Author: Andrew Humphrey
Using long-slit optical spectroscopy obtained at the 10.4 m Gran Telescopio Canarias, we have examined the gaseous environment of the radio-loud quasar TXS 1436+157 (z = 2.54),previously known to be associated with a large Lyαnebula and a spatially extended Lyα-absorbing structure. From the Lyαnebula, we measure kinematic properties consistent withinfall at a rate of ∼10–100 M⊙ yr⁻¹ – more than sufficient to power a quasar at the top of theluminosity function.The absorbing structure lies outside of the Lyαnebula, at a radius of ≳40 kpc from thequasar. Against the bright unresolved continuum and line emission from the quasar, we detectin absorption the NVλλ1239, 1241, CIVλλ1548, 1551 and Si IVλλ1394, 1403 doublets, withno unambiguous detection of absorption lines from any low-ionization species of metal. Themetal column densities, taken together with the HI column density measurement from the literature, indicate that the absorbing gas is predominantly ionized by the quasar, has a massof hydrogen of ≳1.6 × 10¹¹ M⊙, a gas density of ≤18 cm⁻³, a line-of-sight thickness of≥18 pc and a covering factor approaching unity. While this absorbing structure is clearly notcomposed of pristine gas, it has an extremely low metallicity, with ionizationmodels providinga 3σ limit of 12+log(O/H) ≤ 7.3.To explain these results, we discuss a scenario involving starburst-driven superbubbles andthe creation of infalling filaments of cold gas which fuel/trigger the quasar. We also discussthe possibility of detecting large-scale absorbers such as this in emission when illuminated bya powerful quasar.
Galaxies: active Galaxies: evolution Galaxies: ISM Quasars: absorption lines Qasars: emission lines Quasars: individual: TXS 1436+157 CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA ASTRONOMÍA Y ASTROFÍSICA