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Register a new userSILVERRUSH. V. Census of Lya, [OIII]5007, Ha, and [CII]158um Line Emission with ~1000 LAEs at z=4.9-7.0 Revealed with Subaru/HSC
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We investigate Lya, [OIII]5007, Ha, and [CII]158um emission from 1124 galaxies at z=4.9-7.0. Our sample is composed of 1092 Lya emitters (LAEs) at z=4.9, 5.7, 6.6, and 7.0 identified by Subaru/Hyper Suprime-Cam (HSC) narrowband surveys covered by Spitzer large area survey with Subaru/HSC (SPLASH) and 34 galaxies at z=5.148-7.508 with deep ALMA [CII]158um data in the literature. Fluxes of strong rest-frame optical lines of [OIII] and Ha (Hb) are constrained by significant excesses found in the SPLASH 3.6 and 4.5um photometry. At z=4.9, we find that the rest-frame Ha equivalent width and the Lya escape fraction f_Lya positively correlate with the rest-frame Lya equivalent width EW^0_Lya. The f_Lya-EW^0_Lya correlation is similarly found at z~0-2, suggesting no evolution of the correlation over z~0-5. The typical ionizing photon production efficiency of LAEs is logxi_ion/[Hz erg^-1]~25.5 significantly (60-100%) higher than those of LBGs at a given UV magnitude. At z=5.7-7.0, there exists an interesting turn-over trend that the [OIII]/Ha flux ratio increases in EW^0_Lya~0-30 A, and then decreases out to EW^0_Lya~130 A. We also identify an anti-correlation between a [CII] luminosity to star-formation rate ratio (L_[CII]/SFR) and EW^0_Lya at the >99% confidence level. We carefully investigate physical origins of the correlations with stellar-synthesis and photoionization models, and find that a simple anti-correlation between EW_Lya^0 and metallicity explains self-consistently all of the correlations of Lya, Ha, [OIII]/Ha, and [CII] identified in our study, indicating detections of metal-poor (~0.03 Zo) galaxies with EW^0_Lya~200 A.
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We conduct intensity mapping to probe for extended diffuse Ly$alpha$ emission around Ly$alpha$ emitters (LAEs) at $zsim2-7$, exploiting very deep ($sim26$ mag at $5sigma$) and large-area ($sim4.5$ deg$^2$) Subaru/Hyper Suprime-Cam narrow-band (NB) images and large LAE catalogs consisting of a total of 1781 LAEs at $z=2.2$, $3.3$, $5.7$, and $6.6$ obtained by the HSC-SSP SILVERRUSH and CHORUS projects. We calculate the spatial correlations of these LAEs with $sim1-2$ billion pixel flux values of the NB images, deriving the average Ly$alpha$ surface brightness (${rm SB_{Lyalpha}}$) radial profiles around the LAEs. By carefully estimating systematics such as fluctuations of sky background and point spread functions, we detect diffuse Ly$alpha$ emission ($sim10^{-20}-10^{-19}$ erg s$^{-1}$ cm$^{-2}$ arcsec$^{-2}$) at $100-1000$ comoving kpc around $z=3.3$ LAEs at the $4.1sigma$ level and tentatively ($sim2sigma$) at the other redshifts, beyond the virial radius of a dark-matter halo with a mass of $10^{11} M_odot$. While the observed ${rm SB_{Lyalpha}}$ profiles have similar amplitudes at $z=2.2-6.6$ within the uncertainties, the intrinsic ${rm SB_{Lyalpha}}$ profiles (corrected for the cosmological dimming effect) increase toward high redshifts. This trend may be explained by increasing hydrogen gas density due to the evolution of the cosmic volume. Comparisons with theoretical models suggest that extended Ly$alpha$ emission around a LAE is powered by resonantly scattered Ly$alpha$ photons in the CGM and IGM that originates from the inner part of the LAE, and/or neighboring galaxies around the LAE.
We present a new catalog of $9318$ Ly$alpha$ emitter (LAE) candidates at $z = 2.2$, $3.3$, $4.9$, $5.7$, $6.6$, and $7.0$ that are photometrically selected by the SILVERRUSH program with a machine learning technique from large area (up to $25.0$ deg$^2$) imaging data with six narrowband filters taken by the Subaru Strategic Program with Hyper Suprime-Cam (HSC SSP) and a Subaru intensive program, Cosmic HydrOgen Reionization Unveiled with Subaru (CHORUS). We construct a convolutional neural network that distinguishes between real LAEs and contaminants with a completeness of $94$% and a contamination rate of $1$%, enabling us to efficiently remove contaminants from the photometrically selected LAE candidates. We confirm that our LAE catalogs include $177$ LAEs that have been spectroscopically identified in our SILVERRUSH programs and previous studies, ensuring the validity of our machine learning selection. In addition, we find that the object-matching rates between our LAE catalogs and our previous results are $simeq 80$-$100$% at bright NB magnitudes of $lesssim 24$ mag. We also confirm that the surface number densities of our LAE candidates are consistent with previous results. Our LAE catalogs will be made public on our project webpage.
We present the SILVERRUSH program strategy and clustering properties investigated with $sim 2,000$ Ly$alpha$ 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 $14-21$ deg$^2$ corresponding to $0.3-0.5$ comoving Gpc$^2$. We obtain the average large-scale bias values of $b_{rm avg}=4.1pm 0.2$ ($4.5pm 0.6$) at $z=5.7$ ($z=6.6$) for $gtrsim L^*$ 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 $x_{rm HI}=0.15^{+0.15}_{-0.15}$ at $z=6.6$. Based on the halo occupation distribution models, we find that the $gtrsim L^*$ LAEs are hosted by the dark-matter halos with the average mass of $log (left < M_{rm h} right >/M_odot) =11.1^{+0.2}_{-0.4}$ ($10.8^{+0.3}_{-0.5}$) at $z=5.7$ ($6.6$) with a Ly$alpha$ 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 $gtrsim L^*$ LAEs at $z=6-7$, and that these LAEs probably evolve into massive super-$L^*$ galaxies in the present-day universe.
We report the Subaru Hyper Suprime-Cam (HSC) discovery of two Ly$alpha$ blobs (LABs), dubbed z70-1 and z49-1 at $z=6.965$ and $z=4.888$ respectively, that are Ly$alpha$ emitters with a bright ($log L_{rm Lyalpha}/{rm [erg s^{-1}]}>43.4$) and spatially-extended Ly$alpha$ emission, and present the photometric and spectroscopic properties of a total of seven LABs; the two new LABs and five previously-known LABs at $z=5.7-6.6$. The z70-1 LAB shows the extended Ly$alpha$ emission with a scale length of $1.4pm 0.2$ kpc, about three times larger than the UV continuum emission, making z70-1 the most distant LAB identified to date. All of the 7 LABs, except z49-1, exhibit no AGN signatures such as X-ray emission, {sc Nv}$lambda$1240 emission, or Ly$alpha$ line broadening, while z49-1 has a strong {sc Civ}$lambda$1548 emission line indicating an AGN on the basis of the UV-line ratio diagnostics. We carefully model the point-spread functions of the HSC images, and conduct two-component exponential profile fitting to the extended Ly$alpha$ emission of the LABs. The Ly$alpha$ scale lengths of the core (star-forming region) and the halo components are $r_{rm c}=0.6-1.2$ kpc and $r_{rm h}=2.0-13.8$ kpc, respectively. The average $r_{rm h}$ of the LABs falls on the extrapolation of the $r_{rm h}$-Ly$alpha$ luminosity relation of the Ly$alpha$ halos around VLT/MUSE star-forming galaxies at the similar redshifts, suggesting that typical LABs at $zgtrsim5$ are not special objects, but star-forming galaxies at the bright end.
We perform SED fitting analysis on a COSMOS sample covering UV-to-FIR wavelengths with emission lines from the FMOS survey. The sample of 182 objects with H$alpha$ and [OIII]$lambda5007$ emission spans over a range of $1.40<rm{z}<1.68$. We obtain robust estimates of stellar mass ($10^{9.5}-10^{11.5}~rm{M_odot}$) and SFR ($10^1-10^3~rm{M_odot}~rm{yr}^{-1}$) from the Bayesian analysis with CIGALE fitting continuum photometry and H$alpha$. We obtain a median attenuation of A$_rm{Halpha}=1.16pm0.19$ mag and A$_rm{[OIII]}=1.41pm0.22$ mag. H$alpha$ and [OIII]$lambda5007$ attenuations are found to increase with stellar mass, confirming previous findings. A difference of $57$% in the attenuation experienced by emission lines and continuum is found in agreement with the lines being more attenuated than the continuum. New CLOUDY HII-region models in CIGALE enable good fits of H$alpha$, H$beta$, [OIII]$lambda5007$ emission lines with differences smaller than $0.2$ dex. Fitting [NII]$lambda6584$ line is challenging due to well-known discrepancies in the locus of galaxies in the BPT diagram at intermediate redshifts. We find a positive correlation for SFR and dust-corrected L$_rm{[OIII]lambda5007}$ and we derive the linear relation $log_{10}rm{(SFR/rm{M}_odot~rm{yr}^{-1})}=log_{10} (rm{L}_{[rm{OIII]}}/rm{ergs~s^{-1}})-(41.20pm0.02)$. Leaving the slope as a free parameter leads to $log_{10}rm{(SFR/rm{M}_odot~rm{yr}^{-1})}=(0.83pm0.06)log_{10}(rm{L}_{[rm{OIII]}}/rm{ergs~s^{-1}})-(34.01pm2.63)$. Gas-phase metallicity and ionization parameter variations account for a $0.24$ dex and $1.1$ dex of the dispersion, respectively. An average value of $logrm{U}approx-2.85$ is measured for this sample. Including HII-region models to fit simultaneously photometry and emission line fluxes are paramount to analyze future data from surveys such as MOONS and PFS.
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