Extended and broad Lyman alpha emission around a BAL quasar at z~5

TL;DR

This study presents deep MUSE observations of a z~5 BAL quasar revealing an extensive Lyman alpha nebula, with properties indicating a possible link between nebula size and dark matter halo growth, and evidence of outflowing gas.

Contribution

First detailed analysis of a high-redshift BAL quasar's Lyman alpha nebula, highlighting its size, kinematics, and potential connection to dark matter halo evolution.

Findings

Lyman alpha nebula extends up to ~60 kpc around the quasar.

Nebula appears less extended at z~5 compared to lower redshift when considering surface brightness.

High velocity dispersion suggests outflowing material in the inner CGM.

Abstract

In this work we report deep MUSE observations of a Broad Absorption Line (BAL) quasar at z ~ 5, revealing a Lyman alpha nebula with a maximum projected linear size of ~ 60 kpc around the quasar (down to our 2-sigma SB limit per layer of ~ 9e-19 erg/s/cm^2/arcsec^2 for a 1 arcsec^2 aperture). After correcting for the cosmological surface brightness dimming, we find that our nebula, at z ~ 5, has an intrinsically less extended Lyman alpha emission than nebulae at lower redshift. However, such a discrepancy is greatly reduced when referring to comoving distances, which take into account the cosmological growth of dark matter (DM) haloes, suggesting a positive correlation between the size of Lyman alpha nebulae and the sizes of DM haloes/structures around quasars. Differently from the typical nebulae around radio-quiet non-BAL quasars, in the inner regions (~ 10 kpc) of the circumgalactic medium (CGM) of our source, the velocity dispersion of the Lyman alpha emission is very high (FWHM > 1000 km/s), suggesting that in our case we may be probing outflowing material associated with the quasar.