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![Combined spectrum of z = 6.96 galaxy, IOK-1.The bottom panel shows the removed OH sky emission lines. An echelle grism (175 lines per millimetre, resolution 1,600) with z' filter and 0.8" slit was used to obtain 11 spectra of 30-min exposure each, dithered along the slit by 1". The Lyman- emission peak is located at 9,682 Å. This feature was confirmed to follow the dithered shifts along the slit. The Lyman- emission has a total flux of 2.0 10-17erg s-1 cm-2, consistent with the estimate from the NB973 image (2.7 10-17erg s-1 cm-2), and a full width at half-maximum of 13 Å. The Lyman- luminosity is LLy = 1.1 1043 erg s-1, corresponding to SFRLy = 10 M yr-1. The emission feature is significant at the 5.5 level. The asymmetric emission line profile matches the composite template line profile (dashed line) produced from 12 Lyman- emitters at z = 6.6 (ref. 22) normalized and shifted to z = 6.96. This emission cannot be unresolved z = 1.6 [O ii] doublet lines with 7.0 Å separation (3,726 Å, 3,729 Å at rest frame), as finer sky lines (about 5.1–6.2 Å) are clearly resolved. Similarly, the line is not H, [O iii] 4,959 Å, [O iii] 5,007 Å, H, [S ii] 6,717 Å or [S ii] 6,731 Å, because our spectrum shows none of the other lines that should accompany any of these lines in the observed wavelength range. The possibility that OH lines mask other lines was carefully examined for each case and ruled out. There appears to be an extremely weak emission at around z = 7.02 in the 3 h integration spectrum of IOK-2, but this needs further integration for confirmation.](profile/Yuichi-Matsuda/publication/6818976/figure/fig2/AS:271199485820928@1441670404017/Combined-spectrum-of-z-696-galaxy-IOK-1The-bottom-panel-shows-the-removed-OH-sky.png)
Combined spectrum of z = 6.96 galaxy, IOK-1.The bottom panel shows the removed OH sky emission lines. An echelle grism (175 lines per millimetre, resolution 1,600) with z' filter and 0.8" slit was used to obtain 11 spectra of 30-min exposure each, dithered along the slit by 1". The Lyman- emission peak is located at 9,682 Å. This feature was confirmed to follow the dithered shifts along the slit. The Lyman- emission has a total flux of 2.0 10-17erg s-1 cm-2, consistent with the estimate from the NB973 image (2.7 10-17erg s-1 cm-2), and a full width at half-maximum of 13 Å. The Lyman- luminosity is LLy = 1.1 1043 erg s-1, corresponding to SFRLy = 10 M yr-1. The emission feature is significant at the 5.5 level. The asymmetric emission line profile matches the composite template line profile (dashed line) produced from 12 Lyman- emitters at z = 6.6 (ref. 22) normalized and shifted to z = 6.96. This emission cannot be unresolved z = 1.6 [O ii] doublet lines with 7.0 Å separation (3,726 Å, 3,729 Å at rest frame), as finer sky lines (about 5.1–6.2 Å) are clearly resolved. Similarly, the line is not H, [O iii] 4,959 Å, [O iii] 5,007 Å, H, [S ii] 6,717 Å or [S ii] 6,731 Å, because our spectrum shows none of the other lines that should accompany any of these lines in the observed wavelength range. The possibility that OH lines mask other lines was carefully examined for each case and ruled out. There appears to be an extremely weak emission at around z = 7.02 in the 3 h integration spectrum of IOK-2, but this needs further integration for confirmation.
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When galaxy formation started in the history of the Universe remains unclear. Studies of the cosmic microwave background indicate that the Universe, after initial cooling (following the Big Bang), was reheated and reionized by hot stars in newborn galaxies at a redshift in the range 6 < z < 14 (ref. 1). Though several candidate galaxies at redshift...
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Citations
... The continuum properties were derived from a fit to the photometry. Note that SDF-63544 is also known as IOK-1 (e.g., Iye et al. 2006). Additional Keck observations resulted in three detections of Lyα with the spectrographs LRIS and NIRSPEC (Schenker et al. 2012). ...
The rest-frame UV recombination emission line Ly-alpha can be powered by ionizing photons from young massive stars in star forming galaxies, but its ability to be resonantly scattered by neutral gas complicates its interpretation. For reionization era galaxies, a neutral intergalactic medium (IGM) will scatter Ly-alpha from the line of sight, making Ly-alpha a useful probe of the neutral fraction at z>6. Here, we explore Ly-alpha in JWST/NIRSpec spectra from the ongoing GTO program JADES, which targets hundreds of galaxies in the well-studied GOODS-S and GOODS-N fields. These sources are UV-faint (-20.4<MUV<-16.4), and thus represent a poorly-explored class of galaxies. The low spectral resolution (R~100) spectra of a subset of 93 galaxies in GOODS-S with z_spec>5.5 (as derived with optical lines) are fit with line and continuum models, in order to search for significant line emission. Through exploration of the R100 data, we find evidence for Ly-alpha in 15 sources. Additional analysis of the R1000 data from the same set of galaxies results in five additional detections. This sample allows us to place observational constraints on the fraction of galaxies with Ly-alpha emission in the redshift range 5.5<z<7.5, with a decrease from z=6 to z=7. We also find a positive correlation between Ly-alpha equivalent width and MUV, as seen in other samples. These results are used to estimate the neutral gas fraction at z~7, agreeing with previous results (XHI~0.5-0.9).
... LAE LF studies have reached various constraints for reionization. Some report suppression of the LAE LF in ranges within 5.7 < z < 7, with inferred neutral fractions on the order of 20%-40% (Iye et al. 2006;Kashikawa et al. 2006;McQuinn et al. 2007;Ouchi et al. 2010;Kashikawa et al. 2011;Konno et al. 2014Konno et al. , 2018. Others report upper bounds on neutral IGM (Malhotra & Rhoads 2004, 2006, including some bounds that are tight enough to challenge some of the suggested detections of neutral gas , whose results of <20%-30% at z = 7 are consistent with a fully ionized medium). ...
We use large simulations of Ly α emitters with different fractions of ionized intergalactic medium to quantify the clustering of Ly α emitters as measured by the void probability function (VPF), and how it evolves under different ionization scenarios. We quantify how well we might be able to distinguish between these scenarios with a deep spectroscopic survey using the future Nancy Grace Roman Space Telescope. Because Roman will be able to carry out blind spectroscopic surveys of Ly α emitters continuously between 7 < z < 12 to sensitivities of at least 10 ⁻¹⁷ erg s ⁻¹ over a wide field of view, it can measure the epoch of reionization as well as the pace of ionization of the intergalactic medium (IGM). We compare deep Roman surveys covering roughly 1, 4, and 16 deg ² , and quantify what constraints on reionization the VPF may find for these surveys. A survey of 1 deg ² would distinguish between very late reionization and early reionization to 3 σ near z = 7.7 with the VPF. The VPF of a 4 deg ² survey can distinguish between slow versus fast, as well as early versus late, reionization at >3 σ –4 σ at several redshifts between 7 < z < 9. However, a survey of 13–16 deg ² would allow the VPF to give several robust constraints (>5–8 σ ) across the epoch of reionization, and would yield a detailed history of the reionization of the IGM and its effect on Ly α emitter clustering.
... LAE LF studies have reached various constraints for reionization. Some report suppression of the LAE LF in ranges within 5.7 < z < 7, with inferred neutral fractions of order 20-40 percent (McQuinn et al. 2007;Kashikawa et al. 2006;Iye et al. 2006;Ouchi et al. 2010;Kashikawa et al. 2011;Konno et al. 2014Konno et al. , 2018. Others report upper bounds on neutral IGM (Malhotra & Rhoads 2004, 2006, including some bounds that are tight enough to challenge some of the suggested detections of neutral gas whose results of < 20-30 percent at z = 7 are consistent with a fully ionized medium]Wold2022a. ...
We use large simulations of Lyman-Alpha Emitters with different fractions of ionized intergalactic medium to quantify the clustering of Ly$\alpha$ emitters as measured by the Void Probability function (VPF), and how it evolves under different ionization scenarios. We quantify how well we might be able to distinguish between these scenarios with a deep spectroscopic survey using the future Nancy Grace Roman Space Telescope. Since Roman will be able to carry out blind spectroscopic surveys of Ly$\alpha$ emitters continuously between $7<z<12$ to sensitivities of at least $10^{-17}$ erg sec$^{-1}$ over a wide field of view, it can measure the epoch of reionization as well as the pace of ionization of the intergalactic medium (IGM). We compare deep Roman surveys covering roughly 1, 4, and 16 deg$^2$, and quantify what constraints on reionization the VPF may find for these surveys. A survey of 1 deg$^2$ would distinguish between very late reionization and early reionization to 3$\sigma$ near $z=7.7$ with the VPF. The VPF of a 4 deg$^2$ survey can distinguish between slow vs.\ fast, and early vs.\ late, reionization at $> 3-4\sigma$ at several redshifts between $7<z<9$. However, a survey of 13-16 deg$^2$ would allow the VPF to give several robust constraints ($>5-8\sigma$) across the epoch of reionization, and would yield a detailed history of the reionization of the IGM and its effect on Lyman-$\alpha$ Emitter clustering.
... LAE candidates are usually selected in ground-based narrowband imaging surveys, and follow-up spectroscopy is sometimes taken to confirm them. This narrowband technique has been widely used to search for high-z LAEs at z ≈ 5.7, 6.6, and 7.0 (e.g., Hu et al. 2002;Kodaira et al. 2003;Rhoads et al. 2004;Taniguchi et al. 2005;Iye et al. 2006;Kashikawa et al. 2006Kashikawa et al. , 2011Hu et al. 2010;Rhoads et al. 2012;Jiang et al. 2017;Zheng et al. 2017;Shibuya et al. 2018). Some LAEs (or candidates) at z > 7 have also been reported using this technique (e.g., Tilvi et al. 2010;Shibuya et al. 2012). ...
We present a sample of Ly α emitters (LAEs) at z ≈ 6.6 from our spectroscopic survey of high-redshift galaxies using the multi-object spectrograph M2FS on the Magellan Clay telescope. The sample consists of 36 LAEs selected by the narrowband (NB921) technique over nearly 2 deg ² in the sky. These galaxies generally have high Ly α luminosities spanning a range of ∼3 × 10 ⁴² –7 × 10 ⁴³ erg s ⁻¹ , and include some of the most Ly α -luminous galaxies known at this redshift. They show a positive correlation between the Ly α line width and Ly α luminosity, similar to the relation previously found in z ≈ 5.7 LAEs. Based on the spectroscopic sample, we calculate a sophisticated sample completeness correction and derive the Ly α luminosity function (LF) at z ≈ 6.6. We detect a density bump at the bright end of the Ly α LF that is significantly above the best-fit Schechter function, suggesting that very luminous galaxies tend to reside in overdense regions that have formed large ionized bubbles around them. By comparing with the z ≈ 5.7 Ly α LF, we confirm that there is a rapid LF evolution at the faint end, but a lack of evolution at the bright end. The fraction of the neutral hydrogen in the intergalactic medium at z ≈ 6.6 estimated from such an evolution is about 0.3 ± 0.1, supporting a rapid and rather late process of cosmic reionization.
... LAE candidates are usually selected in groundbased narrowband imaging surveys, and follow-up spectroscopy is sometimes taken to confirm them. This narrowband technique has been widely used to search for high-redshift LAEs at z ≈ 5.7, 6.6, and 7.0 (e.g., Hu et al. 2002;Kodaira et al. 2003;Rhoads et al. 2004;Taniguchi et al. 2005;Iye et al. 2006;Kashikawa et al. 2006Kashikawa et al. , 2011Hu et al. 2010;Rhoads et al. 2012;Jiang et al. 2017;Zheng et al. 2017;Shibuya et al. 2018). Some LAEs (or candidates) at z > 7 have also been reported using this technique (e.g., Tilvi et al. 2010;Shibuya et al. 2012). ...
We present a sample of Ly{\alpha} emitters (LAEs) at $z\approx6.6$ from our spectroscopic survey of high-redshift galaxies using the multi-object spectrograph M2FS on the Magellan Clay telescope. The sample consists of 36 LAEs selected by the narrow-band (NB921) technique over nearly 2 deg$^2$ in the sky. These galaxies generally have high Ly{\alpha} luminosities spanning a range of ${\sim}3\times10^{42}{-}7\times10^{43}$ erg s$^{-1}$, and include some of the most Ly{\alpha}-luminous galaxies known at this redshift. They show a positive correlation between the Ly{\alpha} line width and Ly{\alpha} luminosity, similar to the relation previously found in $z\approx5.7$ LAEs. Based on the spectroscopic sample, we calculate a sophisticated sample completeness correction and derive the Ly{\alpha} luminosity function (LF) at $z\approx6.6$. We detect a density bump at the bright end of the Ly{\alpha} LF that is significantly above the best-fit Schechter function, suggesting that very luminous galaxies tend to reside in overdense regions that have formed large ionized bubbles around them. By comparing with the $z\approx5.7$ Ly{\alpha} LF, we confirm that there is a rapid LF evolution at the faint end, but a lack of evolution at the bright end. The fraction of the neutral hydrogen in the intergalactic medium at $z\approx6.6$ estimated from such a rapid evolution is about $\sim0.3\pm0.1$, supporting a rapid and rather late process of cosmic reionization.
... Indeed, although HST eventually discovered a galaxy at z = 11.1, it was not definitively confirmed until seven years after the most recent servicing mission. The redshift record was held by a z < 7 source (Iye et al. 2006(Iye et al. ) until 2009. Finding these highredshift galaxies required not only a technical improvement in our ability to observe them, but also new search techniques, both in the design of multiwavelength surveys targeting the high-redshift universe (Grogin et al. 2011;Koekemoer et al. 2011, etc.) and the novel technique of using gravitational lensing from massive clusters to exceed the typical HST detection threshold (Lotz et al. 2017;Steinhardt et al. 2020). ...
One of the primary goals for the upcoming James Webb Space Telescope is to observe the first galaxies. Predictions for planned and proposed surveys have typically focused on average galaxy counts, assuming a random distribution of galaxies across the observed field. The first and most-massive galaxies, however, are expected to be tightly clustered, an effect known as cosmic variance. We show that cosmic variance is likely to be the dominant contribution to uncertainty for high-redshift mass and luminosity functions, and that median high-redshift and high-mass galaxy counts for planned observations lie significantly below average counts. Several different strategies are considered for improving our understanding of the first galaxies, including adding depth, area, and independent pointings. Adding independent pointings is shown to be the most efficient both for discovering the single highest-redshift galaxy and also for constraining mass and luminosity functions.
... Indeed, although HST eventually discovered a galaxy at z = 11.1, it was not definitively confirmed until seven years after the most recent servicing mission. The redshift record was held by a z < 7 source (Iye et al. 2006(Iye et al. ) until 2009. Finding these high-redshift galaxies required not only a technical improvement in our ability to observe them, but also new search techniques, both in the design of multi-wavelength surveys targeting the high-redshift Universe (Grogin et al. 2011;Koekemoer et al. 2011, etc.) and the novel technique of using gravitational lensing from massive clusters to exceed the typical HST detection threshold (Lotz et al. 2017;Steinhardt et al. 2020). ...
One of the primary goals for the upcoming James Webb Space Telescope (JWST) is to observe the first galaxies. Predictions for planned and proposed surveys have typically focused on average galaxy counts, assuming a random distribution of galaxies across the observed field. The first and most massive galaxies, however, are expected to be tightly clustered, an effect known as cosmic variance. We show that cosmic variance is likely to be the dominant contribution to uncertainty for high-redshift mass and luminosity functions, and that median high-redshift and high-mass galaxy counts for planned observations lie significantly below average counts. Several different strategies are considered for improving our understanding of the first galaxies, including adding depth, area, and independent pointings. Adding independent pointings is shown to be the most efficient both for discovering the single highest-redshift galaxy and also for constraining mass and luminosity functions.
... The author of this paper and his group made an additional survey at z F 7.0 using NB973 and reported finding a single source, IOK-1, at z F 6.964, that remained the most distant galaxy spectroscopically confirmed until 2011. 111) Figure 29 compares the distribution of Lyman , emitters at three epochs: z F 5.7, 6.6, and 7.0. An abrupt drop in the number density between redshifts 6.6 and 7.0 as is shown in Fig. 29 indicates that the transparency of the intergalactic medium against Lyman , photons changed during this period. ...
... The most distant galaxies. The Lyman , emitter IOK-1 at z F 6.964111) remained the highest redshift galaxy during 2006.9-2010.12. In 2010, all of the top 10 entries of the most distant galaxies spectroscopically confirmed were monopolized by Subaru Telescope discoveries. ...
... The distribution of Lyman , emitters, as confirmed in the SDF at three epochs, z F 5.7, 109) 6.6, 110) and 7.0,111) with limiting narrow-band magnitudes of 26.0, 26.0 and 24.9, respectively. Although the sensitivity for detection is 1.1magnitude more shallow for z F 7.0, the clear drop in the number of Lyman , emitters indicates cosmic reionization proceeding significantly at 6.6 5 z 5 7.0.Fig. ...
The Subaru Telescopea⁾ is an 8.2 m optical/infrared telescope constructed during 1991–1999 and has been operational since 2000 on the summit area of Maunakea, Hawaii, by the National Astronomical Observatory of Japan (NAOJ). This paper reviews the history, key engineering issues, and selected scientific achievements of the Subaru Telescope. The active optics for a thin primary mirror was the design backbone of the telescope to deliver a high-imaging performance. Adaptive optics with a laser-facility to generate an artificial guide-star improved the telescope vision to its diffraction limit by cancelling any atmospheric turbulence effect in real time. Various observational instruments, especially the wide-field camera, have enabled unique observational studies. Selected scientific topics include studies on cosmic reionization, weak/strong gravitational lensing, cosmological parameters, primordial black holes, the dynamical/chemical evolution/interactions of galaxies, neutron star mergers, supernovae, exoplanets, proto-planetary disks, and outliers of the solar system. The last described are operational statistics, plans and a note concerning the culture-and-science issues in Hawaii.
... The author of this paper and his group made an additional survey at z = 7.0 using NB973 and reported finding a single source, IOK-1, at z = 6.964, that remained the most distant galaxy spectroscopically confirmed until 2011 (111). Figure 29 compares the distribution of Lyman α emitters at three epochs: z =5.7, 6.6, and 7.0. ...
The Subaru Telescope is an 8.2 m optical/infrared telescope constructed during 1991--1999 and has been operational since 2000 on the summit area of Maunakea, Hawaii, by the National Astronomical Observatory of Japan (NAOJ). This paper reviews the history, key engineering issues, and selected scientific achievements of the Subaru Telescope. The active optics for a thin primary mirror was the design backbone of the telescope to deliver a high-imaging performance. Adaptive optics with a laser-facility to generate an artificial guide-star improved the telescope vision to its diffraction limit by cancelling any atmospheric turbulence effect in real time. Various observational instruments, especially the wide-field camera, have enabled unique observational studies. Selected scientific topics include studies on cosmic reionization, weak/strong gravitational lensing, cosmological parameters, primordial black holes, the dynamical/chemical evolution/interactions of galaxies, neutron star mergers, supernovae, exoplanets, proto-planetary disks, and outliers of the solar system. The last described are operational statistics, plans and a note concerning the culture-and-science issues in Hawaii.
... Studies of galaxy formation, evolution, and cosmology necessarily require that we investigate the high redshift Universe. The class of systems known as Lyman Alpha Emitters (LAEs, Partridge & Peebles 1967) is particularly helpful to build samples of galaxies in the distant redshift greater than two, with a few samples also in the redshift range z ∼ 6 − 9 (Hu et al. 2002;Kodaira et al. 2003;Iye et al. 2006;Willis et al. 2006;Ouchi et al. 2008;Ono et al. 2010). In recent times several large spectroscopic or photometric surveys have been developed with the explicit aim of specifically targeting LAEs, such as the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX, Hill et al. 2008a) and its Pilot Survey , the Large-Area Lyman Alpha survey (LALA, Rhoads et al. 2000;Malhotra & Rhoads 2002), the Multiwavelength Survey by Yale-Chile (MUSYC, Gawiser et al. 2006a), the Subaru Deep Survey, and Subaru/XMM-Newton Deep Survey (SXDS, Ouchi et al. 2003Ouchi et al. , 2008. ...
Ly$\alpha$-emitting galaxies (LAEs) are easily detectable in the high-redshift Universe and are potentially efficient tracers of large scale structure at early epochs, as long as their observed properties do not strongly depend on environment. We investigate the luminosity and equivalent width functions of LAEs in the overdense field of a protocluster at redshift $z \simeq 3.78$. Using a large sample of LAEs (many spectroscopically confirmed), we find that the Ly$\alpha$ luminosity distribution is well-represented by a Schechter (1976) function with $\log(L^{\ast}/{\rm erg s^{-1}}) = 43.26^{+0.20}_{-0.22}$ and $\log(\phi^{\ast}/{\rm Mpc^{-3}})=-3.40^{+0.03}_{-0.04}$ with $\alpha=-1.5$. Fitting the equivalent width distribution as an exponential, we find a scale factor of $\omega=79^{+15}_{-15}\: \mathring{A}$. We also measured the Ly$\alpha$ luminosity and equivalent width functions using the subset of LAEs lying within the densest cores of the protocluster, finding similar values for $L^*$ and $\omega$. Hence, despite having a mean overdensity more than 2$\times$ that of the general field, the shape of the Ly$\alpha$ luminosity function and equivalent width distributions in the protocluster region are comparable to those measured in the field LAE population by other studies at similar redshift. While the observed Ly$\alpha$ luminosities and equivalent widths show correlations with the UV continuum luminosity in this LAE sample, we find that these are likely due to selection biases and are consistent with no intrinsic correlations within the sample. This protocluster sample supports the strong evolutionary trend observed in the Ly$\alpha$ escape fraction and suggest that lower redshift LAEs are on average significantly more dusty that their counterparts at higher redshift.
