2003/10/31 by Nissim Kanekar, Jayaram N. Chengalur, Jayaram N Chengalur · 1 citation
Physics and Astronomy · #Absorption (acoustics) #Absorption spectroscopy #Astronomy #Astrophysics #Astrophysics and Cosmic Phenomena #Astrophysics and Star Formation Studies #Atomic physics #Galaxy #Line (geometry) #Measure (data warehouse) #Optics #Physics #Redshift #Sensitivity (control systems) #Spectral line #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2004.07828.x
published as Mon.Not.Roy.Astron.Soc. 350 (2004) L17 · 5 pages, no figures. MNRAS (Letters), in press
openalex publication_date 2004/04/21 · arxiv created 2004/05/05 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We describe a new technique to measure variations in the fundamental parameters α and y≡me/mp, using the sum of the frequencies of cm‐wave OH ‘main’ lines. The technique is ∼ three orders of magnitude more sensitive than that of Chengalur & Kanekar, which utilized only the four 18‐cm OH lines. The increase in sensitivity stems from the use of OH ‘main’ lines arising from different rotational states, instead of the frequency difference between lines from the same state. We also show that redshifts of the main OH 18‐ and 6‐cm lines can be combined with the redshift of an HCO+ transition to measure any evolution in α and y. Both 18‐cm main lines and a number of HCO+ lines have already been detected in absorption in four cosmologically distant systems; the detection of the main 6‐cm OH line in any of these systems would thus be sufficient to simultaneously constrain changes in α and y between the absorption redshift and today.