We present results of [C II] 158 μm emission line observations, and report the spectroscopic redshift confirmation of a strongly lensed (μ ∼ 20) star-forming galaxy, MACS0308-zD1 at z = 6.2078 ± 0.0002. The [C II] emission line is detected with a signal-to-noise ratio >6 within the rest-frame UV-bright clump of the lensed galaxy (zD1.1) and exhibits multiple velocity components; the narrow [C II] has a velocity full width half maximum (FWHM) of 110 ± 20 km s−1, while broader [C II] is seen with an FWHM of 230 ± 50 km s−1. The broader [C II] component is blueshifted (−80 ± 20 km s−1) with respect to the narrow [C II] component, and has a morphology that extends beyond the UV-bright clump. We find that, while the narrow [C II] emission is most likely associated with zD1.1, the broader component is possibly associated with a physically distinct gas component from zD1.1 (e.g., outflowing or inflowing gas). Based on the nondetection of λ158μm dust continuum, we find that MACS0308-zDl's star formation activity occurs in a dust-free environment indicated by a strong upper limit of infrared luminosity ≲9 × 108 Le. Targeting this strongly lensed faint galaxy for follow-up Atacama Large Millimeter/submillimeter Array and JWST observations will be crucial to characterize the details of typical galaxy growth in the early Universe.

Abstract

We  present the demography of the dynamics and gas mass fraction of 33 extremely metal-poor galaxies (EMPGs) with metallicities of 0.015–0.195 Z _⊙ and low stellar masses of 10⁴–10⁸ M _⊙ in the local universe. We conduct deep optical integral field spectroscopy (IFS) for the low-mass EMPGs with the medium-high resolution (R = 7500) grism of the 8 m Subaru FOCAS IFU instrument by the EMPRESS 3D survey, and investigate the Hα emission of the EMPGs. Exploiting the resolution high enough for the low-mass galaxies, we derive gas dynamics with the Hα lines by the fitting of three-dimensional disk models. We obtain an average maximum rotation velocity (v _rot) of 15 ± 3 km s⁻¹ and an average intrinsic velocity dispersion (σ ₀) of 27 ± 10 km s⁻¹ for 15 spatially resolved EMPGs out of 33 EMPGs, and find that all 15 EMPGs have v _rot/σ ₀ < 1 suggesting dispersion-dominated systems. There is a clear decreasing trend of v _rot/σ ₀ with the decreasing stellar mass and metallicity. We derive the gas mass fraction (f _gas) for all 33 EMPGs, and find no clear dependence on stellar mass and metallicity. These v _rot/σ ₀ and f _gas trends should be compared with young high-z galaxies observed by the forthcoming JWST IFS programs to understand the physical origins of the EMPGs in the local universe.

The protoclusters in the epoch of reionization, traced by galaxy overdensity regions, are ideal laboratories for studying the process of stellar assembly and cosmic reionization. We present the spectroscopic confirmation of the core of the most distant protocluster at z = 7.88, A2744-z7p9OD, with the James Webb Space Telescope NIRSpec integral field unit spectroscopy. The core region includes as many as four galaxies detected in [O iii] 4960 and 5008 Å in a small area of ∼3″ × 3″, corresponding to ∼11 × 11 kpc, after the lensing magnification correction. Three member galaxies are also tentatively detected in dust continuum in Atacama Large Millimeter/submillimeter Array Band 6, which is consistent with their red ultraviolet continuum slopes, β ∼ −1.3. The member galaxies have stellar masses in the range of log(M */M ⊙) ∼7.6-9.2 and star formation rates of ∼3-50 M ⊙ yr−1, showing a diversity in their properties. FirstLight cosmological simulations reproduce the physical properties of the member galaxies including the stellar mass, [O iii] luminosity, and dust-to-stellar mass ratio, and predict that the member galaxies are on the verge of merging in a few to several tens of Myr to become a large galaxy with M * ∼ 6 × 109 M ⊙. The presence of a multiple merger and evolved galaxies in the core region of A2744-z7p9OD indicates that environmental effects are already at work 650 Myr after the Big Bang.

We report Atacama Large Millimeter/submillimeter Array Band 3 observations of CO(6−5), CO(7−6), and [C i](2−1) in B14-65666 (“Big Three Dragons”), one of the brightest Lyman-break galaxies at z > 7 in the rest-frame ultraviolet continuum, far-infrared continuum, and emission lines of [O iii] 88 μm and [C ii] 158 μm. CO(6−5), CO(7−6), and [C i](2−1), whose 3σ upper limits on the luminosities are approximately 40 times fainter than the [C ii] luminosity, are all not detected. The L [C II]/L CO(6-5) and L [C II]/L CO(7-6) ratios are higher than the typical ratios obtained in dusty star-forming galaxies or quasar host galaxies at similar redshifts, and they may suggest a lower gas density in the photodissociated region in B14-65666. By using the (1) [C ii] luminosity, (2) dust mass-to-gas mass ratio, and (3) a dynamical mass estimate, we find that the molecular gas mass (M mol) is (0.05-11) × 1010 M ⊙. This value is consistent with the upper limit inferred from the nondetection of mid-J CO and [C i](2−1). Despite the large uncertainty in M mol, we estimate a molecular gas-to-stellar mass ratio (μ gas) of 0.65-140 and a gas depletion time (τ dep) of 2.5-550 Myr; these values are broadly consistent with those of other high-redshift galaxies. B14-65666 could be an ancestor of a passive galaxy at z ≳ 4 if no gas is fueled from outside the galaxy.

We present the results of 300 pc resolution Atacama Large Millimeter/submillimeter Array imaging of the [O iii] 88 & mu;m line and dust continuum emission from a z = 8.312 Lyman-break galaxy MACS0416_Y1. The velocity-integrated [O iii] emission has three peaks that are likely associated with three young stellar clumps of MACS0416_Y1, while the channel map shows a complicated velocity structure with little indication of a global velocity gradient unlike what was found in [C ii] 158 & mu;m at a larger scale, suggesting random bulk motion of ionized gas clouds inside the galaxy. In contrast, dust emission appears as two individual clumps apparently separating or bridging the [O iii]/stellar clumps. The cross-correlation coefficient between dust and ultraviolet-related emission (i.e., [O iii] and ultraviolet continuum) is unity on a galactic scale, while it drops at <1 kpc, suggesting well-mixed geometry of multiphase interstellar media on subkiloparsec scales. If the cutoff scale characterizes different stages of star formation, the cutoff scale can be explained by gravitational instability of turbulent gas. We also report on a kiloparsec-scale off-center cavity embedded in the dust continuum image. This could be a superbubble producing galactic-scale outflows, since the energy injection from the 4 Myr starburst suggested by a spectral energy distribution analysis is large enough to push the surrounding media creating a kiloparsec-scale cavity.

Abstract

We present kinematics of six local extremely metal-poor galaxies (EMPGs) with low metallicities (0.016–0.098 Z_⊙) and low stellar masses (10^4.7–10^7.6M_⊙). Taking deep medium/high-resolution (R ∼ 7500) integral-field spectra with 8.2 m Subaru, we resolve the small inner velocity gradients and dispersions of the EMPGs with Hα emission. Carefully masking out substructures originating by inflow and/or outflow, we fit three-dimensional disk models to the observed Hα flux, velocity, and velocity dispersion maps. All the EMPGs show rotational velocities (v_rot) of 5–23 km s⁻¹ smaller than the velocity dispersions (σ₀) of 17–31 km s⁻¹, indicating dispersion-dominated (v_rot/σ₀ = 0.29–0.80 &lt; 1) systems affected by inflow and/or outflow. Except for two EMPGs with large uncertainties, we find that the EMPGs have very large gas-mass fractions of f_gas ≃ 0.9–1.0. Comparing our results with other Hα kinematics studies, we find that v_rot/σ₀ decreases and f_gas increases with decreasing metallicity, decreasing stellar mass, and increasing specific star formation rate. We also find that simulated high-z (z ∼ 7) forming galaxies have gas fractions and dynamics similar to the observed EMPGs. Our EMPG observations and the simulations suggest that primordial galaxies are gas-rich dispersion-dominated systems, which would be identified by the forthcoming James Webb Space Telescope observations at z ∼ 7.

ABSTRACT

Radio-loud active galactic nuclei (RLAGNs) are rare among AGN populations. Lacking high-resolution and high-frequency observations, their structure and evolution stages are not well understood at high redshifts. In this work, we report Atacama Large Millimeter/submillimeter Array 237 GHz continuum observation at 0.023 arcsec resolution and Very Large Array (VLA) 44 GHz continuum observation at 0.08 arcsec resolution of the radio continuum emission from a high-redshift radio and hyper-luminous infrared galaxy at z = 1.92. The new observations confirm the South-East (SE) and North-West (NW) hotspots identified by previous low-resolution VLA observations at 4.7 and 8.2 GHz and identify a radio core undetected in all previous observations. The SE hotspot has a higher flux density than the NW one does by a factor of 6, suggesting that there can be a Doppler boosting effect in the SE one. In this scenario, we estimate the advance speed of the jet head, ranging from ∼0.1c to 0.3c, which yields a mildly relativistic case. The projected linear distance between the two hotspots is ∼13 kpc, yielding a linear size (≤20 kpc) of a compact-steep-spectrum (CSS) source. Combined with new high-frequency (νobs ≥ 44 GHz) and archived low-frequency observations (νobs ≤ 8.2 GHz), we find that injection spectra of both NW and SE hotspots can be fitted with a continuous injection (CI) model. Based on the CI model, the synchrotron ages of NW and SE hotspots have an order of 105 yr, consistent with the order of magnitude 103–105 yr observed in CSS sources associated with radio AGNs at an early evolution stage. The CI model also favours the scenario in which the double hotspots have experienced a quiescent phase, suggesting that this RLAGN may have transient or intermittent activities.

We present integral field, far-infrared (FIR) spectroscopy of Mrk 54, a local Lyman continuum emitter, obtained with FIFI-LS on the Stratospheric Observatory for Infrared Astronomy. This is only the second time, after Haro 11, that [C ii] 158 mu m and [O iii] 88 mu m spectroscopy of the known LCEs have been obtained. We find that Mrk 54 has a strong [C ii] emission that accounts for similar to 1% of the total FIR luminosity, whereas it has only moderate [O iii] emission, resulting in the low [O iii]/[C ii] luminosity ratio of 0.22 +/- 0.06. In order to investigate whether [O iii]/[C ii] is a useful tracer of f (esc) (LyC escape fraction), we examine the correlations of [O iii]/[C ii] and (i) the optical line ratio of O-32 equivalent to [O iii] 5007 angstrom/[O ii] 3727 angstrom, (ii) specific star formation rate, (iii) [O iii] 88 mu m/[O i] 63 mu m ratio, (iv) gas-phase metallicity, and (v) dust temperature based on a combined sample of Mrk 54 and the literature data from the Herschel Dwarf Galaxy Survey and the LITTLE THINGS Survey. We find that galaxies with high [O iii]/[C ii] luminosity ratios could be the result of high ionization (traced by O-32), bursty star formation, high ionized-to-neutral gas volume filling factors (traced by [O iii] 88 mu m/[O i] 63 mu m), and low gas-phase metallicities, which is in agreement with theoretical predictions. We present an empirical relation between the [O iii]/[C ii] ratio and f (esc) based on the combination of the [O iii]/[C ii] and O-32 correlation, and the known relation between O-32 and f (esc). The relation implies that high-redshift galaxies with high [O iii]/[C ii] ratios revealed by the Atacama Large Millimeter/submillimeter Array may have f (esc) greater than or similar to 0.1, significantly contributing to the cosmic reionization.

Abstract

The primordial He abundance Y_P is a powerful probe of cosmology. Currently, Y_P is best determined by observations of metal-poor galaxies, while there are only a few known local extremely metal-poor (&lt;0.1Z_⊙) galaxies (EMPGs) having reliable He/H measurements with He iλ10830 near-infrared (NIR) emission. Here we present deep Subaru NIR spectroscopy for 10 EMPGs. Combining the existing optical data, He/H values of 5 out of the 10 EMPGs are reliably derived by the Markov chain Monte Carlo algorithm. Adding the existing 3 EMPGs and 51 moderately metal-poor (0.1–0.4Z_⊙) galaxies with reliable He/H estimates, we obtain ${Y}_{ { \rm{P } } }={0.2370}_{-0.0034}^{+0.0033}$ by linear regression in the (He/H) − (O/H) plane, where we increase the number of EMPGs from three to eight anchoring He/H of the most metal-poor gas in galaxies. Although our Y_P measurement and previous measurements are consistent, our result is slightly (∼1σ) smaller due to our EMPGs. Including the existing primordial deuterium D_P measurement, we constrain the effective number of neutrino species N_eff and the baryon-to-photon ratio η showing ≳1–2σ tensions with the Standard Model and Planck Collaboration et al. (2020). Motivated by the tensions, we allow the degeneracy parameter of the electron neutrino ξ_e, as well as N_eff and η, to vary. We obtain ${\xi }_{e}={0.05}_{-0.02}^{+0.03}$, ${N}_{\mathrm{eff } }={3.11}_{-0.31}^{+0.34}$, and $\eta \times {10}^{10}={6.08}_{-0.06}^{+0.06}$ from the Y_P and D_P measurements with a prior of η taken from Planck Collaboration et al. Our constraints suggest a lepton asymmetry and allow for a high value of N_eff within the 1σ level, which could mitigate the Hubble tension.

Abstract

We present our new Atacama Large Millimeter/submillimeter Array (ALMA) observations targeting CO(6–5) emission from three luminous Lyman-break galaxies (LBGs) at z_spec = 6.0293–6.2037 found in the Subaru/Hyper Suprime-Cam survey, whose [O iii] 88 μm and [C ii] 158 μm emissions have been detected with ALMA. We find a marginal detection of the CO(6–5) line from one of our LBGs, J0235–0532, at the ≃4σ significance level and obtain upper limits for the other two LBGs, J1211–0118 and J0217–0208. Our z = 6 luminous LBGs are consistent with the previously found correlation between the CO luminosity and the infrared luminosity. The unique ensemble of the multiple far-infrared emission lines and underlying continuum fed to a photodissociation region model reveals that J0235–0532 has a relatively high density of hydrogen nuclei n_H that is comparable to those of low-z (U)LIRGs, quasars, and Galactic star-forming regions with high n_H values, while the other two LBGs have lower n_H consistent with local star-forming galaxies. By carefully taking account of various uncertainties, we obtain constraints on total gas mass and gas surface density from their CO luminosity measurements. We find that J0235–0532 is located below the Kennicutt–Schmidt (KS) relation, comparable to the z = 5.7 LBG, HZ10, previously detected with CO(2–1). Combined with previous results for dusty starbursts at similar redshifts, the KS relation at z = 5–6 is on average consistent with the local one.

Abstract

We present optical-line gas metallicity diagnostics established by the combination of local SDSS galaxies and the largest compilation of extremely metal-poor galaxies (EMPGs) including new EMPGs identified by the Subaru EMPRESS survey. A total of 103 EMPGs are included, covering a large parameter space of magnitude (M_i = −19 to −7) and Hβ equivalent width (10–600 Å), i.e., wide ranges of stellar mass and star formation rate. Using reliable metallicity measurements from the direct method for these galaxies, we derive the relationships between strong optical-line ratios and gas-phase metallicity over the range of $12+\mathrm{log}({\rm{O } }/{\rm{H } })$ ≃ 6.9–8.9, corresponding to 0.02–2 solar metallicity Z_⊙. We confirm that the R23 index, ([O iii]+[O ii])/Hβ, is the most accurate metallicity indicator with a metallicity uncertainty of 0.14 dex over the range among various popular metallicity indicators. The other metallicity indicators show large scatters in the metal-poor range (≲0.1 Z_⊙). It is explained by our CLOUDY photoionization modeling that, unlike the R23 index, the other metallicity indicators do not use a sum of singly and doubly ionized lines and cannot trace both low- and high-ionization gas. We find that the accuracy of the metallicity indicators is significantly improved if one uses Hβ equivalent width measurements that tightly correlate with ionization states. In this work, we also present the relation of physical properties with the UV-continuum slope β and ionization production rate ξ_ion derived with GALEX data for the EMPGs and provide local anchors of galaxy properties together with the optical-line metallicity indicators that are available in the form of a machine-readable table and useful for forthcoming JWST spectroscopic studies.

Abstract

We present photoionization modeling of galaxy populations at z ∼ 0, 2, and &gt;6 to bridge optical and far-infrared (FIR) emission-line diagrams. We collect galaxies with measurements of optical and/or FIR ([O iii] 88 μm and [C ii] 158 μm) emission-line fluxes and plot them on the [O iii]λ5007/Hβ–[N ii]λ6585/Hα (BPT) and L([O iii]₈₈)/SFR–L([C ii]₁₅₈)/SFR diagrams, where SFR is the star formation rate and L([O iii]₈₈) and L([C ii]₁₅₈) are the FIR line luminosities. We aim to explain the galaxy distributions on the two diagrams with photoionization models that employ three nebular parameters: the ionization parameter U, hydrogen density n_H, and gaseous metallicity Z_gas. Our models successfully reproduce the nebular parameters of local galaxies, and then predict the distributions of the z ∼ 0, 2, and &gt;6 galaxies in the diagrams. The predicted distributions illustrate the redshift evolution on all the diagrams; e.g., [O iii]/Hβ and [O iii]₈₈/[C ii]₁₅₈ ratios continuously decrease from z &gt; 6 to 0. Specifically, the z &gt; 6 galaxies exhibit ∼0.5 dex higher U than low-redshift galaxies at a given Z_gas and show predicted flat distributions on the BPT diagram at ${\rm{log } }[{\rm{O } }\,{\rm\small{III } }]/{\rm{H } }\beta \,=\,$ 0.5–0.8. We find that some of the z &gt; 6 galaxies exhibit high L([O iii]₈₈)/SFR ratios. To explain these high ratios, our photoionization models require a low stellar-to-gaseous-metallicity ratio or bursty/increasing star formation history at z &gt; 6. JWST will test the predictions and scenarios for the z &gt; 6 galaxies proposed by our photoionization modeling.

We present new observations with the Atacama Large Millimeter/submillimeter Array for a gravitationally lensed galaxy at z = 9.1, MACS1149-JD1. [O iii] 88 μm emission is detected at 10σ with a spatial resolution of 1/40.3 kpc in the source plane, enabling the most distant morphokinematic study of a galaxy. The [O iii] emission is distributed smoothly without any resolved clumps and shows a clear velocity gradient with "V obs/2σ tot = 0.84 ± 0.23, where "V obs is the observed maximum velocity difference and σ tot is the velocity dispersion measured in the spatially integrated line profile, suggesting a rotating system. Assuming a geometrically thin self-gravitating rotation disk model, we obtain Vrot/σV=0.67-0.26+0.73, where V rot and σ V are the rotation velocity and velocity dispersion, respectively, still consistent with rotation. The resulting disk mass of 0.65-0.40+1.37×109 M ⊙ is consistent with being associated with the stellar mass identified with a 300 Myr old stellar population independently indicated by a Balmer break in the spectral energy distribution. We conclude that the most of the dynamical mass is associated with the previously identified mature stellar population that formed at z ∼15.

The James Webb Space Telescope (JWST) will open a new window into the most distant universe and unveil the early growth of supermassive black holes (BHs) in the first galaxies. In preparation for deep JWST imaging surveys, it is crucial to understand the color selection of high-redshift accreting seed BHs. We model the spectral energy distribution of super-Eddington accreting BHs with millions of solar masses in metal-poor galaxies at z ≳ 8, applying postprocess line transfer calculations to radiation hydrodynamical simulation results. Exposures of 10 ks with the NIRCam and MIRI broadband filters are sufficient to detect the radiation flux from the seed BHs with bolometric luminosities of L bol ≃ 1045 erg s-1. While the continuum colors are similar to those of typical low-z quasars, strong Hα line emission with a rest-frame equivalent width EWrest ≃ 1300 Å is so prominent that the line flux affects the broadband colors significantly. The unique colors, for instance, F356W - F560W 3 1 at 7 < z < 8 and F444W - F770W 3 1 at 9 < z < 12, provide robust criteria for photometric selection of rapidly growing seed BHs. Moreover, NIRSpec observations of low-ionization emission lines can test whether the BH is fed via a dense accretion disk at super-Eddington rates.

<jats:title>Abstract</jats:title>
<jats:p>We conduct intensity mapping to probe for extended diffuse Ly<jats:italic>α</jats:italic> emission around Ly<jats:italic>α</jats:italic> emitters (LAEs) at <jats:italic>z</jats:italic> ∼2−7, exploiting very deep (∼26 mag at 5<jats:italic>σ</jats:italic>) and large-area (∼4.5 deg<jats:sup>2</jats:sup>) Subaru/Hyper Suprime-Cam narrowband (NB) images and large LAE catalogs consisting of a total of 1540 LAEs at <jats:italic>z</jats:italic> = 2.2, 3.3, 5.7, and 6.6 obtained by the HSC-SSP and CHORUS projects. We calculate the spatial correlations of these LAEs with ∼1–2 billion pixel flux values of the NB images, deriving the average Ly<jats:italic>α</jats:italic> surface brightness (SB<jats:sub>Ly<jats:italic>α</jats:italic>
</jats:sub>) radial profiles around the LAEs. By carefully estimating systematics such as fluctuations of sky background and point-spread functions, we detect Ly<jats:italic>α</jats:italic> emission at 100–1000 comoving kpc around <jats:italic>z</jats:italic> = 3.3 and 5.7 LAEs at the 3.2<jats:italic>σ</jats:italic> and 3.7<jats:italic>σ</jats:italic> levels, respectively, and tentatively (=2.0<jats:italic>σ</jats:italic>) at <jats:italic>z</jats:italic> = 6.6. The emission is as diffuse as ∼10<jats:sup>−20</jats:sup>–10<jats:sup>−19</jats:sup> erg s<jats:sup>−1</jats:sup> cm<jats:sup>−2</jats:sup> arcsec<jats:sup>−2</jats:sup> and extended beyond the virial radius of a dark matter halo with a mass of 10<jats:sup>11</jats:sup>
<jats:italic>M</jats:italic>
<jats:sub>⊙</jats:sub>. While the observed SB<jats:sub>Ly<jats:italic>α</jats:italic>
</jats:sub> profiles have similar amplitudes at <jats:italic>z</jats:italic> = 2.2–6.6 within the uncertainties, the intrinsic SB<jats:sub>Ly<jats:italic>α</jats:italic>
</jats:sub> 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<jats:italic>α</jats:italic> emission around an LAE is powered by resonantly scattered Ly<jats:italic>α</jats:italic> photons in the CGM and IGM that originate from the inner part of the LAE and/or neighboring galaxies around the LAE.</jats:p>

Abstract

We present two bright galaxy candidates at z ∼ 12–13 identified in our H-dropout Lyman break selection with 2.3 deg² near-infrared deep imaging data. These galaxy candidates, selected after careful screening of foreground interlopers, have spectral energy distributions showing a sharp discontinuity around 1.7 μm, a flat continuum at 2–5 μm, and nondetections at &lt;1.2 μm in the available photometric data sets, all of which are consistent with a z &gt; 12 galaxy. An ALMA program targeting one of the candidates shows a tentative 4σ [O iii] 88 μm line at z = 13.27, in agreement with its photometric redshift estimate. The number density of the z ∼ 12–13 candidates is comparable to that of bright z ∼ 10 galaxies and is consistent with a recently proposed double-power-law luminosity function rather than the Schechter function, indicating little evolution in the abundance of bright galaxies from z ∼ 4 to 13. Comparisons with theoretical models show that the models cannot reproduce the bright end of rest-frame ultraviolet luminosity functions at z ∼ 10–13. Combined with recent studies reporting similarly bright galaxies at z ∼ 9–11 and mature stellar populations at z ∼ 6–9, our results indicate the existence of a number of star-forming galaxies at z &gt; 10, which will be detected with upcoming space missions such as the James Webb Space Telescope, Nancy Grace Roman Space Telescope, and GREX-PLUS.

Abstract

We present Keck/LRIS follow-up spectroscopy for 13 photometric candidates of extremely metal-poor galaxies (EMPGs) selected by a machine-learning technique applied to the deep (∼26 AB mag) optical and wide-area (∼500 deg²) Subaru imaging data in the EMPRESS survey. Nine out of the 13 candidates are EMPGs with an oxygen abundance (O/H) less than ∼10% solar value (O/H)_⊙, and four sources are contaminants of moderately metal-rich galaxies or no emission-line objects. Notably, two out of the nine EMPGs have extremely low stellar masses and oxygen abundances of 5 × 10⁴–7 × 10⁵M_⊙ and 2%–3% (O/H)_⊙, respectively. With a sample of five EMPGs with (Fe/O) measurements, two (three) of which are taken from this study (the literature), we confirm that two EMPGs with the lowest (O/H) ratios of ∼2% (O/H)_⊙ show high (Fe/O) ratios of ∼0.1, close to the solar abundance ratio. Comparing galaxy chemical enrichment models, we find that the two EMPGs cannot be explained by a scenario of metal-poor gas accretion/episodic star formation history due to their low (N/O) ratios. We conclude that the two EMPGs can be reproduced by the inclusion of bright hypernovae and/or hypothetical pair-instability supernovae (SNe) preferentially produced in a metal-poor environment. This conclusion implies that primordial galaxies at z ∼ 10 could have a high abundance of Fe that did not originate from Type Ia SNe with delays and that Fe may not serve as a cosmic clock for primordial galaxies.

<title>Abstract</title>
We present new Atacama Large Millimeter/submillimeter Array Band 7 observational results of a Lyman-break galaxy at <italic>z</italic> = 7.15, B14-65666 (“Big Three Dragons”), which is an object detected in [O <sc>iii</sc>] 88 <italic>μ</italic>m, [C <sc>ii</sc>] 158 <italic>μ</italic>m, and dust continuum emission during the epoch of reionization. Our targets are the [N <sc>ii</sc>] 122 <italic>μ</italic>m fine-structure emission line and the underlying 120 <italic>μ</italic>m dust continuum. The dust continuum is detected with a ∼19<italic>σ</italic> significance. From far-infrared spectral energy distribution sampled at 90, 120, and 160 <italic>μ</italic>m, we obtain a best-fit dust temperature of 40 K (79 K) and an infrared luminosity of <inline-formula>
<tex-math>
<?CDATA ${\mathrm{log } }_{10}({L}_{\mathrm{IR } }/{L}_{\odot })=11.6$?>
</tex-math>
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<mml:mrow>
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</mml:mrow>
<mml:mrow>
<mml:mn>10</mml:mn>
</mml:mrow>
</mml:msub>
<mml:mo stretchy="false">(</mml:mo>
<mml:msub>
<mml:mrow>
<mml:mi>L</mml:mi>
</mml:mrow>
<mml:mrow>
<mml:mi>IR</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mrow>
<mml:mo stretchy="true">/</mml:mo>
</mml:mrow>
<mml:msub>
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<mml:mi>L</mml:mi>
</mml:mrow>
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<mml:mo>⊙</mml:mo>
</mml:mrow>
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<mml:mo stretchy="false">)</mml:mo>
<mml:mo>=</mml:mo>
<mml:mn>11.6</mml:mn>
</mml:math>
<inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2a36ieqn1.gif" xlink:type="simple" />
</inline-formula> (12.1) at the emissivity index <italic>β</italic> = 2.0 (1.0). The [N <sc>ii</sc>] 122 <italic>μ</italic>m line is not detected. The 3<italic>σ</italic> upper limit of the [N <sc>ii</sc>] luminosity is 8.1 × 10⁷
<italic>L</italic>
_⊙. From the [N <sc>ii</sc>], [O <sc>iii</sc>], and [C <sc>ii</sc>] line luminosities, we use the Cloudy photoionization code to estimate nebular parameters as functions of metallicity. If the metallicity of the galaxy is high (<italic>Z</italic> &gt; 0.4 <italic>Z</italic>
_⊙), the ionization parameter and hydrogen density are <inline-formula>
<tex-math>
<?CDATA ${\mathrm{log } }_{10}U\simeq -2.7\pm 0.1$?>
</tex-math>
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
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<mml:mn>10</mml:mn>
</mml:mrow>
</mml:msub>
<mml:mi>U</mml:mi>
<mml:mo>≃</mml:mo>
<mml:mo>−</mml:mo>
<mml:mn>2.7</mml:mn>
<mml:mo>±</mml:mo>
<mml:mn>0.1</mml:mn>
</mml:math>
<inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2a36ieqn2.gif" xlink:type="simple" />
</inline-formula> and <italic>n</italic>
_H ≃ 50–250 cm⁻³, respectively, which are comparable to those measured in low-redshift galaxies. The nitrogen-to-oxygen abundance ratio, N/O, is constrained to be subsolar. At <italic>Z</italic> &lt; 0.4 <italic>Z</italic>
_⊙, the allowed <italic>U</italic> drastically increases as the assumed metallicity decreases. For high ionization parameters, the N/O constraint becomes weak. Finally, our Cloudy models predict the location of B14-65666 on the BPT diagram, thereby allowing a comparison with low-redshift galaxies.

We present an IGM H i tomographic map in a survey volume of 16 × 19 × 131 h-3 commoving Mpc3 (cMpc3) centered at MAMMOTH-1 nebula and three neighboring quasars at z = 2.3. The MAMMOTH-1 nebula is an enormous Lyα nebula (ELAN), hosted by a type-II quasar dubbed MAMMOTH1-QSO, that extends over 1 h-1 cMpc with no clear physical origin. Here we investigate the H i-gas distribution around MAMMOTH1-QSO with the ELAN and three neighboring type-I quasars, making the IGM H i tomographic map with a spatial resolution of 2.6 h -1 cMpc. Our H i tomographic map is reconstructed with H i Lyα forest absorption of bright background objects at z = 2.4-2.9: one eBOSS quasar and 16 Keck/LRIS galaxy spectra. We estimate the radial profile of H i overdensity for MAMMOTH1-QSO, and find that MAMMOTH1-QSO resides in a volume with fairly weak H i absorption. This suggests that MAMMOTH1-QSO may have a proximity zone where quasar illuminates and photoionizes the surrounding H i gas and suppresses H i absorption, and that the ELAN is probably a photoionized cloud embedded in the cosmic web. The H i radial profile of MAMMOTH1-QSO is very similar to those of three neighboring type-I quasars at z = 2.3, which is compatible with the AGN unification model. We compare the distributions of the H i absorption and star-forming galaxies in our survey volume, and identify a spatial offset between density peaks of star-forming galaxies and H i gas. This segregation may suggest anisotropic UV background radiation created by star-forming galaxy density fluctuations.

We search for galaxies with a strong Balmer break (Balmer break galaxies; BBGs) at z 6 over a 0.41 deg2 effective area in the COSMOS field. Based on rich imaging data, including data obtained with the Atacama Large Millimeter/submillimeter Array (ALMA), three candidates are identified by their extremely red K [3.6] colors, as well as by nondetection in the X-ray, optical, far-infrared, and radio bands. The nondetection in the deep ALMA observations suggests that they are not dusty galaxies but BBGs at z 6, although contamination from active galactic nuclei at z 0 cannot be completely ruled out for the moment. Our spectral energy distribution analyses reveal that the BBG candidates at z 6 have stellar masses of x 101 M, dominated by old stellar populations with ages of > 700 Myr. Assuming that all three candidates are real BBGs at z 6, we estimate the stellar mass density to be 2.411 x 104 M. Mpc-3. This is consistent with an extrapolation from the lower-redshift measurements. The onset of star formation in the three BBG candidates is expected to be several hundred million yr before the observed epoch of z 6. We estimate the star formation rate density (SI-RD) contributed by progenitors of the BBGs to be 2.4-12 x 10-5 Mc, yr-1 Mpc3 at z > 14 (99.7% confidence range). Our result suggests a smooth evolution of the SFRD beyond z = 8.

We present a velocity of galactic outflows in star-forming galaxies at the highest redshift, z ∼ 6, so far studied with metal absorption lines. Absorption-line studies of galactic outflows need well-determined redshifts, but there are few strong emission lines in the observed-frame optical spectra of galaxies at high redshifts. In this work, we use the systemic redshifts determined by the ALMA [CII]158 μm emission lines. The sample consists of seven Lyman break galaxies at 5.1 &lt
z &lt
5.7 whose Keck/DEIMOS and ALMA data are available in the archive. The outflow maximum velocity (νmax) is estimated by a fitting of line profiles to metal absorption lines in a composite spectrum. We find that νmax monotonically increases from z ∼ 0 to 6 and that νmax tightly correlates with the halo circular velocity estimated from the stellar mass.

Hyper Suprime-Cam (HSC) is a wide-field imaging camera on the prime focus of the 8.2-m Subaru telescope on the summit of Mauna Kea in Hawaii. A team of scientists from Japan, Taiwan, and Princeton University is using HSC to carry out a 300-night multi-band imaging survey of the high-latitude sky. The survey includes three layers: the Wide layer will cover 1400 deg2 in five broad bands (grizy), with a 5 σ point-source depth of r ≈ 26. The Deep layer covers a total of 26 deg2 in four fields, going roughly a magnitude fainter, while the UltraDeep layer goes almost a magnitude fainter still in two pointings of HSC (a total of 3.5 deg2). Here we describe the instrument, the science goals of the survey, and the survey strategy and data processing. This paper serves as an introduction to a special issue of the Publications of the Astronomical Society of Japan, which includes a large number of technical and scientific papers describing results from the early phases of this survey.

The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) is a three-layered imaging survey aimed at addressing some of the most important outstanding questions in astronomy today, including the nature of dark matter and dark energy. The survey has been awarded 300 nights of observing time at the Subaru Telescope, and it started in 2014 March. This paper presents the first public data release of HSC-SSP. This release includes data taken in the first 1.7yr of observations (61.5 nights), and each of the Wide, Deep, and UltraDeep layers covers about 108, 26, and 4 square degrees down to depths of i ∼ 26.4, ∼26.5, and ∼27.0mag, respectively (5a for point sources). All the layers are observed in five broad bands (grizy), and the Deep and UltraDeep layers are observed in narrow bands as well. We achieve an impressive image quality of 0".6 in the i band in the Wide layer. We show that we achieve 1%-2% point spread function (PSF) photometry (root mean square) both internally and externally (against Pan-STARRS1), and ∼10mas and 40 mas internal and external astrometric accuracy, respectively. Both the calibrated images and catalogs are made available to the community through dedicated user interfaces and database servers. In addition to the pipeline products, we also provide value-added products such as photometric redshifts and a collection of public spectroscopic redshifts. Detailed descriptions of all the data can be found online.

We conduct a systematic study of galactic outflows in star-forming galaxies at z ∼ 0-2 based on the absorption lines of optical spectra taken from SDSS DR7, DEEP2 DR4, and Keck (Erb et al.). We carefully make stacked spectra of homogeneous galaxy samples with similar stellar mass distributions at z ∼ 0-2 and perform the multicomponent fitting of model absorption lines and stellar continua to the stacked spectra. We obtain the maximum (vmax) and central (vout) outflow velocities and estimate the mass loading factors (η), a ratio of the mass outflow rate to the star formation rate (SFR). Investigating the redshift evolution of the outflow velocities measured with the absorption lines whose depths and ionization energies are similar (Na I D and Mg I at z ∼ 0-1
Mg II and C II at z ∼ 1-2), we identify, for the first time, that the average value of vmax (vout) significantly increases by 0.05-0.3 dex from z ∼ 0 to 2 at a given SFR. Moreover, we find that the value of η increases from z ∼ 0 to 2 by η ∝ (1 + z)1.2±0.3 at a given halo circular velocity vcir, albeit with a potential systematics caused by model parameter choices. The redshift evolution of vmax (vout) and η is consistent with the galaxy-size evolution and the local velocity-SFR surface density relation and explained by high gas fractions in high-redshift massive galaxies, which is supported by recent radio observations. We obtain a scaling relation of η ∝ νcira for a = -0.2 ± 1.1 in our z ∼ 0 galaxies that agrees with the momentum-driven outflow model (a = -1) within the uncertainties.

We conduct a systematic search for galaxies at z = 0.1 1.5-with [O II]λ3727, [O III]λ5007, or Hal6563 emission lines extended over at least 30 kpc by using deep narrowband and broadband imaging in the-Subaru-XMM Deep Survey field. These extended emission-line galaxies are dubbed [O II], [O III], or Ha blobs. Based on a new selection method that securely selects-extended emission-line galaxies, we find 77 blobs at z = 0.40 1.46-with the isophotal area of emission lines down to 1.2 × 10-18 erg s-1 cm-2 kpc-2. Four of them are spectroscopically confirmed to be [O III] blobs at z=0.83. We identify AGN activities in eight blobs with X-ray and radio data, and find that the fraction of AGN contribution increases with increasing isophotal area of the extended emission. With the Kolmogorov-Smirnov (KS) and Anderson-Darling tests, we confirm that the stellar-mass distributions of Ha and [O II] blobs are not drawn from those of the emitters at the &gt
90% confidence level in that Ha and [O II] blobs are located at the massive end of the distributions, but cannot reject anull hypothesis of being the same distributions in terms of the specific star formation rates. It is suggested that galactic-scale outflows tend to be more prominent in more massive star-forming galaxies. Exploiting our sample homogeneously selected over the large area, we derive the number densities of blobs at each epoch. The number densities of blobs decrease drastically with redshifts at a rate that is larger than that of the decrease of cosmic star formation densities.