Artikel i vetenskaplig tidskrift, 2015

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.

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


J.R. Goicoechea

D. Teyssier

M. Etxaluze

P.F. Goldsmith

V. Ossenkopf

M. Gerin

E.A. Bergin

John H Black

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

J. Cernicharo

S. Cuadrado

P. Encrenaz

E. Falgarone

A. Fuente

A. Hacar

D. Lis

N. Marcelino

G.J. Melnick

H.S.P. Müller

Carina Persson

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

J. Pety

M. Röllig

P. Schilke

R. Simon

R.L. Snell

J. Stutzki

Astrophysical Journal

0004-637X (ISSN) 1538-4357 (eISSN)

Vol. 812 75-


Astronomi, astrofysik och kosmologi


Grundläggande vetenskaper