2000ApJ...545..234B

We present a study of carbon in N159/N160, an H II region complex in the low-metallicity Large Magellanic Cloud. We have mapped this region, which comprises four distinct molecular clouds spanning a wide range of star formation activity, in four transitions: ¹³CO (J=1⟶0), ¹²CO (J=2⟶1) and (J=4⟶3), and [C I] (³P₁⟶³P₀). Combining these data with existing [C II] (²P_3/2⟶²P_1/2) observations provides a complete picture of the predominant forms of carbon in the gas phase of the ISM. The new CO (J=2⟶1) data show that the complex is immersed in an envelope of extended, low-level emission, undetected by previous (J=1⟶0) mapping efforts. The ¹²CO (J=2⟶1)/(J=1⟶0) ratio in this envelope is ≳3, a value consistent with optically thin CO emission. The envelope is also relatively bright in [C I] and [C II], and calculations show that it is mostly photodissociated: it appears to be translucent (A_V<1). Neutral carbon emission in the complex unexpectedly peaks at the quiescent southern cloud (N159S). In the northern portion of the map (the N160 nebula), the H II regions prominent in [C II] correspond to holes in the [C I] distribution. Overall we find that, while the I_[C II]_/ICO_ ratio is enhanced with respect to similar complexes in the Milky Way, the I_[C I]_/ICO_ ratio appears to be similar or reduced.