Extended Ly$\alpha$ emission around quasars with eclipsing damped Ly$\alpha$ systems

TL;DR

This study observes extended Lyα emission around high-redshift quasars with eclipsing DLAs, revealing correlations with envelope size and ionization likely driven by the AGN, and suggests infalling gas accretion onto host galaxies.

Contribution

First detection of spatially extended Lyα envelopes around quasars with eclipsing DLAs, highlighting their properties and potential gas accretion mechanisms.

Findings

Extended Lyα envelopes span 26-51 kpc.

Envelope luminosity correlates with spatial extent.

DLAs show low metallicity and signs of ionization by AGN.

Abstract

We present spectroscopic observations of six high redshift ($z_{\rm em}$ $>$ 2) quasars, which have been selected for their Lyman $\alpha$ (Ly$\alpha$) emission region being only partially covered by a strong proximate ($z_{\rm abs}$ $\sim$ $z_{\rm em}$) coronagraphic damped Ly$\alpha$ system (DLA). We detected spatially extended Ly$\alpha$ emission envelopes surrounding these six quasars, with projected spatial extent in the range 26 $\le$ $d_{\rm Ly\alpha}$ $\le$ 51 kpc. No correlation is found between the quasar ionizing luminosity and the Ly$\alpha$ luminosity of their extended envelopes. This could be related to the limited covering factor of the extended gas and/or due to the AGN being obscured in other directions than towards the observer. Indeed, we find a strong correlation between the luminosity of the envelope and its spatial extent, which suggests that the envelopes are probably ionized by the AGN. The metallicity of the coronagraphic DLAs is low and varies in the range $-$1.75 $<$ [Si/H] $<$ $-$0.63. Highly ionized gas is observed to be associated with most of these DLAs, probably indicating ionization by the central AGN. One of these DLAs has the highest AlIII/SiII ratio ever reported for any intervening and/or proximate DLA. Most of these DLAs are redshifted with respect to the quasar, implying that they might represent infalling gas probably accreted onto the quasar host galaxies through filaments.