Submillimeter water and ammonia absorption by the peculiar z~0.89 interstellar medium in the gravitational lens of the PKS 1830-211 system

TL;DR

This study reports the detection of water and ammonia absorption lines in a galaxy at redshift 0.89, providing insights into its interstellar medium and potential for testing fundamental physical constants over cosmic time.

Contribution

First detection of ground-state ammonia and water absorption lines in a galaxy at intermediate redshift using APEX, comparing interstellar medium properties with the Milky Way.

Findings

Detected ortho-ammonia and water lines at z~0.89

Identified differences between extragalactic and Galactic interstellar media

Potential to constrain proton-electron mass ratio variation over 7.2 Gyr

Abstract

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.