Ghostly DLAs in SDSS DR16
Abstract
In Petitjean (2026, A&A 710, 340), we revisited the origin of proximate damped Lyman-alpha absorbers (PDLAs), which trace cold gas within 3000 km/s of the quasar redshift, and interpreted their kinematics and physical properties within a unified framework. We showed that most PDLAs are associated with the environment of the AGN and/or the quasar host galaxy. We also provided the first census and characterization of absorption systems exhibiting strong absorption from excited levels of atomic ground states among quasar-associated absorbers. Among these, ghostly and coronagraphic systems arise in dense, compact gas that partially covers the quasar emission regions. Most systems are associated with outflows reaching velocities up to -2000 km/s, while a smaller fraction of inflowing clouds extends to velocities of up to +1200 km/s. In the present work, we provide an updated classification of PDLAs, including a revised catalogue of ghostly systems that more than doubles the number of previously known detections. We investigate the properties of these systems by measuring and discussing the equivalent widths of the detected absorption lines in both stacked spectra and individual ghostly systems. In particular, we show that although most ghostly systems are bona fide DLAs, this is not always the case.
Versions
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BibTeX
@misc{petitjean2026ghostly,
title = {{Ghostly DLAs in SDSS DR16}},
author = {Patrick Petitjean},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2606.06270},
eprint = {2606.06270},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.06270},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Ghostly DLAs in SDSS DR16
AU - Patrick Petitjean
PY - 2026
DA - 2026/08/15
PB - arXiv
DO - 10.48550/arxiv.2606.06270
UR - https://arxiv.org/abs/2606.06270
AB - In Petitjean (2026, A&A 710, 340), we revisited the origin of proximate damped Lyman-alpha absorbers (PDLAs), which trace cold gas within 3000 km/s of the quasar redshift, and interpreted their kinematics and physical properties within a unified framework. We showed that most PDLAs are associated with the environment of the AGN and/or the quasar host galaxy. We also provided the first census and characterization of absorption systems exhibiting strong absorption from excited levels of atomic ground states among quasar-associated absorbers. Among these, ghostly and coronagraphic systems arise in dense, compact gas that partially covers the quasar emission regions. Most systems are associated with outflows reaching velocities up to -2000 km/s, while a smaller fraction of inflowing clouds extends to velocities of up to +1200 km/s. In the present work, we provide an updated classification of PDLAs, including a revised catalogue of ghostly systems that more than doubles the number of previously known detections. We investigate the properties of these systems by measuring and discussing the equivalent widths of the detected absorption lines in both stacked spectra and individual ghostly systems. In particular, we show that although most ghostly systems are bona fide DLAs, this is not always the case.
ER -