Publication Date:
2014-01-16
Description:
Quasar spectra reveal a rich array of important astrophysical information about galaxies which intersect the quasar line of sight. They also enable tests of the variability of fundamental constants over cosmological time- and distance-scales. Key to these endeavours are the laboratory frequencies, isotopic and hyperfine structures of various metal-ion transitions. Here, we review and synthesize the existing information about these quantities for 43 transitions which are important for measuring possible changes in the fine-structure constant, α, using optical quasar spectra, i.e. those of Na, Mg, Al, Si, Ca, Cr, Mn, Fe, Ni and Zn. We also summarize the information currently missing that precludes more transitions being used. We present an up-to-date set of coefficients, q , which define the sensitivity of these transitions to variations in α. New calculations of isotopic structures and q -coefficients are performed for ${\rm Si\,{\small{ II}}}$ and ${\rm Ti\,{\small{ II}}}$ , including ${\rm Si\,\small{ II}}$ 1808 and ${\rm Ti\,{\small{ II}}}$ 1910.6/1910.9 for the first time. Finally, simulated absorption-line spectra are used to illustrate the systematic errors expected if the isotopic/hyperfine structures are omitted from profile fitting analyses. To ensure transparency, repeatability and currency of the data and calculations, we supply a comprehensive data base as Supporting Information. This will be updated as new measurements and calculations are performed.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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