ll] Emission And [C ll]/Fir Mapping Along Orion With Herschel

Javier R. Goicoechea (1) , D. Teyssier , M. Etxaluze , P. F. Goldsmith (2) , V. Ossenkopf , M. Gerin (1) , E. A. Bergin (3) , J. H. Black (4) , J. Cernicharo (5) , S. Cuadrado , P. Encrenaz (1) , E. Falgarone (1) , A. Fuente (6) , A. Hacar , D. C. Lis (7, 1) , N. Marcelino (8) , G. J. Melnick (9) , H. S. P. Muller (10) , C. Persson (11) , Jérôme Pety (12) , M. Röllig (13) , P. Schilke (14) , R. Simon , R. L. Snell , J. Stutzki (10)

1 LERMA - Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique
2 JPL - Jet Propulsion Laboratory
3 Department of Astronomy [Ann Arbor]
4 OSO - Onsala Space Observatory
5 CAB - Centro de Astrobiologia [Madrid]
6 Observatorio Astronomico Nacional, Madrid
7 CALTECH - California Institute of Technology
8 OABO - INAF - Osservatorio Astronomico di Bologna
9 CfA - Harvard-Smithsonian Center for Astrophysics
10 I. Physikalisches Institut [Köln]
11 OSO - Onsala Space Observatory
12 IRAM - Institut de RadioAstronomie Millimétrique
13 Physikalisches Institut [Köln]
14 MPIFR - Max-Planck-Institut für Radioastronomie

We present the first ~7.‧5 × 11.‧5 velocity-resolved (~0.2 km s$^{-1}$) map of the [C ii] 158 μm line toward the Orion molecular cloud 1 (OMC 1) taken with the Herschel/HIFI instrument. In combination with far-IR (FIR) photometric images and velocity-resolved maps of the H41α hydrogen recombination and CO J = 2-1 lines, this data set provides an unprecedented view of the intricate small-scale kinematics of the ionized/photodissociation region (PDR)/molecular gas interfaces and of the radiative feedback from massive stars. The main contribution to the [C ii] luminosity (~85%) is from the extended, FUV-illuminated face of the cloud (G$_{0}$ > 500, n$_{H}$ > 5 x 10$^5$ cm$^{-3}$) and from dense PDRs (G$_{0}$ ≳ 104, n$_{H}$ ≳ 105 cm-3) at the interface between OMC 1 and the H ii region surrounding the Trapezium cluster. Around ~15% of the [C ii] emission arises from a different gas component without a CO counterpart. The [C ii] excitation, PDR gas turbulence, line opacity (from [13C ii]), and role of the geometry of the illuminating stars with respect to the cloud are investigated. We construct maps of the L[C ii]/{L}{FIR} and {L}{FIR}/{M}{Gas} ratios and show that L[C ii]/{L}{FIR} decreases from the extended cloud component (~10$^{-2}$-10$^{-3}$) to the more opaque star-forming cores (~10$^{-3}$-10$^{-4}$). The lowest values are reminiscent of the “[C ii] deficit” seen in local ultraluminous IR galaxies hosting vigorous star formation. Spatial correlation analysis shows that the decreasing L[C ii]/{L}{FIR} ratio correlates better with the column density of dust through the molecular cloud than with {L}{FIR}/{M}{Gas}. We conclude that the [C ii]-emitting column relative to the total dust column along each line of sight is responsible for the observed L[C ii]/{L}{FIR} variations through the cloud. Uses observations obtained with the IRAM 30 m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).

Mots clés: infrared: galaxies; ISM: clouds; galaxies: ISM; H ii regions

Domaines: Astrophysique galactique [astro-ph.GA]

Javier R. Goicoechea, D. Teyssier, M. Etxaluze, P. F. Goldsmith, V. Ossenkopf, et al.. Velocity-Resolved [C ll] Emission And [C ll]/Fir Mapping Along Orion With Herschel. The Astrophysical Journal, 2015, 812 (1), pp.75. ⟨10.1088/0004-637X/812/1/75⟩. ⟨hal-02493844⟩