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

Yongming Liang, Nobunari Kashikawa, Zheng Cai, Xiaohui Fan, J. Xavier Prochaska, Kazuhiro Shimasaku, Masayuki Tanaka, Hisakazu Uchiyama, Kei Ito, Rhythm Shimakawa, Kentaro Nagamine, Ikkoh Shimizu, Masafusa Onoue, Jun Toshikawa

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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 L Lyα ≈ 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 Lyα 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 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.

Original languageEnglish
Article number3
Pages (from-to)3
JournalThe Astrophysical Journal
Volume907
Issue number1
Early online date19 Jan 2021
DOIs
Publication statusPublished - 19 Jan 2021

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