Isotopic abundance of carbon in the DLA towards QSO B1331 + 170

Abstract

Chemical evolution models predict a gradual build-up of 13 C in the Universe, based on empirical nuclear reaction rates and assumptions on the properties of stellar populations. Ho we ver, old metal-poor stars within the Galaxy contain more 13 C than is predicted, suggesting that further refinements to the models are necessary. Gas at high-redshift provides important supplementary information at metallicities -2 ≲ [ Fe / H ] ≲ -1, for which there are only a few measurements in the Galaxy. We obtained new, high-quality, VLT/ESPRESSO observations of the QSO B1331 + 170 and used them to measure 12 C/ 13 C in the damped Lyman- αsystem (DLA) at z abs = 1 . 776, with [ Fe / H ] = -1.27. AI-VPFIT , an artificial intelligence tool based on genetic algorithms and guided by a spectroscopic information criterion, was used to explore different possible kinematic structures of the carbon gas. Three hundred independent AI-VPFIT models of the absorption system were produced using pre-set 12 C/ 13 C values, ranging from 4 to 500. Our results show that 12 C/ 13 C = 28 . 5 + 51 . 5 -10 . 4 , suggesting a possibility of 13 C production at low metallicity.