Letter to the Editor

VLT/UVES constraints on the carbon isotope ratio C/C at z = 1.15 toward the quasar HE 0515–4414

¹ Department of Theoretical Astrophysics, Ioffe Physico-Technical Institute, 194021 St. Petersburg, Russia 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 Sobolev Astronomical Institute, St. Petersburg State University, 198504 St. Petersburg, Russia

Received: 20 September 2005
Accepted: 4 January 2006

Abstract

Context. Aims.We analyzed the lines associated with the damped Lyα system observed at = 1.15 in the spectrum of HE 0515–4414 to derive the ¹²C/¹³C  ratio. Methods. The spectrum was obtained by means of the UV-Visual Echelle Spectrograph (UVES) at the ESO Very Large Telescope (VLT). Results.The obtained lower limit ¹²C/¹³C (2σ C.L.) shows for the first time that the abundance of ¹³C in the extragalactic intervening clouds is very low. This rules out a significant contribution from intermediate-mass stars to the chemical evolution of matter sampled by this line of sight. The estimated low amount of ¹³C is in agreement with low abundances of nitrogen observed in damped Lyα systems – the element produced in the same nuclear cycles and from about the same stars as ¹³C. Conclusions.