[1] Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany
[2] OAN, Madrid, Spain
[3] IRAM, Grenoble, France
[4] New Mexico Inst Min & Technol, Socorro, NM USA
[5] Heidelberg Univ, Heidelberg, Germany
[6] Carnegie Inst, Washington, DC USA