Stefano Cristiani

INAF-Osservatorio Astronomico di Trieste, Italy

Poster Title: Chemical abundances in quasar host galaxies from narrow absorption line systems

Abstract: We determined C, N and alpha-element relative abundances in the gas surrounding six quasars at an average redshift of < z > ~ 2.4, by studying six narrow associated absorption systems in UVES high-resolution spectra. We found five systems with a metallicity (measured by C/H) consistent or above the solar value. The average is ~ 4 times solar, at least an order of magnitude larger than what found for intervening absorbers. The ionization structure observed in the associated systems is clearly different from that of the intervening ones, indicating that the associated systems are influenced by the strong UV flux from the quasar. There is a possible correlation (anticorrelation) between [N/C] ([Si/C]) and [C/H] of the studied associated systems, and [N/C] >= 0 when [C/H] >= 0. We have compared these observational results with the predictions of a model simulating the joint evolution of quasars and their spheroidal hosts. The agreement turns out to be very good, in particular, the case envisaging massive haloes and high star-formation rates recovers both the correlation between [N/C] and [C/H] and the anticorrelation for [Si/C] vs. [C/H]. Narrow associated absorption systems prove to be powerful tracers of the chemical abundances in gas belonging to high redshift spheroidal galaxies. This same gas is likely going to contribute to the early enrichment of the surrounding intergalactic medium, outflowed by the quasar feedback. A larger statistics, possibly increasing the number of ionisation stages and chemical elements, would allow us to put firm constraints on detailed chemical evolution models of galaxies at high redshifts.

Link to poster: N/A