Statistical Correlation between the Distribution of Lyα Emitters and Intergalactic Medium H i at z ∼ 2.2 Mapped by the Subaru/Hyper Suprime-Cam

Abstract

Abstract The correlation between neutral hydrogen (H i ) in the intergalactic medium (IGM) and galaxies attracts great interest. We select four fields that include several coherently strong Ly α absorption systems at z ∼ 2.2 detected using background quasars from the whole SDSS/(e) Baryon Oscillation Spectroscopic Survey (BOSS) database. Deep narrowband and g -band imaging are performed using the Hyper Suprime-Cam on the Subaru Telescope. We select 2642 Ly α emitter (LAE) candidates at z = 2.177 ± 0.023 down to the Ly α luminosity of L Ly α ≈ 2 × 10 42 erg s −1 to construct the galaxy overdensity maps, covering an effective area of 5.39 deg 2 . Combining the sample with the Ly α absorption estimated from 64 (e) BOSS quasar spectra, we find a moderate to strong correlation between the LAE overdensity δ LAE and the effective optical depth τ LoS in lines of sight, with P value = 0.09% or <0.01% when the field containing a significant quasar overdensity is included or excluded. Cross-correlation analysis also clearly suggests that up to 4 ± 1 pMpc, LAEs tend to cluster in regions rich in H i gas, as indicated by the high τ LoS , and avoid the low τ LoS regions where the H i gas is deficient. By averaging the τ LoS as a function of the projected distance ( d ) to LAEs, we find a 30% excess signal at 2 σ level at d < 200 pkpc, indicating the dense H i in the circumgalactic medium, and a tentative excess at 400 < d < 600 pkpc in the IGM regime, corroborating the cross-correlation signal detected at about 0.5 pMpc. These statistical analyses suggest that galaxy−IGM H i correlations exist on scales ranging from several hundred pkpc to several pMpc at z ∼ 2.2.

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