[CI], [CII] and CO emission lines as a probe for alpha variations at low and high redshifts

TL;DR

This paper uses emission lines from [CI], [CII], and CO to test for variations in the fine structure constant alpha across different cosmic environments and redshifts, finding no significant changes.

Contribution

It demonstrates the effectiveness of combining emission lines from different species to constrain alpha variations over a wide redshift range, including high redshifts.

Findings

No evidence for alpha variation in the Milky Way cloud L1599B.

Stringent limit on alpha variation in galaxy M33: |Δα/α| < 4×10^-7.

Limits on alpha variation at high redshift: |Δα/α| < 1.3×10^-5.

Abstract

The offsets between the radial velocities of the rotational transitions of carbon monoxide and the fine structure transitions of neutral and singly ionized carbon are used to test the hypothetical variation of the fine structure constant, alpha. From the analysis of the [CI] and [CII] fine structure lines and low J rotational lines of 12CO and 13CO, emitted by the dark cloud L1599B in the Milky Way disk, we find no evidence for fractional changes in alpha at the level of |$\Delta \alpha/\alpha$| < 3*10^-7. For the neighbour galaxy M33 a stringent limit on Delta alpha/alpha is set from observations of three HII zones in [CII] and CO emission lines: |$\Delta \alpha/\alpha$| < 4*10^-7. Five systems over the redshift interval z = 5.7-6.4, showing CO J=6-5, J=7-6 and [CII] emission, yield a limit on |$\Delta \alpha/\alpha$| < 1.3*10^-5. Thus, a combination of the [CI], [CII], and CO emission lines turns out to be a powerful tool for probing the stability of the fundamental physical constants over a wide range of redshifts not accessible to optical spectral measurements.