A [C II] 158$\mu$m Emitter Associated with an OI Absorber at the End of the Reionization Epoch

TL;DR

This study reports the detection of a [C II] 158μm emitter associated with an OI absorber at z≈6, providing insights into the properties of early galaxy environments and the circumgalactic medium during reionization.

Contribution

First detection of a [C II] emitter linked to an OI absorber at high redshift, revealing the nature of early metal-enriched circumgalactic environments.

Findings

[C II] luminosity measured at 7.0×10^7 solar luminosities

OI absorbers may be in massive halos 10-100 times larger than expected

Impact parameter between absorber and emitter is 20 kpc

Abstract

The physical and chemical properties of the circumgalactic medium (CGM) at $z\gtrsim6$ have been studied successfully through the absorption in the spectra of background Quasi-Stellar Objects (QSOs). One of the most crucial questions is to investigate the nature and location of the source galaxies that give rise to these early metal absorbers. Theoretical models suggest that momentum-driven outflows from typical star-forming galaxies can eject metals into the CGM and the intergalactic medium (IGM) at z=5-6. Deep, dedicated surveys have searched for Ly$\alpha$ emission associated with strong CIV absorbers at $z\approx 6$, but only a few Ly$\alpha$ emitter candidates have been detected. Interpreting these detections is moreover ambiguous because Ly$\alpha$ is a resonant line, raising the need for complementary techniques for detecting absorbers' host galaxies. Here, using Atacama Large Millimeter Array (ALMA), we report a [C II] 158$\mu$m emitter associated with a strong low-ionization absorber, OI, at $z=5.978$. The projected impact parameter between OI and [C II] emitter is 20.0 kpc. The measured [C II] luminosity is $7.0\times 10^7$ solar luminosities. Further analysis indicates that strong OI absorbers may reside in the circumgalactic medium of massive halos one to two orders of magnitude more massive than expected values.