Bounds on the fine structure constantvariability from Fe ii absorption lines in QSO spectra

Molaro, P.; Reimers, D.; Agafonova, I. I.; Levshakov, S. A.

doi:10.1140/epjst/e2008-00818-4

Cited by 77 publications

(89 citation statements)

References 33 publications

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“…Following this approach Molaro et al (2008) compared the positions of individual lines measured in the spectra of asteroids and in the solar atlas. This is not possible in the near ultra-violet, where the line blending in the solar spectrum is so high that positions of individual lines cannot be measured.…”

Section: Solar-asteroid Comparisonmentioning

confidence: 99%

Fundamental constants and high‐resolution spectroscopy

et al. 2014

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Absorption-line systems detected in high resolution quasar spectra can be used to compare the value of dimensionless fundamental constants such as the fine-structure constant, α , and the proton-to-electron mass ratio, µ = mp/me, as measured in remote regions of the Universe to their value today on Earth. In recent years, some evidence has emerged of small temporal and also spatial variations in α on cosmological scales which may reach a fractional level of ≈ 10 ppm (parts per million). We are conducting a Large Programme of observations with the Very Large Telescope's Ultraviolet and Visual Echelle Spectrograph (UVES), and are obtaining high-resolution (R ≈ 60 000) and high signal-to-noise ratio (S/N ≈ 100) spectra calibrated specifically to study the variations of the fundamental constants. We here provide a general overview of the Large Programme and report on the first results for these two constants, discussed in detail in Molaro et al. and Rahmani et al.A stringent bound for ∆α/α is obtained for the absorber at z abs = 1.6919 towards HE 2217-2818. The absorption profile is complex with several very narrow features, and is modeled with 32 velocity components. The relative variation in α in this system is +1.3 ± 2.4stat ± 1.0sys ppm if Al II λ 1670Å and three Fe II transitions are used, and +1.1 ±2.6stat ppm in a slightly different analysis with only Fe II transitions used. This is one of the tightest bounds on α-variation from an individual absorber and reveals no evidence for variation in α at the 3-ppm precision level (1-σ confidence). The expectation at this sky position of the recently-reported dipolar variation of α is (3.2-5.4) ± 1.7 ppm depending on dipole model used and this constraint of ∆α/α at face value is not supporting this expectation but not inconsistent with it at the 3σ level. For the proton-to-electron mass ratio the analysis of the H2 absorption lines of the z abs ≈ 2.4018 damped Lyα system towards HE 0027-1836 provides ∆µ/µ = (−7.6 ± 8.1stat ± 6.3sys) ppm which is also consistent with a null variation. The cross-correlation analysis between individual exposures taken over three years and comparison with almost simultaneous asteroid observations revealed the presence of a possible wavelength dependent velocity drift as well as of inter-order distortions which probably dominate the systematic error and are a significant obstacle to achieve more accurate measurements.

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Section: Solar-asteroid Comparisonmentioning

confidence: 99%

Fundamental constants and high‐resolution spectroscopy

et al. 2014

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“…Furthermore, absorption lines from the quasi-stellar objects (QSO) are used for laboratory testing the temporal variation of the fine structure constant (α e = e 2 / c) on the cosmological time scale (Webb et al 2011;King et al 2012;Chand et al 2008;Levshakov et al 2008b,a;Molaro et al 2008). The ground state of the considered ions have the fine structure splitting and the next excited s-state will decay to these fine-structure levels by the allowed transition.…”

Section: Introductionmentioning

confidence: 99%

Spectral properties of a few F-like ions

Nandy

Sahoo

2014

A&A

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Aims. We intend to provide accurate data for the oscillator strengths, transition probabilities, lifetimes, and hyperfine shifts of the atomic energy levels in the fluorine (F)-like Ti, V, Cr, Mn, Co, Ni, Cu, Zn, and Mo ions for the diagnostic of the astrophysical plasma. Furthermore, we propose these ions for probing possible variation in the fine structure constant (α e ) by observing their transition lines from the distant astronomical objects. Methods. We have employed an all-order perturbative method in the relativistic coupled-cluster framework using the Dirac-Coulomb Hamiltonian for calculating the atomic wave functions in the considered F-like ions. We adopted the Fock-space formalism to account for the correlation effects among the occupied electrons by allowing all possible singly and doubly excited configurations in two steps: first considering the correlations between the electrons in a closed-shell configuration, and second constructing the openshell configurations of the first three low-lying states in the considered atomic systems by removing the respective electron from the core orbitals. This procedure enormously simplifies the computational complexity and overcomes the need to select important configuration state functions in determining the atomic state functions in contrast to a truncated configuration interaction method. Moreover, corrections from the frequency-independent Breit interaction and the lowest order quantum electrodynamic effects are incorporated self-consistently. Results. We present the calculated ionization potential energies of the electrons that are detached to form the above considered F-like ions. The correctness of our estimated results are ensured by comparing them with the available experimental values and other calculations. From these calculations, we evaluate the relativistic sensitivity coefficients that we propose here to be used for probing possible temporal variation of the fine structure constant (α e ) through the precise astrophysical observation of the spectral lines of the transitions involving the above low-lying states. The accuracies of these sensitivity coefficients are appraised from the comparison of our calculated energies with the experimental values. We also present the line strengths by calculating the reduced matrix elements of the allowed transitions and of the M1 and E2 forbidden transitions. By combining our calculated line strengths with the observed wavelengths, we determine the oscillator strengths, transition probabilities, and lifetimes of the first two excited states of the above ions and compare them with the other theoretical calculations. The hyperfine splittings of the states are also presented by calculating their magnetic dipole and electric quadrupole hyperfine structure constants.

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“…Their conclusion is that these systematic uncertainties make it difficult to use Keck/HIRES QSO spectra to constrain the change in the fine structure constant at the 10 −6 level. The most stringent constraint on |Δα/α| < 2 ppm was found from the Fe ii lines at z = 1.15 towards the bright quasar HE 0515-4414 (Quast et al 2004;Levshakov et al 2005;Molaro et al 2008). Bounds on μ variations are most effectively obtained from observations of the Werner and Lyman series of the molecular hydrogen H 2 in damped Ly-α systems (DLA).…”

Section: Introductionmentioning

confidence: 99%

Searching for chameleon-like scalar fields with the ammonia method

Levshakov

Molaro

Lapinov

et al. 2010

A&A

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Aims. We probe the dependence of the electron-to-proton mass ratio, μ = m e /m p , on the ambient matter density by means of radio astronomical observations. Methods. The ammonia method, which has been proposed to explore the electron-to-proton mass ratio, is applied to nearby dark clouds in the Milky Way. This ratio, which is measured in different physical environments of high (terrestrial) and low (interstellar) densities of baryonic matter is supposed to vary in chameleon-like scalar field models, which predict strong dependences of both masses and coupling constant on the local matter density. High resolution spectral observations of molecular cores in lines of NH 3 (J, K) = (1, 1), HC 3 N J = 2−1, and N 2 H + J = 1−0 were performed at three radio telescopes to measure the radial velocity offsets, ΔV ≡ V rot − V inv , between the inversion transition of NH 3 (1,1) and the rotational transitions of other molecules with different sensitivities to the parameter Δμ/μ ≡ (μ obs − μ lab )/μ lab . Results. The measured values of ΔV exhibit a statistically significant velocity offset of 23 ± 4 stat ± 3 sys m s −1 . When interpreted in terms of the electron-to-proton mass ratio variation, this infers that Δμ/μ = (2.2 ± 0.4 stat ± 0.3 sys ) × 10 −8 . If only a conservative upper bound is considered, then the maximum offset between ammonia and the other molecules is |ΔV| ≤ 30 m s −1 . This provides the most accurate reference point at z = 0 for Δμ/μ of |Δμ/μ| ≤ 3 × 10 −8 .

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Bounds on the fine structure constantvariability from Fe ii absorption lines in QSO spectra

Cited by 77 publications

References 33 publications

Fundamental constants and high‐resolution spectroscopy

Fundamental constants and high‐resolution spectroscopy

Spectral properties of a few F-like ions

Searching for chameleon-like scalar fields with the ammonia method

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