A new measure of at redshift from very high resolution spectra of Q 1101–264^*

¹ Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany e-mail: lev@astro.ioffe.rssi.ru
² Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34131 Trieste, Italy
³ Observatoire de Paris, 61 avenue de l'Observatoire, 75014 Paris, France
⁴ Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
⁵ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany

Received: 19 July 2006
Accepted: 26 February 2007

Abstract

Aims.We probe the evolution of the fine-structure constant α with cosmic time.

Methods.Accurate positions of the lines , , and are measured in the z_abs = 1.84 absorption system from a high-resolution (FWHM ~ 3.8 km s^-1) and high signal-to-noise (S/N 100) spectrum of the quasar Q 1101–264 (z_em = 2.15, ), integrated for 15.4 h. The Single Ion Differential α Measurement (SIDAM) procedure and the method are used to set constraints on .

Results.We have found a relative radial velocity shift between the and lines of ± 85 m s^-1 (both random and systematic errors are included), which, if real, would correspond to = 10^-6 ( C.L.). Considering the strong implications of a such variability, additional observations with comparable accuracy at redshift are required to confirm this result.