Indications of Electron-to-proton Mass Ratio Variations in the Galaxy. II. 3 mm Methanol Lines Toward Sgr B2(N) and (M)

Differential measurements of the fundamental constant μ = m e / m p (the electron-to-proton mass ratio) for two sources near the Galactic Center – the Sgr B2(N) and B2(M) molecular clouds – suggest that μ is lower in these clouds than its laboratory value. Based on observations of methanol (CH 3 OH) emission lines in the 80–112 GHz range (data from the IRAM 30-m telescope), a weighted mean value 〈Δμ/μ〉 ≡ 〈(μ obs – μ lab )/μ lab 〉 = (–2.1 ± 0.6) × 10 –7 (1σ) was obtained for Sgr B2(N) at the sample size n = 9. This value of Δμ/μ has the same sign as the result of recent measurements of methanol lines in the higher frequency range of 542–543 GHz (data from the Herschel space telescope) for Sgr B2(N): 〈Δμ/μ〉 = (–4.2 ± 0.7) × 10 –7 (sample size n = 2).