Stringent bounds to spatial variations of the electron-to-proton mass ratio in the Milky Way

Abstract

The ammonia method to probe variations of the electron-to-proton mass ratio, Delta_mu/mu, is applied for the first time to dense prestellar molecular clouds in the Milky Way. Carefully selected sample of 21 NH_3/CCS pairs observed in the Perseus molecular cloud provide the offset Delta V (CCS-NH_3)= 36+/-7_{stat}+/-13.5_{sys} m/s . A similar offset of Delta V = 40.8 +/- 12.9_{stat} m/s between NH_3 (J,K) = (1,1) and N_2H+ J = 1-0 has been found in an isolated dense core L183 by Pagani et al. (2009). Overall these observations provide a safe bound of a maximum offset between ammonia and the other molecules at the level of Delta V < 100 m/s. This bound corresponds to Delta_mu/mu < 1E-7, which is an order of magnitude more sensitive than available extragalactic constraints. Taken at face value the measured Delta V shows positive shifts between the line centers of NH_3 and these two other molecules and suggest a real offset, which would imply a Delta_mu/mu about 4E-8. If Delta_mu/mu follows the gradient of the local gravitational potential, then the obtained results are in conflict with laboratory atomic clock experiments in the solar system by 5 orders of magnitude, thus requiring a chameleon-type scalar field model. New measurements involving other molecules and a wider range of objects along with verification of molecular rest frequencies are currently planned to confirm these first indications.

arXiv comment7 pages +2 figures. Galileo Galilei Institute Conferences on Dark Matter and Dark Energy

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Cited by in corpus (15)

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• Constraining cosmologies with fundamental constants I. Quintessence and K-Essence
• Searching for spatial variations of alpha^2/mu in the Milky Way
• An Environmental Variation of Constants
• Enhanced sensitivity to a possible variation of the proton-to-electron mass ratio in ammonia
• Sensitivity of the isotopologues of hydronium to variation of the electron-to-proton mass ratio
• Sensitivity of Tunneling-Rotational Transitions in Ethylene Glycol to Variation of Electron-to-Proton Mass Ratio
• Space-time variation of the electron-to-proton mass ratio in a Weyl model
• Searching for Chameleon-like Scalar Fields