Kanekar, N. ; Prochaska, J. X. ; Ellison, S. L. ; Chengalur, J. N. (2010) Probing fundamental constant evolution with neutral atomic gas lines The Astrophysical Journal Letters, 712 (2). L148-L152. ISSN 2041-8205
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Official URL: http://iopscience.iop.org/2041-8205/712/2/L148
Related URL: http://dx.doi.org/10.1088/2041-8205/712/2/L148
Abstract
We have detected narrow HI 21 cm and CI absorption at z ~ 1.4-1.6 toward Q0458-020 and Q2337-011, and use these lines to test for possible changes in the fine structure constant α, the proton-electron mass ratio μ, and the proton gyromagnetic ratio gp . A comparison between the HI 21 cm and CI line redshifts yields ΔX/X = (+6.8 ± 1.0) x 10−6 over 0 < z < 1.46, where X = gp α2/μ, and the errors are purely statistical, from the Gaussian fits. The simple line profiles and the high sensitivity of the spectra imply that statistical errors in this comparison are an order of magnitude lower than in previous studies. Further, the CI lines arise in cold neutral gas that also gives rise to H I 21 cm absorption, and both background quasars are core-dominated, reducing the likelihood of systematic errors due to local velocity offsets between the hyperfine and resonance lines. The dominant source of systematic error lies in the absolute wavelength calibration of the optical spectra, which appears uncertain to ~2 km s−1, yielding a maximum error in ΔX/X of ~6.7 × 10−6. Including this, we obtain ΔX/X = (+6.8 ± 1.0(statistical) ± 6.7(max. systematic)) × 10−6 over 0 < z < 1.46. Using literature constraints on Δμ/μ, this is inconsistent with claims of a smaller value of a from the many-multiplet method, unless fractional changes in gp are larger than those in α and μ.
Item Type: | Article |
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Source: | Copyright of this article belongs to American Astronomical Society. |
Keywords: | Atomic Processes; Galaxies: High-redshift; Quasars: Absorption Lines |
ID Code: | 63552 |
Deposited On: | 29 Sep 2011 04:12 |
Last Modified: | 29 Sep 2011 04:12 |
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