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Abstract We present luminosity functions (LFs) and angular correlation functions (ACFs) derived from 18,960 Lyαemitters (LAEs) atz = 2.2−7.3 over a wide survey area of ≲24 deg²that are identified in the narrowband data of the HSC-SSP and CHORUS surveys. Confirming the large sample with 241 spectroscopically identified LAEs, we determine LyαLFs and ACFs in the brighter luminosity range down to 0.5L_⋆, and confirm that our measurements are consistent with previous studies but offer significantly reduced statistical uncertainties. The improved precision of our ACFs allows us to clearly detect one-halo terms at some redshifts, and provides large-scale bias measurements that indicate host halo masses of ∼10¹¹M_⊙overz ≃ 2−7. By comparing our LyαLF (ACF) measurements with reionization models, we estimate the neutral hydrogen fractions in the intergalactic medium to bex_Hi < 0.05 (= ${0.06}_{-0.03}^{+0.12}$) atz= 5.7 andx_Hi= $0.15_{-0.08}^{+0.10}$( ${0.21}_{-0.14}^{+0.19}$), $0.18_{-0.12}^{+0.14}$, and $0.75_{-0.13}^{+0.09}$atz= 6.6, 7.0, and 7.3, respectively. Our findings suggest that the neutral hydrogen fraction remains relatively low,x_Hi ≲ 0.2, atz = 5−7, but increases sharply atz > 7, reachingx_Hi ∼ 0.9 byz ≃ 8−9, as indicated by recent JWST studies. The combination of our results from LAE observations with recent JWST observations suggests that the major epoch of reionization occurred atz ∼ 7−8, likely driven by the emergence of massive sources emitting significant ionizing photons. 

Abstract We present UV and Ly α radial surface brightness (SB) profiles of Ly α emitters (LAEs) at z = 2.84 detected with the Hyper Suprime-Cam on the Subaru Telescope. The depth of our data, together with the wide-field coverage including a protocluster, enable us to study the dependence of Ly α halos (LAHs) on various galaxy properties, including Mpc scale environments. UV and Ly α images of 3490 LAEs are extracted, and stacking the images yields SB sensitivity of ∼ 1 × 10 − 20 erg s − 1 cm − 2 arcsec − 2 in Ly α , reaching the expected level of optically thick gas illuminated by the UV background at z ∼ 3. Fitting of the two-component exponential function gives the scale-lengths of 1.56 ± 0.01 and 10.4 ± 0.3 pkpc. Dividing the sample according to their photometric properties, we find that, while the dependence of halo scale-length on environment outside of the protocluster core is not clear, LAEs in the central regions of protoclusters appear to have very large LAHs, which could be caused by combined effects of source overlapping and diffuse Ly α emission from cool intergalactic gas permeating the forming protocluster core irradiated by active members. For the first time, we identify UV halos around bright LAEs that are probably due to a few lower-mass satellite galaxies. Through comparison with recent numerical simulations, we conclude that, while scattered Ly α photons from the host galaxies are dominant, star formation in satellites evidently contributes to LAHs, and that fluorescent Ly α emission may be boosted within protocluster cores at cosmic noon and/or near bright QSOs. 

Abstract We present near-infrared (NIR) ground-basedY,J,H, andKimaging obtained in the James Webb Space Telescope (JWST) North Ecliptic Pole Time Domain Field (NEP TDF) using the MMT-Magellan Infrared Imager and Spectrometer on the MMT. These new observations cover a field of approximately 230 arcmin²inY,H, andK,and 313 arcmin²inJ. Using Monte Carlo simulations, we estimate a 1σdepth relative to the background sky of (Y, J, H, K) = (23.80, 23.53, 23.13, 23.28) in AB magnitudes for point sources at a 95% completeness level. These observations are part of the ground-based effort to characterize this region of the sky, supplementing space-based data obtained with Chandra, NuSTAR, XMM, AstroSat, Hubble Space Telescope, and JWST. This paper describes the observations and reduction of the NIR imaging and combines these NIR data with archival imaging in the visible, obtained with the Subaru Hyper-Suprime-Cam, to produce a merged catalog of 57,501 sources. The new observations reported here, plus the corresponding multiwavelength catalog, will provide a baseline for time-domain studies of bright sources in the NEP TDF.