Proximate damped Lyman-$\alpha$ systems as tracers of quasar feedback

TL;DR

This study investigates proximate damped Lyman-alpha systems near quasars, revealing their kinematic properties and physical states, and linking them to quasar feedback mechanisms like inflows and outflows.

Contribution

It provides a unified framework for classifying proximate absorbers and demonstrates their connection to quasar-driven gas dynamics and feedback processes.

Findings

13% of ProxSys are Ghostly or DLA-Cor with excited species

Classes form a continuum with decreasing absorption strengths and dust content

Standard DLAs are within 1000 km/s, while Ghostly systems show broader velocity ranges

Abstract

Active galactic nuclei (AGN) profoundly affect the interstellar medium of their host galaxies through intense radiation fields and powerful winds. Characterising this feedback is essential for understanding galaxy formation and evolution. Here we revisit the origin of proximate damped Lyman-$\alpha$ absorbers (PDLAs), which trace cold gas within 3000 km/s of the quasar redshift, and interpret their kinematics and physical properties within a unified framework. We searched the SDSS DR16 database for low-ionisation metal absorption-line systems at the quasar redshift (referred to as ProxSys). This approach enables us to identify and classify different types of proximate absorbers, including so-called Ghostly systems, coronagraphic DLAs (DLA-Cor), standard DLAs, and sub-DLAs, based on the presence of strong Lyman-alpha absorption, partial covering signatures, or excited atomic transitions such as SiII*. We find that about 13% of ProxSys belong to the Ghostly or DLA-Cor classes and exhibit strong absorption from excited species. The different classes of ProxSys form a continuous sequence characterised by decreasing SiII*, CIV, and NV absorption strengths and dust content. Their velocity distributions reveal multiple kinematic components. Standard DLAs cluster within 1000km/s of the quasar systemic redshift, consistent with gas in the host galaxy, whereas Ghostly and SiII* bearing systems display broader distributions, including outflows reaching -2000 km/s and a smaller population of inflowing clouds up to +1200 km/s. Median stacked spectra confirm that Ghostly and coronagraphic systems arise in dense, compact gas partially covering the quasar emission regions. These results support a scenario in which cold, dense clouds participate in a dynamic cycle of inflow and outflow in the vicinity of quasars, consistent with chaotic cold accretion.