Nitrogen-deficient and iron-rich associated absorbers with oversolar metallicities towards the quasar HE0141-3932

Abstract

Abstract. HE0141-3932 (zem = 1.80) is a bright blue radio-quiet quasar which reveals an emission line spectrum with an unusually weak Lyα line. In addition, large redshift differences (∆z = 0.05) are observed between high ionization and low ionization emission lines. Absorption systems identified at z abs = 1.78, 1.71, and 1.68 show mild oversolar metallicities (Z ≈ 1 − 2Z ) and can be attributed to the associated gas clouds ejected from the circumnuclear region. The joint analysis of the emission and absorption lines leads to the conclusion that this quasar is seen almost pole-on. Its apparent luminosity may be Doppler boosted by ∼ 10 times. The absorbing gas shows high abundance of In the absorption spectrum of HE0141-3932 obtained with the VLT/UVES, associated systems are found at z abs = 1.78, 1.71, and 1.68. They exhibit a wealth of metal absorptions including lines of Fe ii. Since these systems arise in gas ejected from the circumnuclear region, careful analysis of the element abundances can produce important clues about the enrichment mechanisms and physical processes leading to the QSO/AGN phenomena. The numbers presented in Table 1 are obtained with the Monte Carlo Inversion (MCI) method -an advanced computational procedure designed to estimate the physical parameters of optically thin absorbers with varying gas density and turbulent velocity field (Levshakov et al. 2000).We conclude the following:• The analyzed absorption systems show high iron content, [Fe/C] = 0.15 ± 0.1, [Fe/Mg] = 0.0 ± 0.1 (z abs =1.78), but at the same time nitrogen is strongly underabundant, [N/C] < ∼ −0.5 (z abs =1.68). These abundances are estimated in different associated systems but they are representative for the bulk of circumnuclear gas since the mass of the stellar population involved in the enrichment of quasar's circumnuclear region is high, > 10 4 M , (Baldwin et al. 2003) and, hence, large metallicity gradients and sharp discontinuities due to enrichment by only a few stars are unlikely.• ; N is given in units of cm −2 ; b estimated abundances are pure illustrative since they are obtained under assumption of the photoionization equilibrium whereas the absorption system is non-equilibrial (see Reimers et al. (2005) for details)iron, the emission line ratios Fe ii/C iv and Fe ii/Mg ii are proposed to be a measure of QSO ages. However, large values of [Fe/C] and [Fe/Mg] are always associated in these models with a considerable overabundance of nitrogen, [N/C] > 0.3. We do not observe such relations in our systems and, hence, do not confirm this 'iron clock' model.• The results obtained are in line with Matteucci & Recchi (2001), who showed that time scale for enrichment by SNe Ia is not unique but a strong function of the adopted stellar lifetimes, initial mass function, and star formation rate and can vary by more than order of magnitude. AcknowledgementsS.A.L. thanks the IAU for the travel grant.