Light from Dark Clouds

Cloudshine: New Light on Dark Clouds

We present new deep near-infrared images of dark clouds in the Perseus molecular complex. These images show beautiful extended emission which we model as scattered ambient starlight and name “cloudshine”. The brightness and color variation of cloudshine complicates the production of extinction maps, the best tracer of column density in clouds. However, since the profile of reflected light is es...

Bright Light from Dark Matter

Ammonia in Infrared Dark Clouds

Context. While low mass clouds have been relatively well studied, our picture of high-mass star formation remains unclear. Infrared Dark Clouds appear to be the long sought population of cold and dense aggregations with the potential of harbouring the earliest stages of massive star formation. Up to now there has been no systematic study on the temperature distribution, velocity fields, chemica...

Determining the extinction through dark clouds

We discuss the problem of a consistent determination of the visual extinction to objects in and behind a dark cloud. The use of near-infrared colours is discussed, in particular the H-K colours. We concentrate on the uncertainties, with emphasis on the extinction law and on the intrinsic colours of the young stars embedded in a dark cloud. The cases of the two intensively studied nearby star-fo...

HI Narrow Line Absorption in Dark Clouds

We have used the Arecibo telescope to carry out an unbiased survey of 31 dark clouds in the Taurus/Perseus region for narrow absorption features in HI (λ 21cm) and OH (1667 and 1665 MHz) emission. We detected HI narrow line absorption (HINLA) in about 80% of the clouds that we observed. HINLA and OH emission, observed simultaneously are remarkably well correlated. Spectrally, they have the same...