Fine-structure transitions as a tool for studying variation of α at high redshifts

Star-forming galaxies at high redshifts are the ideal targets to probe the hypothetical variation of the fine-structure ( FS) constant alpha over cosmological time-scales. We propose a modification of the alkali doublets method that allows us to search for variation in alpha combining far-infrared and submillimetre spectroscopic observations. This variation manifests as velocity offsets between the observed positions of the FS and gross-structure transitions when compared to laboratory wavelengths. Here we describe our method whose sensitivity limit to the fractional changes in a is about 5 x 10(-7). We also demonstrate that current spectral observations of hydrogen and [C II] 158 mu m lines provide an upper limit on | Delta alpha/alpha| less than or similar to 6 x 10(-5) at redshifts z = 3.1 and 4.7.