Metal Enrichment in the Circumgalactic Medium and Ly Halos around Quasars at z ∼ 3

• Published in: The Astrophysical journal 2020-07, Vol.898 (1)
• Main Authors: Guo, Yucheng, Maiolino, Roberto, Jiang, Linhua, Matsuoka, Kenta, Nagao, Tohru, Dors, Oli Luiz, Ginolfi, Michele, Henden, Nick, Bennett, Jake, Sijacki, Debora, Puchwein, Ewald
• Format: Article
• Language: English
• Subjects: Circumgalactic medium; High-redshift galaxies; Quasars
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ab9b7f

Deep observations have detected extended Ly emission nebulae surrounding tens of quasars at redshift 2-6. However, the metallicity of such extended halos is still poorly understood. We perform a detailed analysis on a large sample of 80 quasars at z ∼ 3 based on MUSE-VLT data. We find clear evidence of extended emission of the UV nebular lines such as C iv λ1549 or He ii λ1640 for about 20% of the sample, while C iii] λ1909 is only marginally detected in a few objects. By stacking the cubes, we detect emission of C iv, He ii, and C iii] out to a radius of about 45 kpc. C iv and He ii show a radial decline much steeper than Ly , while C iii] shows a shallower profile similar to Ly in the inner 45 kpc. We infer that the average metallicity of the circumgalactic gas within the central 30-50 kpc is ∼0.5 solar, or even higher. However, we also find evidence of a component of the Ly halos, which has much weaker metal emission lines relative to Ly . We suggest that the high metallicity of the circumgalactic medium within the central 30-50 kpc is associated with chemical pre-enrichment by past quasar-driven outflows and that there is a more extended component of the circumgalactic medium that has much lower metallicity and is likely associated with near-pristine gas accreted from the intergalactic medium. We show that our observational results are in good agreement with the expectations of the FABLE zoom-in cosmological simulations.