The multiphase circumgalactic medium in the epoch of reionization: CII and CIV absorbers around [OIII] emitters
Year: 2026
Type: article
Abstract: We investigate the multiphase circumgalactic medium during the epoch of reionization (z>6) by cross-correlating cool- ̧ii and warm-ionized ̧iv absorption systems with star-forming emitters. JWST/NIRCam wide-field slitless spectroscopy from the EIGER survey was combined with medium- and high-resolution optical and NIR spectra of six background quasars, including new VLT/X-Shooter observations of PSO J159-02. We analyzed the relation between 16 ̧ii and 14 ̧iv absorbers (łog(N) > 13.0) and 136 galaxies within an impact parameter of R_⊥ łeq 1000 pkpc and a line-of-sight separation of Δ v łeq 500 ̨ms. We detected a statistically significant excess of both ions around galaxies compared to a randomized background. The ̧iv covering fraction remains enhanced up to ∼ 1 pMpc, whereas ̧ii drops to the background level beyond ∼ 0.5 pMpc, demonstrating that the warm-ionized phase is more spatially extended than cooler gas. Jointly, the 3D galaxy-absorber spatial clustering is significantly weaker than the galaxy-galaxy autocorrelation. This provides direct physical evidence that early carbon enrichment is not confined to the virial radius of massive star-forming systems; rather, a substantial fraction of these metals permeates the diffuse intergalactic medium or is injected by a widespread population of faint undetected dwarf galaxies. Finally, we note a rapid radial decline of the ̧iv covering fraction compared with lower-redshift samples at z<2 and z ≥ 2.8 which indicates an evolving circumgalactic medium ionization structure where early metals predominantly reside in lower ionization states. In conclusion, we determine a conservative lower limit for the observed carbon mass of ̊m M_ ̧ii + ̧iv 10^6 , M_⊙ within 300 pkpc.
Source: Astronomy and Astrophysics
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
OpenAlex ID: W7220463483