Proximate damped Lyman-α systems as tracers of quasar feedback

Active galactic nuclei (AGNs) 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-α absorbers (PDLAs), which trace cold gas within 3000 ̨ms of the quasar redshift, and we 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 enabled us to identify and classify different types of proximate absorbers, including so-called ghostly DLAs, coronagraphic DLAs (DLA-Cor), standard DLAs, and sub-DLAs, based on the presence of strong Lyman-α absorption, partial covering signatures, or excited atomic transitions such as Si ii *. We find that about 13% of ProxSys belong to the ghostly DLAs or DLA-Cor classes and exhibit strong absorption from excited species. The different classes of ProxSys form a continuous sequence characterised by decreasing Si ii *$, C iv , and N v absorption strengths and dust content. Their velocity distributions reveal multiple kinematic components. Standard DLAs cluster within pm1000 ̨ms of the quasar systemic redshift, consistent with gas in the host galaxy, whereas ghostly DLAs and Si ii ^*-bearing systems display broader distributions, including outflows reaching -2000 ̨ms and a smaller population of inflowing clouds up to $+1200 ̨ms. Median stacked spectra confirm that ghostly DLAs 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.