Metal-strong Inflows at the Outer-galactic-scale of a Quasar

Abstract We present an analysis of the absorption-line system in the Very Large Telescope/Ultraviolet and Visual Echelle Spectrograph spectrum at a redshift of z a = 3.1448 associated with the quasar SDSS J122040.23+092326.96, whose systematic redshift is z e = 3.1380 ± 0.0007, measured from the H β +[O iii ] emission lines in our newly acquired NIR P200/TripleSpec data. This absorbing system, detected in numerous absorption lines, including the N v , N iii , C iv , C iii , Si iv , Si iii , and H i Lyman series, can be resolved into seven kinematic components with redshifted velocities ranging from 200 to 900 km s −1 . The high-ionization N v doublet detected and the rather narrow Lyman series measured ( b ≈ 14 km s −1 ) suggest that the absorption gas is photoionized, possibly by the quasar. A low density is inferred by the fact that N iii λ 989.80 is significantly detected while N iii * λ 991.57 ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mspace width="0.25em"/> <mml:msub> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">c</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>3.3</mml:mn> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi>cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> </mml:math> ) is undetectably weak. A firm lower limit of a solar value to the abundance of the gas can be set based on the measurements of Si iv and H i column densities, as first proposed by F. Hamann. Detailed photoionization simulations indicate that T 1, and possibly the absorber as a whole, has metallicities of Z ∼ 1.5 − 6.0 Z ☉ , and is located at ∼15 kpc from the quasar nucleus. The metal-strong absorption inflows at the outskirt of the quasar host galaxy most likely originated in situ and were driven by stellar processes, such as stellar winds and/or supernova explosions. Such a relatively rare system may hold important clues to understanding the baryonic cycling of galaxies, and more cases could be picked out using relatively strong Si iv and weak Lyman absorption lines.