The Multiphase CGM in the Epoch of Reionization: CII and CIV absorbers around [OIII] Emitters

Abstract

We investigate the multiphase circumgalactic medium (CGM) during the Epoch of Reionization (EoR, $z>6$) by cross-correlating cool- CII and warm-ionized CIV absorption systems with star-forming [OIII] emitters. JWST/NIRCam wide-field slitless spectroscopy from the EIGER survey is combined with medium- and high-resolution optical/NIR spectra of six background quasars, including new VLT/X-Shooter observations of PSO J159-02. We analyze the relation between 16 CII and 14 CIV absorbers ($\log (N)>13.0$) and 136 galaxies, within an impact parameter of R${}_{\perp }\le$ 1000 pkpc and a line-of-sight separation of $\Delta v\le 500$ km/s. We detect a statistically significant excess of both ions around galaxies compared to a randomized background. We observe that the CIV covering fraction remains enhanced up to $\sim 1$ pMpc, whereas CII drops to the background level beyond $\sim 0.5$ 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 auto-correlation. 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 (IGM) or is injected by a widespread population of faint, undetected dwarf galaxies. Finally, we note a rapid radial decline of the CIV covering fraction compared with lower redshift samples at $z<2$ and $z\sim 3-4$ pointing out an evolving CGM ionization structure where early metals reside predominantly in lower ionization states. In conclusion, we determine a conservative lower limit for the observed carbon mass of ${\mathrm{M}}_{\mathrm{CII}+\mathrm{CIV}}\ge 2.8\times 10^6{\mathrm{M}}_{\odot }$ within 300 pkpc.

Accepted for publication in A&A