High-resolution Molecular Spectroscopy Of H2 At 10% The Age Of The Universe; Testing The Constancy Of Physical Law

Abstract

Spectroscopy has taught us that atoms and molecules are the same now as they were in the early Universe. This means that the nature of the fundamental forces, and the chemical bonds that derive from the strength of the electromagnetic force, have not changed over cosmological history. High-resolution spectroscopy of molecules in far-distant galaxies is currently applied to tighten the constraints on the constancy of physical law, which is expressed in terms of the constancy of the fundamental constants, i.e. the fine-structure constant $\alpha$ and the proton-electron mass ratio $\mu$. H$_2$ observable at redshifts $z =2-4$, corresponding to look-back times of 10-12 billion years, is sensitive to probe a possible variation of $\mu$. We have examined a number of high redshift objects, Q0405-443 at $z=2.59$, Q0347-383 at $z=3.02$, Q0528-250 at $z=2.81$, Q2123-005 at $z=2.06$, Q2348-011 at $z=2.42$, and Q0642-504 at $z=2.66$ to constrain $\Delta\mu/\mu$. Currently work is in progress to analyze spectra of additional objects Q1237+064 at $z=2.69$, in which also CO is observed, and Q1441+272, which is the highest redshift object (at $z=4.22$) in which H$_2$ is abundantly detected. From the combined studies it follows that $\mu$ varies by less than $10^{-5}$ for look back times of 90\% of the age of the Universe.