Searching for chameleon-like scalar fields with the ammonia method

Lapinov

Henkel

et al. 2010

A&A

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Context. In our previous work we found a statistically significant offset ΔV ≈ 27 m s −1 between the radial velocities of the HC 3 N J = 2−1 and NH 3 (J, K) = (1, 1) transitions observed in molecular cores from the Milky Way. This may indicate that the electron-toproton mass ratio, μ ≡ m e /m p , increases by ∼3 × 10 −8 when measured under interstellar conditions with matter densities of more than 10 orders of magnitude lower than with laboratory (terrestrial) environments. Aims. We map four molecular cores L1498, L1512, L1517, and L1400K selected from our previous sample to estimate systematic effects in ΔV due to possible velocity gradients or other sources across the cloud and to check the reproducibility of the velocity offsets on the year-to-year time base. Methods. We use the ammonia method, which involves observations of inversion lines of NH 3 complemented by rotational lines of other molecular species and allows us to test changes in μ caused by a higher sensitivity of the inversion frequencies to the μ-variation than with the rotational frequencies. Results. We find that in two cores L1498 and L1512 the NH 3 (1, 1) and HC 3 N (2-1) transitions closely trace the same material and show an offset of ΔV ≡ V lsr (HC 3 N) -V lsr (NH 3 ) = 26.9 ± 1.2 stat ± 3.0 sys m s −1 throughout the entire clouds. The offsets measured in L1517B and L1400K are 46.9 ± 3.3 stat ± 3.0 sys m s −1 and 8.5 ± 3.4 stat ± 3.0 sys m s −1 , respectively, and are, probably, subject to Doppler shifts due to spatial segregation of HC 3 N versus NH 3 . We also determine frequency shifts caused by external electric and magnetic fields and by the cosmic black body radiation-induced Stark effect and find that they are less than 1 m s −1 . Conclusions. The measured velocity offset in L1498 and L1512, when interpreted in terms of Δμ/μ ≡ (μ obs − μ lab )/μ lab , gives Δμ/μ = (26 ± 1 stat ± 3 sys ) × 10 −9 . Although this estimate is based on a limited number of sources and molecular pairs used in the ammonia method, it demonstrates a high accuracy with which the fundamental physics can be tested by means of radio observations. The non-zero signal in Δμ/μ should be further examined as larger and more accurate data sets become available.

Section: Introductionsupporting

confidence: 77%

Searching for chameleon-like scalar fields with the ammonia method

Lapinov

Henkel

et al. 2010

A&A

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“…For comparison, in the Milky Way the [C i]/CO pairs restrict ΔF/F at the level of |ΔF/F| < 0.4 ppm (Levshakov et al 2010a) leading to a limit on |Δα/α| < 0.2 ppm since the spatial variations in μ are restricted to |Δμ/μ| < 0.03 ppm in the disk of the Milky Way (Levshakov et al 2010b;Levshakov et al 2010c;Levshakov et al 2011;Ellingsen et al 2011).…”

Section: Discussionmentioning

confidence: 99%

An upper limit to the variation in the fundamental constants at redshiftz= 5.2

Combes

Boone

et al. 2012

A&A

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Aims. We constrain a hypothetical variation in the fundamental physical constants over the course of cosmic time. Methods. We use unique observations of the CO(7-6) rotational line and the [C i] 3 P 2 − 3 P 1 fine-structure line towards a lensed galaxy at redshift z = 5.2 to constrain temporal variations in the constant F = α 2 /μ, where μ is the electron-to-proton mass ratio and α is the fine-structure constant. The relative change in F between z = 0 and z = 5.2, ΔF/F = (F obs − F lab )/F lab , is estimated from the radial velocity offset, ΔV = V rot − V fs , between the rotational transitions in carbon monoxide and the fine-structure transition in atomic carbon. Results. We find a conservative value ΔV = (1±5) km s −1 (1σ C.L.), which when interpreted in terms of ΔF/F gives ΔF/F < 2×10 −5 . Independent methods restrict the μ-variations at the level of Δμ/μ < 1 × 10 −7 at z = 0.7 (look-back time t z0.7 = 6.4 Gyr). Assuming that temporal variations in μ, if any, are linear, this leads to an upper limit on Δμ/μ < 2 × 10 −7 at z = 5.2 (t z5.2 = 12.9 Gyr). From both constraints on ΔF/F and Δμ/μ , one obtains for the relative change in α the estimate Δα/α < 8 × 10 −6 , which is at present the tightest limit on Δα/α at early cosmological epochs.

“…It was mapped in the [C i] (1-0) line on the KOSMA 3 m submillimeter telescope with a beamwidth of 55 and the velocity resolution of 0.6 km s −1 (Mookerjea et al 2006b). These observations were compared with the 13 CO (1-0) observations (beamsize ∼60 , spectral resolution ∼0.1 km s −1 ) taken from Liszt & Lucas (1999) (1-0) and 13 CO (1-0) spectra are included in …”

Section: Sourcementioning

confidence: 99%

Searching for spatial variations ofα²/μin the Milky Way

Molaro²,

Reimers

2010

A&A

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Aims. We probe the dependence of α 2 /μ on the ambient matter density by means of spectral observations in submm-and mm-wave bands. Methods. A procedure is suggested for exploring the value of F = α 2 /μ, where μ = m e /m p is the electron-to-proton mass ratio, and α = e 2 /( c) is the fine-structure constant. The fundamental physical constants, which are measured in different physical environments of high (terrestrial) and low (interstellar) densities of baryonic matter are supposed to vary in chameleon-like scalar field models, which predict that both masses and coupling constant may depend on the local matter density. The parameter ΔF/F = (F obs − F lab )/F lab can be estimated from the radial velocity offset, ΔV = V rot − V fs , between the low-laying rotational transitions in carbon monoxide 13 CO and the fine-structure transitions in atomic carbon [C i]. A model-dependent constraint on Δα/α can be obtained from ΔF/F using Δμ/μ independently measured from the ammonia method. Results. Currently available radio astronomical datasets provide an upper limit on |ΔV| < 110 m s −1 (1σ). When interpreted in terms of the spatial variation of F, this gives |ΔF/F| < 3.7 × 10 −7 . An order of magnitude improvement in this limit will allow us to independently test a non-zero value of Δμ/μ = (2.2 ± 0.4 stat ± 0.3 sys ) × 10 −8 , recently found with the ammonia method. Considering that the ammonia method restricts the spatial variation of μ at the level of |Δμ/μ| ≤ 3 × 10 −8 and assuming that ΔF/F is the same in the entire interstellar medium, one obtains that the spatial variation of α does not exceed the value |Δα/α| < 2 × 10 −7 . Since extragalactic gas clouds have similar densities to those in the interstellar medium, the bound on Δα/α is also expected to be less than 2 × 10 −7 at high redshift if no significant temporal dependence of α is present.