The correlation between neutral Hydrogen (HI) in the intergalactic medium (IGM) and galaxies now attracts great interests. We select four fields which include several coherently strong Ly$alpha$ absorption systems at $zsim2.2$ detected by using background quasars from the whole SDSS/(e)BOSS database. Deep narrow-band and $g$-band imaging are performed using the Hyper Suprime-Cam on the Subaru Telescope. We select out 2,642 Ly$alpha$ emitter (LAE) candidates at $z=2.177pm0.023$ down to the Ly$alpha$ luminosity of $L_{text{Ly}alpha}approx 2 times 10^{42} {rm erg~s}^{-1}$ to construct the galaxy overdensity maps, covering an effective area of 5.39 deg$^2$. Combining the sample with the Ly$alpha$ absorption estimated from 64 (e)BOSS quasar spectra, we find a moderate to strong correlation between the LAE overdensity $delta_{rm LAE}$ and the effective optical depth $tau_{rm LoS}$ in line-of-sights, with $P$-value$=0.09%$ ($<0.01%$) when the field that contains a significant quasar overdensity is in(ex)cluded. The cross-correlation analysis also clearly suggests that up to $4pm1$ pMpc, LAEs tend to cluster in the regions rich in HI gas, indicated by the high $tau_{rm LoS}$, and avoid the low $tau_{rm LoS}$ region where the HI gas is deficient. By averaging the $tau_{rm LoS}$ as a function of the projected distance ($d$) to LAEs, we find a $30%$ excess signal at $2sigma$ level at $d<200$ pkpc, indicating the dense HI in circumgalactic medium, and a tentative excess at $400<d<600$ pkpc in IGM regime, corroborating the cross-correlation signal detected at about $0.5$ pMpc. These statistical analyses indicate that galaxy$-$IGM HI correlations exist on scales ranging from several hundred pkpc to several pMpc at $zsim2.2$.
Download