Stringent Constraints on Fundamental Constant Evolution Using Conjugate 18 cm Satellite OH Lines

Area of Science:

• Cosmology
• Astrochemistry
• Fundamental Physics

Background:

• The fine structure constant (α) and proton-electron mass ratio (μ) are fundamental constants in physics.
• Variations in these constants over cosmic time could indicate new physics.
• Hydroxyl (OH) radio lines offer a unique probe for testing these variations due to their distinct frequency shifts.

Purpose of the Study:

• To constrain the evolution of the quantity μα² over cosmological timescales.
• To test for systematic effects in astronomical measurements of fundamental constants.
• To utilize deep radio astronomy observations of OH lines towards PKS 1413+135.

Main Methods:

• Deep integration observations using the Arecibo Telescope targeting redshifted OH 18 cm lines.
• Analysis of satellite OH 1720 MHz (emission) and 1612 MHz (absorption) lines.
• Nonparametric analysis of line shapes and redshifts to probe changes in α and μ.

Main Results:

• New Arecibo data yield [ΔX/X]=(+0.97±1.52)×10⁻⁶ for X≡μα².
• Combined data from Arecibo and Westerbork Synthesis Radio Telescope give [ΔX/X]=(-1.0±1.3)×10⁻⁶.
• This represents the most stringent constraint on fractional changes in μα² from astronomical spectroscopy to date.

Conclusions:

• No evidence for significant changes in μα² over the last 2.9 billion years.
• The study demonstrates the absence of significant systematic effects in the OH line measurements.
• The results provide strong observational support for the constancy of fundamental physical constants.