2505.01499v1
An extremely metal-poor Lyman $α$ emitter candidate at $z=6$ revealed through absorption spectroscopy
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Archival VLT/MUSE data reveal a Lyα emitter at z=6.0323 just 29 pkpc in front of the quasar PSO J158-14 (z=6.0685), previously missed because it leaves no metal absorption in the quasar spectrum. The Lyα line sits at the edge of the quasar proximity zone, and a proximate sub-DLA with log N_HI≈19.7 reproduces the observed damping wing. Deep (>10 hr) FIRE+X-shooter spectroscopy yields [Z/H] < −3 after ionization-correction modeling, marking this source as an extremely metal-poor galaxy candidate. This system offers a rare window on near-pristine gas and potential Population III signatures during reionization.
Key figures to inspect
- Fig. 1: Inspect the PSF-subtracted MUSE SNR map and spectrum to see the LAE’s position relative to PSO J158-14 and its Lyα line at z=6.0323; compare the sub-DLA damping-wing fit to homogeneous-IGM models and note the absence of other lines in the MUSE range.
- Fig. 2: Use the HST F555W and F850LP non-detections to rule out a low-z interloper and confirm that the measured Lyα flux is consistent with a z≈6 dropout source.
- Fig. 3: Examine the continuum-normalized FIRE+X-shooter J-band stacks at the LAE redshift; the lack of low-ionization metal lines against marked foreground absorbers underpins the stringent metallicity limits.
- Fig. 4: Check the stacked absorption limits versus CLOUDY-based ionization corrections; [Z/H] < −3 remains robust and is only weakly affected by quasar radiation, reinforcing the EMP interpretation.