1. Centre for Star and Planet Formation, Natural History Museum of Denmark and the Niels Bohr Institute, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark
2. Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA
3. Department of Astronomy & Physics, Saint Mary’s University, Halifax, Nova Scotia B3H 3C 3, Canada