Sample Of Lyman Break Galaxies Research Articles

High redshift LBGs from deep broadband imaging for future spectroscopic surveys

Lyman break galaxies (LBGs) are promising probes for clustering measurements at high redshift, z > 2, a region only covered so far by Lyman-α forest measurements. In this paper, we investigate the feasibility of selecting LBGs by exploiting the existence of a strong deficit of flux shortward of the Lyman limit, due to various absorption processes along the line of sight. The target selection relies on deep imaging data from the HSC and CLAUDS surveys in the g, r, z and u bands, respectively, with median depths reaching 27 AB in all bands. The selections were validated by several dedicated spectroscopic observation campaigns with DESI. Visual inspection of spectra has enabled us to develop an automated spectroscopic typing and redshift estimation algorithm specific to LBGs. Based on these data and tools, we assess the efficiency and purity of target selections optimised for different purposes. Selections providing a wide redshift coverage retain 57% of the observed targets after spectroscopic confirmation with DESI, and provide an efficiency for LBGs of 83±3%, for a purity of the selected LBG sample of 90±2%. This would deliver a confirmed LBG density of ~ 620 deg-2 in the range 2.3 < z < 3.5 for a r-band limiting magnitude r < 24.2. Selections optimised for high redshift efficiency retain 73% of the observed targets after spectroscopic confirmation, with 89±4% efficiency for 97±2% purity. This would provide a confirmed LBG density of ~ 470 deg-2 in the range 2.8 < z < 3.5 for a r-band limiting magnitude r < 24.5. A preliminary study of the LBG sample 3d-clustering properties is also presented and used to estimate the LBG linear bias. A value of b LBG = 3.3 ± 0.2 (stat.) is obtained for a mean redshift of 2.9 and a limiting magnitude in r of 24.2, in agreement with results reported in the literature.

A novel analysis of contamination in Lyman-break galaxy samples at z ∼ 6-8: spatial correlation with intermediate-redshift galaxies at z ∼ 1.3-2

ABSTRACT Potential contamination from low/intermediate-redshift galaxies, such as objects with a prominent Balmer break, affects the photometric selection of high-redshift galaxies through identification of a Lyman break. Traditionally, contamination is estimated from spectroscopic follow-up and/or simulations. Here, we introduce a novel approach to estimating contamination for Lyman-break galaxy (LBG) samples based on measuring spatial correlation with the parent population of lower redshift interlopers. We propose two conceptual approaches applicable to different survey strategies: a single large contiguous field and a survey consisting of multiple independent lines of sight. For a large single field, we compute the cross-correlation function between galaxies at redshift $z \sim 6$ and intermediate-redshift galaxies at $z \sim 1.3$. We apply the method to the CANDELS GOODS-S and XDF surveys and compare the measurement with simulated mock observations, finding that the contamination level in both cases is not measurable and lies below 5.5 per cent (at 90 per cent confidence). For random-pointing multiple field surveys, we measure instead the number count correlation between high-redshift galaxies and interlopers, as a two-point correlation analysis is not generally feasible. We show an application to the LBG samples at redshift $z \sim 8$ and the possible interloper population at $z \sim 2$ in the Brightest of Reionizing Galaxies (BoRG) survey. By comparing the Pearson correlation coefficient with the result from Monte Carlo simulations, we estimate a contamination fraction of $62^{+13}_{-39} \, \mathrm{ per}\, \mathrm{ cent}$, consistent with previous estimates in the literature. These results validate the proposed approach and demonstrate its utility as an independent check of contamination in photometrically selected samples of high-redshift galaxies.

MIDIS: JWST NIRCam and MIRI Unveil the Stellar Population Properties of Lyα Emitters and Lyman-break Galaxies at z ≃ 3–7

We study the stellar population properties of 182 spectroscopically confirmed (MUSE/VLT) Lyα emitters (LAEs) and 450 photometrically selected Lyman-break galaxies (LBGs) at z = 2.8–6.7 in the Hubble Extreme Deep Field. Leveraging the combined power of Hubble Space Telescope and JWST NIRCam and MIRI observations, we analyze their rest-frame UV-through-near-IR spectral energy distributions, with MIRI playing a crucial role in robustly assessing the LAEs’ stellar masses and ages. Our LAEs are low-mass objects (log10(M⋆/M⊙)≃7.5) with little or no dust extinction (E(B − V) ≃ 0.1) and a blue UV continuum slope (β ≃ −2.2). While 75% of our LAEs are young (<100 Myr), the remaining 25% have significantly older stellar populations (≥100 Myr). These old LAEs are statistically more massive, less extinct, and have lower specific star formation rate than young LAEs. Besides, they populate the plane of M ⋆ versus star formation rate along the main sequence of star-forming galaxies, while young LAEs populate the starburst region. The comparison between the LAEs’ properties and those of a stellar-mass-matched sample of LBGs shows no statistical difference between these objects, except for the LBGs’ redder UV continuum slope and marginally larger E(B − V) values. Interestingly, 48% of the LBGs have ages <10 Myr and are classified as starbursts, but lack detectable Lyα emission. This is likely due to H i resonant scattering and/or dust-selective extinction. Overall, we find that JWST observations are crucial in determining the properties of LAEs and shedding light on their comparison with LBGs.

The Hα Luminosity Function of Galaxies at z ∼ 4.5

We present the Hα luminosity function (LF) derived from a large sample of Lyman break galaxies at z ∼ 4.5 over the GOODS-South and North fields. This study makes use of the new, full-depth Spitzer/IRAC [3.6] and [4.5] imaging from the GOODS Re-ionization Era wide-Area Treasury from the Spitzer program. The Hα flux is derived from the offset between the continuum flux estimated from the best-fit spectral energy distribution, and the observed photometry in IRAC [3.6]. From these measurements, we build the Hα LF and study its evolution providing the best constraints of this property at high redshift, where spectroscopy of Hα is not yet available. Schechter parameterizations of the Hα LF show a decreasing evolution of Φ∗ with redshift, increasing evolution in L ∗, and no significant evolution in the faint-end slope at high z. We find that star formation rates (SFRs) derived from Hα are higher than those derived from the rest-frame UV for low SFR galaxies but the opposite happens for the highest SFRs. This can be explained by lower mass galaxies (also lower SFR) having, on average, rising star formation histories (SFHs), while at the highest masses the SFHs may be declining. The SFR function is steeper, and because of the excess SFR(Hα) compared to SFR(UV) at low SFRs, the SFR density estimated from Hα is higher than the previous estimates based on UV luminosities.

First Identification of a CMB Lensing Signal Produced by 1.5Million Galaxies at z∼4: Constraints on Matter Density Fluctuations at High Redshift.

We report the first detection of the dark matter distribution around Lyman break galaxies (LBGs) at high redshift through the cosmic microwave background (CMB) lensing measurements with the public Planck PR3 κ map. The LBG sample consists of 1 473 106 objects with the median redshift of z∼4 that are identified in a total area of 305 deg^{2} observed by the Hyper Suprime-Cam Strategic Survey Program survey. After careful investigations of systematic uncertainties, such as contamination from foreground galaxies and cosmic infrared background, we obtain the significant detection of the CMB lensing signal at 5.1σ that is dominated by 2-halo term signals of the LBGs. Fitting a simple model consisting of the Navarro-Frenk-White profile and the linear-bias model, we obtain the typical halo mass of M_{h}=2.9_{-2.5}^{+9.5}×10^{11} h^{-1} M_{⊙}. Combining the CMB lensing and galaxy-galaxy clustering signals on the large scales, we demonstrate the first cosmological analysis at z∼4 that constrains (Ω_{m0},σ_{8}). We find that our constraint on σ_{8} is roughly consistent with the Planck cosmology, while this σ_{8} constraint is lower than the Planck cosmology over the 1σ level. This study opens up a new window for constraining cosmological parameters at high redshift by the combination of CMB and high-z galaxies, as well as studying the interplay between galaxy evolution and large-scale structure at such high redshift, by upcoming CMB and optical and near-infrared imaging surveys.

Prospects for kSZ2–Galaxy Cross-correlations during Reionization

Abstract We explore a new approach for extracting reionization-era contributions to the kinetic Sunyaev–Zel’dovich (kSZ) effect. Our method utilizes the cross-power spectrum between filtered and squared maps of the cosmic microwave background (CMB) and photometric galaxy surveys during the Epoch of Reionization (EoR). This kSZ2–galaxy cross-power spectrum statistic has been successfully detected at lower redshifts (z ≲ 1.5). Here we extend this method to z ≳ 6 as a potential means to extract signatures of patchy reionization. We model the expected signal across multiple photometric redshift bins using seminumeric simulations of the reionization process. In principle, the cross-correlation statistic robustly extracts reionization-era contributions to the kSZ signal, while its redshift evolution yields valuable information regarding the timing of reionization. Specifically, the model cross-correlation signal near ℓ ∼ 1000 peaks during the early stages of the EoR, when about 20% of the volume of the universe is ionized. Detectable ℓ modes mainly reflect squeezed-triangle configurations of the related bispectrum, quantifying correlations between the galaxy overdensity field on large scales and the smaller-scale kSZ power. We forecast the prospects for detecting this signal using future wide-field samples of Lyman-break galaxies from the Roman Space Telescope and next-generation CMB surveys including the Simons Observatory, CMB-S4, and CMB-HD. We find that a roughly 13σ detection is possible for CMB-HD and Roman after summing over all ℓ modes. We discuss the possibilities for improving this approach and related statistics, with the aim of moving beyond simple detections to measure the scale and redshift dependence of the cross-correlation signals.

CDFS-6664: A Candidate of Lyman-continuum Emission at z ∼ 3.8 Detected by the Hubble Deep UV Legacy Survey

Abstract We report the detection of Lyman continuum (LyC) emission from the galaxy, CDFS-6664, at z = 3.797 in a sample of Lyman break galaxies with detected [O iii] emission lines. The LyC emission is detected with a significance ∼5σ in the F336W band of the Hubble Deep UV Legacy Survey, corresponding to the 650–770 Å rest frame. The light centroid of the LyC emission is offset from the galaxy center by about 0.″2 (1.4 pkpc). The Hubble deep images at longer wavelengths show that the emission is unlikely provided by low-redshift interlopers. The photometric and spectroscopic data show that the possible contribution of an active galactic nucleus is quite low. Fitting the spectral energy distribution of this source to stellar population synthesis models, we find that the galaxy is young (∼50 Myr) and actively forming stars with a rate of 52.1 ± 4.9 M ⊙ yr−1. The significant star formation and the spatially offset LyC emission support a scenario where the ionizing photons escape from the low-density cavities in the ISM excavated by massive young stars. From the nebular model, we estimate the escape fraction of LyC photons to be 38% ± 7% and the corresponding intergalactic medium (IGM) transmission to be 60%, which deviates more than 3σ from the average transmission. The unusually high IGM transmission of LyC photons in CDFS-6664 may be related to a foreground type-2 quasar, CDF-202, at z = 3.7, with a projected separation of 1.′2 only. The quasar may have photoevaporated optically thick absorbers and enhance the transmission on the sightline of CDFS-6664.

The correlation of high-redshift galaxies with the thermal Sunyaev–Zel’dovich effect traces reionization

ABSTRACT We explore a potential new probe of reionization: the cross-correlation of high-redshift galaxies with maps of the thermal Sunyaev–Zel’dovich (tSZ) effect. We consider two types of high-redshift galaxies: Lyman break galaxies (LBGs) and Lyman-α emitters (LAEs). LBGs and LAEs will be detected in large numbers at high redshift (z ≈ 4–7) by ongoing and future surveys. We consider a future LBG sample from The Rubin Observatory Legacy Survey of Space and Time, and a selection of LAEs modelled after the Subaru SILVERRUSH programme, but covering a much larger sky fraction. The tSZ effect is sensitive to a line-of-sight integral of the ionized gas pressure, and is measured across large patches of sky using multifrequency cosmic microwave background (CMB) surveys. We consider forecast tSZ maps from CMB Stage 4 and more futuristic observations. Using a suite of hydrodynamical simulations, we show that LBGs and LAEs are correlated with the tSZ signal from reionization. The cross-spectra between LBGs/LAEs with tSZ maps contain information about the reionization history of the Universe, such as the distribution of bubble sizes, and could be used to directly measure the timing of reionization. The amplitude of the signal is small, however, and its detectability is hindered by low-redshift contributions to tSZ maps and by instrumental noise. If the low-redshift contribution to the observed tSZ signal is suppressed by masking of massive haloes, a combination of overlapping futuristic CMB and galaxy surveys could probe this signal.

Cosmic Reionization On Computers: The Galaxy–Halo Connection between 5 ≤ z ≤ 10

Abstract We explore the connection between the stellar component of galaxies and their host halos during the epoch of reionization (5 ≤ z ≤ 10) using the CROC (Cosmic Reionization on Computers) simulations. We compare simulated galaxies with observations and find that CROC underpredicts the abundance of luminous galaxies when compared to observed UV luminosity functions, and analogously the most massive galaxies when compared to observed stellar mass functions. We can trace the deficit of star formation to high redshifts, where the slope of the star formation rate to stellar mass relation is consistent with observations, but the normalization is systematically low. This results in a star formation rate density and stellar mass density that are systematically offset from observations. However, the less luminous or lower stellar mass objects have luminosities and stellar masses that agree fairly well with observational data. We explore the stellar-to-halo mass ratio (SHMR), a key quantity that is difficult to measure at high redshifts and that models do not consistently predict. In CROC, the SHMR decreases with redshift, a trend opposite to some abundance-matching studies. These discrepancies uncover where future effort should be focused in order to improve the fidelity of modeling cosmic reionization. We also compare the CROC galaxy bias with observational measurements using Lyman-break galaxy samples, finding reasonable consistency.

The impact of scatter in the galaxy UV luminosity to halo mass relation on Ly α visibility during the epoch of reionization

ABSTRACT The reionization of hydrogen is closely linked to the first structures in the Universe, so understanding the timeline of reionization promises to shed light on the nature of these early objects. In particular, transmission of Lyman alpha (Ly α) from galaxies through the intergalactic medium (IGM) is sensitive to neutral hydrogen in the IGM, so can be used to probe the reionization timeline. In this work, we implement an improved model of the galaxy UV luminosity to dark matter halo mass relation to infer the volume-averaged fraction of neutral hydrogen in the IGM from Ly α observations. Many models assume that UV-bright galaxies are hosted by massive dark matter haloes in overdense regions of the IGM, so reside in relatively large ionized regions. However, observations and N-body simulations indicate that scatter in the UV luminosity–halo mass relation is expected. Here, we model the scatter (though we assume the IGM topology is unaffected) and assess the impact on Ly α visibility during reionization. We show that UV luminosity–halo mass scatter reduces Ly α visibility compared to models without scatter, and that this is most significant for UV-bright galaxies. We then use our model with scatter to infer the neutral fraction, $\overline{x}_{\mathrm{ H}\,{\small I}}$, at z ∼ 7 using a sample of Lyman-break galaxies in legacy fields. We infer $\overline{x}_{\mathrm{ H}\,{\small I}} = 0.55_{-0.13}^{+0.11}$ with scatter, compared to $\overline{x}_{\mathrm{ H}\,{\small I}} = 0.59_{-0.14}^{+0.12}$ without scatter, a very slight decrease and consistent within the uncertainties. Finally, we place our results in the context of other constraints on the reionization timeline and discuss implications for future high-redshift galaxy studies.

The ALMA Frontier Fields Survey

Context. The Hubble Frontier Fields offer an exceptionally deep window into the high-redshift universe, covering a substantially larger area than the Hubble Ultra-Deep field at low magnification and probing 1–2 mag deeper in exceptional high-magnification regions. This unique parameter space, coupled with the exceptional multi-wavelength ancillary data, can facilitate for useful insights into distant galaxy populations. Aims. We aim to leverage Atacama Large Millimetre Array (ALMA) band 6 (≈263 GHz) mosaics in the central portions of five Frontier Fields to characterize the infrared (IR) properties of 1582 ultraviolet (UV)-selected Lyman-Break Galaxies (LBGs) at redshifts of z ∼ 2–8. We investigated individual and stacked fluxes and IR excess (IRX) values of the LBG sample as functions of stellar mass (M⋆), redshift, UV luminosity and slope β, and lensing magnification. Methods. LBG samples were derived from color-selection and photometric redshift estimation with Hubble Space Telescope photometry. Spectral energy distributions -templates were fit to obtain luminosities, stellar masses, and star formation rates for the LBG candidates. We obtained individual IR flux and IRX estimates, as well as stacked averages, using both ALMA images and u–v visibilities. Results. Two (2) LBG candidates were individually detected above a significance of 4.1-σ, while stacked samples of the remaining LBG candidates yielded no significant detections. We investigated our detections and upper limits in the context of the IRX–M⋆ and IRX–β relations, probing at least one dex lower in stellar mass than past studies have done. Our upper limits exclude substantial portions of parameter space and they are sufficiently deep in a handful of cases to create mild tension with the typically assumed attenuation and consensus relations. We observe a clear and smooth trend between M⋆ and β, which extends to low masses and blue (low) β values, consistent with expectations from previous works.

Dust mass and dust production efficiencies on the redshift frontier

AbstractIn order to clarify the dust production in the early Universe, we constrain the dust mass in high-redshift (z ≳ 5) galaxies using the upper limits obtained by ALMA. We perform fitting to the rest-frame UV–far-infrared spectral energy distribution (SED) of a giant Lyα emitter, Himiko, at z = 6.6 and a composite SED of z &gt; 5 Lyman break galaxies (LBGs). For Himiko, we obtain a high dust temperature &gt; 70 K. This high dust temperature puts a strong upper limit on the total dust mass Md ≲ 2 × 106 M⊙, and the dust mass produced per supernova (SN) md,SN ≲ 0.1 M⊙. Such a low md,SN suggests significant loss of dust by reverse shock destruction or outflow. For the LBG sample, we only obtain an upper limit for md,SN as ∼2 M⊙. This clarifies the importance of observing UV-bright objects (like Himiko) to constrain the dust production by SNe.

Rest-frame far-ultraviolet to far-infrared view of Lyman break galaxies at z = 3: Templates and dust attenuation

Aims. This work explores, from a statistical point of view, the rest-frame far-ultraviolet (FUV) to far-infrared (FIR) emission of a population of Lyman-break galaxies (LBGs) at z ∼ 3 that cannot be individually detected from current FIR observations. Methods. We performed a stacking analysis over a sample of ∼17 000 LBGs at redshift 2.5 &lt; z &lt; 3.5 in the COSMOS field. The sample is binned as a function of UV luminosity (LFUV), UV continuum slope (βUV), and stellar mass (M*), and then stacked at optical (BVriz bands), near-infrared (YJHKs bands), IRAC (3.6, 4.5, 5.6, and 8.0 μm), MIPS (24 μm), PACS (100 and 160 μm), SPIRE (250, 350, and 500 μm), and AzTEC (1.1 mm) observations. We obtained 30 rest-frame FUV-to-FIR spectral energy distributions (SEDs) of LBGs at z ∼ 3, and analyzed these with the CIGALE SED-fitting analysis code. We were able to derive fully consistent physical parameters, that is, M*, βUV, LFUV, LIR, AFUV, star formation rate, and the slope of the dust attenuation law; we built a semiempirical library of 30 rest-frame FUV-to-FIR stacked LBG SEDs as functions of LFUV, βUV, and M*. Results. We used the so-called IR-excess (IRX ≡ LIR/LFUV) to investigate the dust attenuation as a function of βUV and M*. Our LBGs, averaged as a function of βUV, follow the well-known IRX–βUV calibration of local starburst galaxies. Stacks as a function of M* follow the IRX–M* relationship presented in the literature at high M* (log(M* [M⊙]) &gt; 10). However, a large dispersion is shown in the IRX–βUV and IRX–M* planes, in which the βUV and M* are combined to average the sample. Additionally, the SED-fitting analysis results provide a diversity of dust attenuation curve along the LBG sample, and their slopes are well correlated with M*. Steeper dust attenuation curves than Calzetti’s are favored in low stellar mass LBGs (log(M* [M⊙]) &lt; 10.25), while grayer dust attenuation curves are favored in high stellar mass LBGs (log(M* [M⊙]) &gt; 10.25). We also demonstrate that the slope of the dust attenuation curves is one of the main drivers that shapes the IRX–βUV plane.

Cosmology with dropout selection: straw-man surveys & CMB lensing

We seek to prove the means, motive and opportunity of 'dropout' selected 2 ⩽ z ⩽ 5 galaxies for large-scale structure. Together with acquired low-z tracers, these samples would map practically every linear mode and facilitate a tomographic decomposition of the Cosmic Microwave Background (CMB) lensing kernel over an unprecedented volume. With this, one may infer (the time evolution of) matter density fluctuations and perform compelling tests of horizon-scale General Relativity, neutrino masses and Inflation—viz., curvature, running of the spectral index and a scale-dependent halo bias induced by (local) primordial non-Gaussianity. This is facilitated by the order-of-magnitude increase in sensitivity achieved by planned CMB, optical-to-near-infrared imaging and spectroscopy. Focusing on traditional color-color—rather than photometric redshift—selection, we estimate the expected completeness, contamination, and spectroscopic survey speed of tailored Lyman-break galaxy (LBG) samples. With these in hand, we forecast the potential of CMB lensing cross-correlation, `clustering redshifts' and Redshift-Space Distortions (RSD) analyses. In particular, we estimate: the depth dependence of interlopers based on CFHTLS-Archive-Research Survey (CARS) data and propagate this to biases in cosmology; a simple relation for the dependence of the linear galaxy bias on redshift and depth; new inferences of non-linear halo bias at these redshifts using legacy data; detailed forecasts of LBG spectra as would be observed by the Dark Energy Spectroscopic Instrument, Prime Focus Spectrograph, and their successors. We further assess the relative competitiveness of these spectroscopic facilities based on an intuitive figure-of-merit and define modern equivalents to traditional color selection criteria for the Large Synoptic Survey Telescope, where necessary. We confirm these science cases to be compelling for achievable facilities in the next decade by defining a LBG sample of increasing Lyman-α equivalent width with redshift, which delivers both percent-level RSD constraints on the growth rate at high-z and measurements of CMB lensing cross-correlation at z=3 and 4 with a significance measured in the hundreds, given sufficient area overlap. Finally, we discuss the limitations of this initial exploration and provide avenues for future investigation.

Deep into the structure of the first galaxies: SERRA views

We study the formation and evolution of a sample of Lyman Break Galaxies in the Epoch of Reionization by using high-resolution ($\sim 10 \,{\rm pc}$), cosmological zoom-in simulations part of the SERRA suite. In SERRA, we follow the interstellar medium (ISM) thermo-chemical non-equilibrium evolution, and perform on-the-fly radiative transfer of the interstellar radiation field (ISRF). The simulation outputs are post-processed to compute the emission of far infrared lines ([CII], [NII], and [OIII]). At $z=8$, the most massive galaxy, `Freesia', has an age $t_\star \simeq 409\,{\rm Myr}$, stellar mass $M_{\star} \simeq 4.2\times 10^9 {\rm M}_{\odot}$, and a star formation rate ${\rm SFR} \simeq 11.5\,{\rm M}_{\odot}{\rm yr}^{-1}$, due to a recent burst. Freesia has two stellar components (A and B) separated by $\simeq 2.5\, {\rm kpc}$; other 11 galaxies are found within $56.9 \pm 21.6 \, {\rm kpc}$. The mean ISRF in the Habing band is $G = 7.9\, G_0$ and is spatially uniform; in contrast, the ionisation parameter is $U = 2^{+20}_{-2} \times 10^{-3}$, and has a patchy distribution peaked at the location of star-forming sites. The resulting ionising escape fraction from Freesia is $f_{\rm esc}\simeq 2\%$. While [CII] emission is extended (radius 1.54 kpc), [OIII] is concentrated in Freesia-A (0.85 kpc), where the ratio $\Sigma_{\rm [OIII]}/\Sigma_{\rm [CII]} \simeq 10$. As many high-$z$ galaxies, Freesia lies below the local [CII]-SFR relation. We show that this is the general consequence of a starburst phase (pushing the galaxy above the Kennicutt-Schmidt relation) which disrupts/photodissociates the emitting molecular clouds around star-forming sites. Metallicity has a sub-dominant impact on the amplitude of [CII]-SFR deviations.

The Universe Is Reionizing at z ∼ 7: Bayesian Inference of the IGM Neutral Fraction Using Lyα Emission from Galaxies

Abstract We present a new flexible Bayesian framework for directly inferring the fraction of neutral hydrogen in the intergalactic medium (IGM) during the Epoch of Reionization (EoR, z ∼ 6–10) from detections and non-detections of Lyman Alpha (Lyα) emission from Lyman Break galaxies (LBGs). Our framework combines sophisticated reionization simulations with empirical models of the interstellar medium (ISM) radiative transfer effects on Lyα. We assert that the Lyα line profile emerging from the ISM has an important impact on the resulting transmission of photons through the IGM, and that these line profiles depend on galaxy properties. We model this effect by considering the peak velocity offset of Lyα lines from host galaxies’ systemic redshifts, which are empirically correlated with UV luminosity and redshift (or halo mass at fixed redshift). We use our framework on the sample of LBGs presented in Pentericci et al. and infer a global neutral fraction at z ∼ 7 of , consistent with other robust probes of the EoR and confirming that reionization is ongoing ∼700 Myr after the Big Bang. We show that using the full distribution of Lyα equivalent width detections and upper limits from LBGs places tighter constraints on the evolving IGM than the standard Lyα emitter fraction, and that larger samples are within reach of deep spectroscopic surveys of gravitationally lensed fields and James Webb Space Telescope NIRSpec.

Size–Luminosity Relations and UV Luminosity Functions at z = 6–9 Simultaneously Derived from the Complete Hubble Frontier Fields Data

Abstract We construct z ∼ 6–7, 8, and 9 faint Lyman break galaxy samples (334, 61, and 37 galaxies, respectively) with accurate size measurements with the software glafic from the complete Hubble Frontier Fields (HFF) cluster and parallel fields data. These are the largest samples hitherto and reach down to the faint ends of recently obtained deep luminosity functions. At faint magnitudes, however, these samples are highly incomplete for galaxies with large sizes, implying that derivation of the luminosity function sensitively depends on the intrinsic size–luminosity relation. We thus conduct simultaneous maximum-likelihood estimation of luminosity function and size–luminosity relation parameters from the observed distribution of galaxies on the size–luminosity plane with the help of a completeness map as a function of size and luminosity. At z ∼ 6–7, we find that the intrinsic size–luminosity relation expressed as r e ∝ L β has a notably steeper slope of than those at lower redshifts, which in turn implies that the luminosity function has a relatively shallow faint-end slope of . This steep β can be reproduced by a simple analytical model in which smaller galaxies have lower specific angular momenta. The β and α values for the z ∼ 8 and 9 samples are consistent with those for z ∼ 6–7 but with larger errors. For all three samples, there is a large, positive covariance between β and α, implying that the simultaneous determination of these two parameters is important. We also provide new strong lens mass models of Abell S1063 and Abell 370, as well as updated mass models of Abell 2744 and MACS J0416.1−2403.

Lyman-break Galaxies at z ∼ 3 in the Subaru Deep Field: Luminosity Function, Clustering, and [O iii] Emission

Abstract We combined deep U-band and optical/near-infrared imaging, in order to select Lyman Break Galaxies (LBGs) at z ∼ 3 using U − V and V − R c colors in the Subaru Deep Field. The resulting sample of 5161 LBGs gives a UV luminosity function (LF) down to M UV = − 18 , with a steep faint-end slope of α = − 1.78 ± 0.05 . We analyze UV-to-NIR energy distributions (SEDs) from optical photometry and photometry on IR median-stacked images. In the stacks, we find a systematic background depression centered on the LBGs. This results from the difficulty of finding faint galaxies in regions with higher-than-average surface densities of foreground galaxies, so we corrected for this deficit. Best-fit stellar population models for the LBG SEDs indicate stellar masses and star formation rates of log 10 ( M * / M ⊙ ) ≃ 10 and ≃ 50 M ⊙ yr−1 at 〈 i AB ′ 〉 = 24 , down to log 10 ( M * / M ⊙ ) ≃ 8 and ≃ 3 M ⊙ yr−1 at 〈 i AB ′ 〉 = 27 . The faint LBGs show a ∼1 mag excess over the stellar continuum in K-band. We interpret this excess flux as redshifted [O iii] λ λ 4959,5007 lines. The observed excesses imply equivalent widths that increase with decreasing mass, reaching EW 0 ( [ O iii ] 4959 , 5007 + H β ) ≳ 1500 Å (rest-frame). Such strong [O iii] emission is seen only in a miniscule fraction of local emission-line galaxies, but is probably universal in the faint galaxies that reionized the universe. Our halo occupation distribution analysis of the angular correlation function gives a halo mass of log 10 ( 〈 M h 〉 / h − 1 M ⊙ ) = 11.29 ± 0.12 for the full sample of LBGs, and log 10 ( 〈 M h 〉 / h − 1 M ⊙ ) = 11.49 ± 0.1 for the brightest half of the sample.

Dust masses of z &gt; 5 galaxies from SED fitting and ALMA upper limits

We aim at constraining the dust mass in high-redshift ($z\gtrsim 5$) galaxies using the upper limits obtained by ALMA in combination with the rest-frame UV--optical spectral energy distributions (SEDs). For SED fitting, because of degeneracy between dust extinction and stellar age, we focus on two extremes: continuous star formation (Model A) and instantaneous star formation (Model B). We apply these models to Himiko (as a representative UV-bright object) and a composite SED of $z>5$ Lyman break galaxies (LBGs). For Himiko, Model A requires a significant dust extinction, which leads to a high dust temperature $>70$ K for consistency with the ALMA upper limit. This high dust temperature puts a strong upper limit on the total dust mass $M_\mathrm{d}\lesssim 2\times 10^6$ M$_{\odot}$, and the dust mass produced per supernova (SN) $m_\mathrm{d,SN}\lesssim 0.1$ M$_{\odot}$. Such a low $m_\mathrm{d,SN}$ suggests significant loss of dust by reverse shock destruction or outflow, and implies that SNe are not the dominant source of dust at high $z$. Model B allows $M_\mathrm{d}\sim 2\times 10^7$ M$_{\odot}$ and $m_\mathrm{d,SN}\sim 0.3$ M$_{\odot}$.} We could distinguish between Models A and B if we observe Himiko at {wavelength $<$ 1.2 mm by ALMA. For the LBG sample, we obtain $M_\mathrm{d}\lesssim 2\times 10^6$ M$_{\odot}$ for a typical LBG at $z>5$, but this only puts an upper limit for $m_\mathrm{d,SN}$ as $\sim 2$ M$_{\odot}$. This clarifies the importance of observing UV-bright objects (like Himiko) to constrain the dust production by SNe.

Characterization and Modeling of Contamination for Lyman Break Galaxy Samples at High Redshift

Abstract The selection of high-redshift sources from broadband photometry using the Lyman-break galaxy (LBG) technique is a well established methodology, but the characterization of its contamination for the faintest sources is still incomplete. We use the optical and near-IR data from four (ultra)deep Hubble Space Telescope legacy fields to investigate the contamination fraction of LBG samples at selected using a color–color method. Our approach is based on characterizing the number count distribution of interloper sources, that is, galaxies with colors similar to those of LBGs, but showing detection at wavelengths shorter than the spectral break. Without sufficient sensitivity at bluer wavelengths, a subset of interlopers may not be properly classified, and contaminate the LBG selection. The surface density of interlopers in the sky gets steeper with increasing redshift of LBG selections. Since the intrinsic number of dropouts decreases significantly with increasing redshift, this implies increasing contamination from misclassified interlopers with increasing redshift, primarily by intermediate redshift sources with unremarkable properties (intermediate ages, lack of ongoing star formation and low/moderate dust content). Using Monte-Carlo simulations, we estimate that the CANDELS deep data have contamination induced by photometric scatter increasing from at to at for a typical dropout color mag, with contamination naturally decreasing for a more stringent dropout selection. Contaminants are expected to be located preferentially near the detection limit of surveys, ranging from 0.1 to 0.4 contaminants per arcmin2 at = 30, depending on the field considered. This analysis suggests that the impact of contamination in future studies of galaxies needs to be carefully considered.