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

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 Lyα 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 Lyα emitter (LAE) candidates at z = 2.177 ± 0.023 down to the Lyα luminosity of LLyα ≈ 2 × 1042 erg s−1 to construct the galaxy overdensity maps, covering an effective area of 5.39 deg2. Combining the sample with the Lyα absorption estimated from 64 (e) BOSS quasar spectra, we find a moderate to strong correlation between the LAE overdensity δLAE and the effective optical depth τLoS 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 τLoS, and avoid the low τLoS regions where the H I gas is deficient. By averaging the τLoS as a function of the projected distance (d) to LAEs, we find a 30% excess signal at 2σ 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.