Methanol absorption in PKS B1830-211 at milliarcsecond scales

Abstract

Observations of the frequencies of different rotational transitions of the methanol molecule have provided the most sensitive probe to date for changes in the proton-to-electron mass ratio, over space and time. Using methanol absorption detected in the gravitational lens system PKS B1830-211, changes in the proton-to-electron ratio over the last 7.5 billion years have been constrained to a fractional change less than 1.1e-07. Molecular absorption systems at cosmological distances present the best opportunity for constraining or measuring changes in the fundamental constants of physics over time, however, we are now at the stage where potential differences in the morphology of the absorbing systems and the background source, combined with their temporal evolution, provide the major source of uncertainty in some systems. Here we present the first milliarcsecond resolution observations of the molecular absorption system towards PKS B1830-211. We have imaged the absorption from the 12.2-GHz transition of methanol (which is redshifted to 6.45 GHz) toward the southwestern component and show that it is possibly offset from the peak of the continuum emission and partially resolved on milliarcsecond scales. Future observations of other methanol transitions with similar angular resolution offer the best prospects for reducing systematic errors in investigations of possible changes in the proton-to-electron mass ratio on cosmological scales.

8 pages, 3 figures, accepted for publication in MNRAS

References in corpus (5)

• Probing isotopic ratios at z = 0.89: molecular line absorption in front of the quasar PKS 1830-211
• An ALMA Early Science survey of molecular absorption lines toward PKS1830-211 -- Analysis of the absorption profiles
• Constraints on changes in the proton-electron mass ratio using methanol lines
• Drastic changes in the molecular absorption at redshift z=0.89 toward the quasar PKS 1830-211
• The inhomogeneous ISM toward PKS1830-211 SW - A detailed view on molecular gas at a look-back time of 7.5 Gyr

Cited by in corpus (3)

• A study of submillimeter methanol absorption toward PKS1830-211: Excitation, invariance of the proton-electron mass ratio, and systematics
• Testing the weak equivalence principle by differential measurements of fundamental constants in the Magellanic Clouds
• [CI], [CII] and CO emission lines as a probe for alpha variations at low and high redshifts