Carbon in the N159/N160 Complex of the Large Magellanic Cloud

Abstract

We present a study of carbon in N159/N160, an HII 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 (1-0) CO (2-1) and (4-3), and [CI] (1-0). Combining these data with existing [CII] observations provides a complete picture of the predominant forms of carbon in the gas phase of the ISM. The new CO (2-1) data show that the complex is immersed in an envelope of extended, low level emission, undetected by previous (1-0) mapping efforts. The CO (2-1)/(1-0) ratio in this envelope is >~3, a value consistent with optically thin CO emission. The envelope is also relatively bright in [CI] and [CII], and calculations show that it is mostly photodissociated: it appears to be translucent (Av<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 HII regions prominent in [CII] correspond to holes in the [CI] distribution. Overall we find that, while the [CII]/CO ratio is enhanced with respect to similar complexes in the Milky Way, the [CI]/CO ratio appears to be similar or reduced.