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J.R. Goicoechea ; D. Teyssier ; M. Etxaluze ; P.F. Goldsmith ; V. Ossenkopf ; M. Gerin ; E.A. Bergin ; John H. Black (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; J. Cernicharo ; S. Cuadrado ; P. Encrenaz ; E. Falgarone ; A. Fuente ; A. Hacar ; D.C. Lis ; N. Marcelino ; G.J. Melnick ; H.S.P. Müller ; Carina M. Persson (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; J. Pety ; M. Röllig ; P. Schilke ; R. Simon ; R.L. Snell ; J. Stutzki
Astrophysical Journal (0004-637X). Vol. 812 (2015), p. 75.
[Artikel, refereegranskad vetenskaplig]

We present the first ~7.′5 × 11.′5 velocity-resolved (~0.2 km/s) map of the [C II] 158 μm line toward the Orion molecular cloud1 (OMC1) 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 (G0 > 500, nH > 5 × 10^3 cm^−3) and from dense PDRs (G0>~10^4, nH>~10^5 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[CII]/LFIR and LFIR/MGas ratios and show that L[CII]/LFIR 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]/LFIR ratio correlates better with the column density of dust through the molecular cloud than with LFIR/MGas. 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]/LFIR variations through the cloud.

Nyckelord: galaxies: ISM – H II regions – infrared: galaxies – ISM: clouds

Denna post skapades 2015-11-11. Senast ändrad 2015-11-11.
CPL Pubid: 225568


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Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik



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