Submillimeter water and ammonia absorption by the peculiar z~0.89   interstellar medium in the gravitational lens of the PKS 1830-211 system
  Using the Atacama Pathfinder Experiment (APEX) telescope we have detected the rotational ground-state transitions of ortho-ammonia and ortho-water toward the redshift ~0.89 absorbing galaxy in the PKS 1830-211 gravitational lens system. We discuss our observations in the context of recent space-borne data obtained for these lines with the SWAS and Odin satellites toward Galactic sources. We find commonalities, but also significant differences between the interstellar media in a galaxy at intermediate redshift and in the Milky Way. Future high-quality observations of the ground-state ammonia transition in PKS 1830-211, together with inversion line data, will lead to strong constraints on the variation of the proton to electron mass ratio over the past 7.2 Gyr. 
K. M. Menten (MPIfR), R. Guesten (MPIfR), S. Leurini (ESO), S.   Thorwirth (MPIfR), C. Henkel (MPIfR), B. Klein (MPIfR), C. ...