Molecular absorption in galaxies at intermediate redshifts
by
Sebastian Muller(OSO, Chalmers)
→
Europe/Stockholm
FA31
FA31
Description
Absorption line studies in front of bright background quasars offer an unique opportunity to detect rare molecular species in distant galaxies. They also allow to derive accurate molecular column densities in low excitation regions. A score of molecular species have been observed so far in 4 objects, some of which through several rare isotopologues. The isotopic ratios of C, N, O and S have been measured in two galaxies at z=0.89 and z=0.68, showing significant differences with corresponding ratios in the local Universe and revealing the youth of the gas. In addition, the time variability of absorption lines toward the quasar PKS1830-211, with the near disappearance and resurrection of an absorption component within a few year time scale, gives the chance to directly measure the size of molecular clouds at z=0.89. I will mention the use of these molecular absorption lines to constrain variations of fundamental constants, such as the proton-to-electron mass ratio, over cosmological scales, and measurement of the cosmic microwave background temperature at different redshift.