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The survey of Lyman α emitters (LAEs) with the Subaru Hyper Suprime-Cam, called SILVERRUSH (Ouchi et al. 2018, PASJ, 70, S13), is producing massive data of LAEs at z ≳ 6. Here we present LAE simulations to compare the SILVERRUSH data. In 162³ comoving Mpc³ boxes, where numerical radiative transfer calculations of reionization were performed, LAEs have been modeled with physically motivated analytic recipes as a function of halo mass. We have examined 2³ models depending on the presence or absence of dispersion of halo Lyα emissivity, dispersion of the halo Lyα optical depth, τα, and halo mass dependence of τα. The unique free parameter in our model, a pivot value of τα, is calibrated so as to reproduce the z = 5.7 Lyα luminosity function (LF) of SILVERRUSH. We compare our model predictions with Lyα LFs at z = 6.6 and 7.3, LAE angular auto-correlation functions (ACFs) at z = 5.7 and 6.6, and LAE fractions in Lyman break galaxies at 5 < z < 7. The Lyα LFs and ACFs are reproduced by multiple models, but the LAE fraction turns out to be the most critical test. The dispersion of τα and the halo mass dependence of τα are essential to explain all observations reasonably. Therefore, a simple model of one-to-one correspondence between halo mass and Lyα luminosity with a constant Lyα escape fraction has been ruled out. Based on our best model, we present a formula to estimate the intergalactic neutral hydrogen fraction, xHI, from the observed Lyα luminosity density at z ≳ 6. We finally obtain xHI = 0.5-0.3+0.1 as a volume-average at z = 7.3. [ABSTRACT FROM AUTHOR]

We present an unprecedentedly large catalog consisting of 2230 ≳ L* Lyα emitters (LAEs) at z = 5.7 and 6.6 on the 13.8 and 21.2deg2 sky, respectively, that are identified by the SILVERRUSH program with the first narrow-band imaging data of the Hyper Suprime-Cam (HSC) survey. We confirm that the LAE catalog is reliable on the basis of 96 LAEs whose spectroscopic redshifts are already determined by this program and previous studies. This catalogue is also available online. Based on this catalogue, we derive the rest-frame Lyα equivalent-width distributions of LAEs at z ≃ 5.7~6.6 that are reasonably explained by the exponential profiles with scale lengths of ≃ 120~170Å, showing no significant evolution from z ≃ 5.7 to z ≃ 6.6. We find that 275 LAEs with large equivalent widths (LEWs) of >240Å are candidates of young metal poor galaxies and AGNs. We also find that the fraction of LEW LAEs to all LAEs is 4% and 21% at z ≃ 5.7 and z ~ 6.6, respectively. Our LAE catalog includes 11 Lyα blobs (LABs) that are LAEs with spatially extended Lyα emission with a profile that is clearly distinguished from those of stellar objects at the ≳3σ level. The number density of the LABs at z = 6~7 is ~10~7~10~6Mpc~3, being ~10~100 times lower than those claimed for LABs at z ≃ 2~3, suggestive of disappearing LABs at z ≳ 6, albeit with the different selection methods and criteria for the low and high-z LABs. [ABSTRACT FROM AUTHOR]

We present Lyα and UV-nebular emission line properties of bright Lyα emitters (LAEs) at z = 6-7 with a luminosity of log LLyα/[erg s-1] = 43-44 identified in the 21 deg2 area of the SILVERRUSH early sample developed with the Subaru Hyper Suprime-Cam survey data. Our optical spectroscopy newly confirms 21 bright LAEs with clear Lyα emission, and contributes to making a spectroscopic sample of 96 LAEs at z = 6-7 in SILVERRUSH. From the spectroscopic sample, we select seven remarkable LAEs as bright as Himiko and CR7 objects, and perform deep Keck/MOSFIRE and Subaru/nuMOIRCS near-infrared spectroscopy reaching the 3 σ flux limit of ~2 × 10-18 erg s-1 for the UV-nebular emission lines of He II λ1640, C IV λλ1548,1550, and O III]λλ1661,1666. Except for one tentative detection of C IV, we find no strong UV-nebular lines down to the flux limit, placing the upper limits of the rest-frame equivalent widths (EW0) of ~2-4 Å for C IV, He II, and O III] lines. We also investigate the VLT/X-SHOOTER spectrum of CR7 whose 6 σ detection of He II is claimed by Sobral et al. Although two individuals and the ESO archive service carefully reanalyzed the X-SHOOTER data that are used in the study of Sobral et al., no He II signal of CR7 is detected, supportive of weak UV-nebular lines of the bright LAEs even for CR7. The spectral properties of these bright LAEs are thus clearly different from those of faint dropouts at z ~ 7 that have strong UV-nebular lines shown in the various studies. Comparing these bright LAEs and the faint dropouts, we find anti-correlations between the UV-nebular line EW0 and the UV-continuum luminosity, which are similar to those found at z ~ 2-3. [ABSTRACT FROM AUTHOR]

We present the SILVERRUSH program strategy and clustering properties investigated with ∼2,000 Lyα emitters at z=5.7 and 6.6 found in the early data of the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey exploiting the carefully designed narrowband filters. We derive angular correlation functions with the unprecedentedly large samples of LAEs at z=6−7 over the large total area of 14−21 deg2 corresponding to 0.3−0.5 comoving Gpc2. We obtain the average large-scale bias values of bavg=4.1±0.2 (4.5±0.6) at z=5.7 (z=6.6) for ≳L∗ LAEs, indicating the weak evolution of LAE clustering from z=5.7 to 6.6. We compare the LAE clustering results with two independent theoretical models that suggest an increase of an LAE clustering signal by the patchy ionized bubbles at the epoch of reionization (EoR), and estimate the neutral hydrogen fraction to be xHI=0.15+0.15−0.15 at z=6.6. Based on the halo occupation distribution models, we find that the ≳L∗ LAEs are hosted by the dark-matter halos with the average mass of log(⟨Mh⟩/M⊙)=11.1+0.2−0.4 (10.8+0.3−0.5) at z=5.7 (6.6) with a Lyα duty cycle of 1 % or less, where the results of z=6.6 LAEs may be slightly biased, due to the increase of the clustering signal at the EoR. Our clustering analysis reveals the low-mass nature of ≳L∗ LAEs at z=6−7, and that these LAEs probably evolve into massive super-L∗ galaxies in the present-day universe. [ABSTRACT FROM AUTHOR]

We present clustering properties from 579492 Lyman-break galaxies (LBGs) at z ~ 4-6 over the 100 deg2 sky (corresponding to a 1.4 Gpc3 volume) identified in early data of the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey. We derive angular correlation functions (ACFs) for the HSC LBGs with unprecedentedly high statistical accuracies at z ~ 4-6, and compare them with the halo occupation distribution (HOD) models. We clearly identify significant ACF excesses in 10" < θ < 90", the transition scale between one- and two-halo terms, suggestive of the existence of the non-linear halo bias effect. Combining the HOD models and previous clustering measurements of faint LBGs at z ~ 4-7, we investigate the dark matter halo mass (Mh) of the z ~ 4-7 LBGs and its correlation with various physical properties including the star formation rate (SFR), the stellar-to-halo mass ratio (SHMR), and the dark matter accretion rate (M˙h) over a wide mass range of Mh/M⊙ = 4 × 1010-4 × 1012. We find that the SHMR increases from z ~ 4 to 7 by a factor of ~4 at Mh ≃ 1 × 1011M⊙ , while the SHMR shows no strong evolution in the similar redshift range at Mh ≃ 1 × 1012M⊙ . Interestingly, we identify a tight relation of SFR/M˙h-Mh showing no significant evolution beyond 0.15 dex in this wide mass range over z ~ 4-7. This weak evolution suggests that the SFR/M˙h-Mh relation is a fundamental relation in high-redshift galaxy formation whose star formation activities are regulated by the dark matter mass assembly. Assuming this fundamental relation, we calculate the cosmic star formation rate densities (SFRDs) over z = 0-10 (a.k.a. the Madau-Lilly plot). The cosmic SFRD evolution based on the fundamental relation agrees with the one obtained by observations, suggesting that the cosmic SFRD increase from z ~ 10 to 4 - 2 (decrease from z ~ 4-2 to 0) is mainly driven by the increase of the halo abundance (the decrease of the accretion rate). [ABSTRACT FROM AUTHOR]

We present average stellar population properties and dark matter halo masses of z ~ 2 Lya emitters (LAEs) from spectral energy distribution fitting and clustering analysis, respectively, using ≃ 1250 objects (NB387=25.5) in four separate fields of ≃ 1 deg2 in total. With an average stellar mass of 10.2 ± 1.8 × 108 M⊙ and star formation rate of 3.4 ± 0.4 M⊙ yr-1, the LAEs lie on an extrapolation of the star-formation main sequence (MS) to low stellar mass. Their effective dark matter halo mass is estimated to be 4.0... ×1010M⊙ with an effective bias of 1.22..., which is lower than that of z ~ 2 LAEs (1.8 ± 0.3) obtained by a previous study based on a three times smaller survey area, with a probability of 96%. However, the difference in the bias values can be explained if cosmic variance is taken into account. If such a low halo mass implies a low H I gas mass, this result appears to be consistent with the observations of a high Lya escape fraction. With the low halo masses and ongoing star formation, our LAEs have a relatively high stellar-to-halo mass ratio (SHMR) and a high efficiency of converting baryons into stars. The extended Press-Schechter formalism predicts that at z = 0 our LAEs are typically embedded in halos with masses similar to that of the Large Magellanic Cloud (LMC); they will also have similar SHMRs to the LMC, if their star formation rates are largely suppressed after z ~ 2 as some previous studies have reported for the LMC itself. [ABSTRACT FROM AUTHOR]

We have found that the dialysis of curdlan dissolved in alkaline solution into aqueous solutions of metal salts yielded multifold gel structures. Aqueous sodium chloride and potassium chloride as well as pure water induced isotropic gels. Aqueous calcium salts induced liquid crystalline gel with refractive index gradient/amorphous gel alternative structure. Aqueous salts of trivalent aluminum and ferric cations induced a rigid liquid crystalline gel, which shrank above a threshold concentration of each salt. On the other hand, Liesegang ring-like pattern was observed with aqueous solutions of mixed salts of calcium chloride and magnesium chloride. The patterns have been classified to discuss the mechanism of forming the variety of structures. [ABSTRACT FROM AUTHOR]

We report 14 and 26 protocluster candidates at z = 5.7 and 6.6 over 14 and 16 deg2 areas, respectively, selected from 2230 (259) Lyα emitters (LAEs) photometrically (spectroscopically) identified using Subaru/Hyper Suprime-Cam (HSC) deep images (Keck, Subaru, and Magellan spectra, and literature data). Six out of the 40 protocluster candidates include one to 13 spectroscopically confirmed LAEs. We conduct Monte Carlo simulations to estimate how many protocluster candidates are found by chance for randomly distributed sources, and find that the effective number of protocluster candidates at z = 5.7 (6.6) is six (five). By comparing with the cosmological Lyα radiative transfer (RT) model reproducing the LAEs with reionization effects, we find that more than half of these protocluster candidates are progenitors of present-day clusters with mass of . We then investigate the correlation between the LAE overdensity δ and the Lyα rest-frame equivalent width , because the cosmological Lyα RT model suggests that the slope of the –δ relation steepens toward the epoch of cosmic reionization (EoR), due to the existence of ionized bubbles around galaxy overdensities easing the escape of Lyα emission from the partly neutral intergalactic medium. The available HSC data suggest that the slope of the –δ correlation does not evolve from the post-reionization epoch, z = 5.7, to the EoR, z = 6.6, beyond the moderately large statistical errors. There is a possibility that we could detect the evolution of the –δ relation from z = 5.7 to 7.3 using the upcoming HSC observations that will provide large samples of LAEs at z = 6.6–7.3. [ABSTRACT FROM AUTHOR]

We detect 20 z = 7.0 Lyα emitter (LAE) candidates to L(Lyα) ∼ 2 × 1042 erg s−1 or 0.3 and in a volume of 6.1 × 105 Mpc3 in the Subaru Deep Field and the Subaru/XMM-Newton Deep Survey field by 82 hr and 37 hr of Subaru Suprime-Cam narrowband NB973 and reddest optical y-band imaging. We compare their Lyα and UV luminosity functions (LFs) and densities and Lyα equivalent widths (EWs) to those of z = 5.7, 6.6, and 7.3 LAEs from previous Suprime-Cam surveys. The Lyα LF (density) rapidly declines by a factor of ×1.5 (1.9) in L(Lyα) at z = 5.7–6.6 (160 Myr), ×1.5 (1.6) at z = 6.6–7.0 (60 Myr) at the faint end, and ×2.0 (3.8) at z = 7.0–7.3 (40 Myr). Also, in addition to the systematic decrease in EW at z = 5.7–6.6 previously found, two-thirds of the z = 7.0 LAEs detected in the UV continuum exhibit lower EWs than the z = 6.6 ones. Moreover, while the UV LF and density do not evolve at z = 5.7–6.6, they modestly decline at z = 6.6–7.0, implying galaxy evolution contributing to the decline of the Lyα LF. Comparison of the z = 7.0 Lyα LF to the one predicted by an LAE evolution model further reveals that galaxy evolution alone cannot explain all of the decline of the Lyα LF. If we attribute the discrepancy to Lyα attenuation by neutral hydrogen, the intergalactic medium transmission of Lyα photons at z = 7.0 would be . It is lower (higher) than the at z = 6.6 (7.3) derived by previous studies, suggesting rapid increase in neutral fraction at z > 6. [ABSTRACT FROM AUTHOR]

We present the Lyα luminosity functions (LFs) derived by our deep Subaru narrowband survey that identifies a total of 3137 Lyα emitters (LAEs) at z = 2.2 in five independent blank fields. This sample of LAEs is the largest to date and covers a very wide Lyα luminosity range of erg s−1. We determine the Lyα LF at z = 2.2 with unprecedented accuracy and obtain the best-fit Schechter parameters of erg s−1, Mpc−3, and , showing a steep faint-end slope. We identify a significant hump at the LF bright end ( erg s−1). Because all of the LAEs in the bright-end hump have a bright counterpart(s) in either the X-ray, UV, or radio data, this bright-end hump is not made by gravitational lensing magnification bias but by active galactic nuclei (AGNs). These AGNs allow us to derive the AGN UV LF at z ∼ 2 down to the faint magnitude limit of MUV ≃ −22.5 and to constrain the faint-end slope of the AGN UV LF, αAGN = −1.2 ± 0.1, which is flatter than those at z > 4. Based on the Lyα and UV LFs from our and previous studies, we find an increase of Lyα escape fraction from z ∼ 0 to 6 by two orders of magnitude. This large increase can be explained neither by the evolution of stellar population nor by outflow alone, but by the evolution of neutral hydrogen H i density in the interstellar medium that enhances dust attenuation for Lyα by resonance scattering. Our uniform expanding shell models suggest that the typical H i column density decreases from (z ∼ 0) to ∼1 × 1018 cm−2 (z ∼ 6) to explain the large increase. [ABSTRACT FROM AUTHOR]

We present clustering properties from 579492 Lyman-break galaxies (LBGs) at z ~ 4-6 over the 100 deg2 sky (corresponding to a 1.4 Gpc3 volume) identified in early data of the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey. We derive angular correlation functions (ACFs) for the HSC LBGs with unprecedentedly high statistical accuracies at z ~ 4-6, and compare them with the halo occupation distribution (HOD) models. We clearly identify significant ACF excesses in 10" < θ < 90", the transition scale between one- and two-halo terms, suggestive of the existence of the non-linear halo bias effect. Combining the HOD models and previous clustering measurements of faint LBGs at z ~ 4-7, we investigate the dark matter halo mass (Mh) of the z ~ 4-7 LBGs and its correlation with various physical properties including the star formation rate (SFR), the stellar-to-halo mass ratio (SHMR), and the dark matter accretion rate (M˙h) over a wide mass range of Mh/M⊙ = 4 × 1010-4 × 1012. We find that the SHMR increases from z ~ 4 to 7 by a factor of ~4 at Mh ≃ 1 × 1011M⊙ , while the SHMR shows no strong evolution in the similar redshift range at Mh ≃ 1 × 1012M⊙ . Interestingly, we identify a tight relation of SFR/M˙h-Mh showing no significant evolution beyond 0.15 dex in this wide mass range over z ~ 4-7. This weak evolution suggests that the SFR/M˙h-Mh relation is a fundamental relation in high-redshift galaxy formation whose star formation activities are regulated by the dark matter mass assembly. Assuming this fundamental relation, we calculate the cosmic star formation rate densities (SFRDs) over z = 0-10 (a.k.a. the Madau-Lilly plot). The cosmic SFRD evolution based on the fundamental relation agrees with the one obtained by observations, suggesting that the cosmic SFRD increase from z ~ 10 to 4 - 2 (decrease from z ~ 4-2 to 0) is mainly driven by the increase of the halo abundance (the decrease of the accretion rate). [ABSTRACT FROM AUTHOR]