MAMMOTH-Subaru. III. Lyα Halo Identified by Stacking ∼3300 Lyα Emitters at z = 2.2-2.3

In this paper, we present a Lyα halo (LAH) identified by stacking ∼3300 Lyα emitters (LAEs) at z = 2.2-2.3. We carry out imaging observations and data reduction with Subaru/Hyper Suprime-Cam. Our total survey area is ∼12 deg² and the imaging depths are 25.5-27.0 mag. Using the imaging data, we select 1240 and 2101 LAE candidates at z = 2.2 and 2.3, respectively. We carry out spectroscopic observations of our LAE candidates and data reduction with Magellan/IMACS to estimate the contamination rate of our LAE candidates. We find that the contamination rate of our sample is low (8%). We stack our LAE candidates with a median stacking method to identify the LAH at z = 2. We show that our LAH is detected until ∼100 kpc at the 2σ significance level and likely extended to ∼200 kpc at a surface brightness level of ∼10⁻²⁰ erg s⁻¹ cm⁻² arcsec⁻². Compared to those of previous studies, our LAH is brighter at radii of ∼25-100 kpc, which is not likely caused by the contamination in our sample but by the different redshifts, fields, and selection methods instead. To investigate how central galaxies affect surrounding LAHs, we divide our LAEs into subsamples based on the Lyα luminosity (L _Lyα), rest-frame Lyα equivalent width (EW₀), and UV magnitude (M _uv). We stack the subsamples and find that higher L _Lyα, smaller EW₀, and brighter M _uv cause more extended halos. Our results suggest that more massive LAEs generally have more extended LAHs.