Probing fundamental constant evolution with redshifted radio lines

Probing fundamental constant evolution with astronomical spectroscopy

Measuring Changes in the Fundamental Constants with Redshifted Radio Absorption Lines

Strong evidence has recently emerged for a variation in the fine structure constant, α ≡ e/h̄c, over the history of the Universe. This was concluded from a detailed study of the relative positions of redshifted optical quasar absorption spectra. However, radio absorption lines at high redshift offer a much higher sensitivity to a cosmological change in α than optical lines. Furthermore, through ...

Probing the Evolution Ofgalaxies Using Redshifted Hα Emission

In this paper we review the present status and implications of Hα surveys at various redshifts. With the advent of sensitive wide-format near-infrared detectors on large telescopes, deep and extensive Hα surveys are now feasible to redshift z ∼ 2.5. The cosmic star formation history can therefore be traced out to this redshift using Hα alone, avoiding complications arising from the comparison o...

Length—Evolution from Measurement Standard to a Fundamental Constant

The meter had its origin in August of 1793 when the Republican Government of France decreed the unit of length to be 10 of the earth's quadrant passing through Paris and that the unit be called the meter. Five years later, the survey of the arc was completed and three platinum standards and several iron copies of the meter were made. Subsequent examination showed the length of the earth's quadr...

Probing variations in fundamental constants with radio and optical quasar absorption-line observations

Nine quasar absorption spectra at 21-cm and ultraviolet (UV) rest-frame wavelengths are used to estimate possible variations in x ≡αgpμ, where α is the fine structure constant, gp the proton g-factor and μ ≡ me/mp is the electron-to-proton mass ratio. We find 〈 x/x〉 total = (0.63 ± 0.99) × 10−5 over a redshift range 0.23 zabs 2.35 which corresponds to look-back times of 2.7–10.5 billion years. ...