Ultraviolet Luminosity Research Articles

JWST UNCOVER: the overabundance of ultraviolet-luminous galaxies at z > 9

ABSTRACT Over the past year, JWST has uncovered galaxies at record-breaking distances up to z ∼ 13. The JWST UNCOVER (ultra-deep NIRSpec and NIRcam observations before the epoch of reionization) program has obtained ultra-deep multiwavelength NIRCam imaging of the massive galaxy cluster A2744 over ∼45 arcmin2 down to ∼29.5 AB mag. Here, we present a robust ultraviolet (UV) luminosity function derived through lensing clusters at 9 < z < 12. Using comprehensive end-to-end simulations, we account for all lensing effects and systematic uncertainties in deriving both the amplification factors and the effective survey volume. Our results confirm the intriguing excess of UV-bright galaxies (MUV <−20 AB mag) previously reported at z > 9 in recent JWST studies. In particular, a double power-law (DPL) describes better the bright end of the luminosity function compared to the classical Schechter form. The number density of these bright galaxies is 10–100 times larger than theoretical predictions and previous findings based on Hubble Space Telescope (HST) observations. Additionally, we measure a star formation rate density of ρSFR = 10−2.64 M⊙ yr−1 Mpc−3 at these redshifts, which is 4–10 times higher than galaxy formation models that assume a constant star formation efficiency. Future wide-area surveys and accurate modelling of lensing-assisted observations will reliably constrain both the bright and the dim end of the UV luminosity function at z > 9, which will provide key benchmarks for galaxy formation models.

On the bright end of the UV luminosity functions of galaxies at z ∼ 0.6–1.2

ABSTRACT We derive the ultraviolet (UV) luminosity function (LF) of star-forming galaxies in the redshift range z = 0.6–1.2, in the rest-frame far-UV (1500 Å) wavelength. For this work, we are in particular interested in the bright end of the UV LF in this redshift range. Data from the XMM–Newton Optical Monitor (XMM-OM), near-UV (2410–3565 Å) observations over 1.5 deg2 of the Cosmic evolution survey (COSMOS) field are employed for this purpose. We compile a source list of 879 sources with UVW1AB in the range ∼21–24 mag from the wide-area UVW1 image of the COSMOS field in the two bins 0.6 ≤ z ≤ 0.8 and 0.8 ≤ z ≤ 1.2. The M1500 for these sources lies in the interval [ − 19.10, −22.50]. We use the maximum likelihood to fit a Schechter function model to the unbinned data to estimate the parameters (faint-end slope, characteristic magnitude, and normalization) of the Schechter function. We find the shape of the LF to be consistent with the Schechter model, and the parameters are in fair agreement with other studies conducted using direct measurements of the 1500 Å flux. We see a brightening of the characteristic magnitude as we move from lower (0.7) to higher (1.0) redshift. The measures for luminosity density are within the error margins of past studies. We examine the brightest sources in our sample for the active galactic nucleus contribution. These sources are characterized by their spectral energy distributions, integrated infrared (IR) luminosities, and morphologies. We also explore their overlap with the brightest IR galaxies in a similar redshift range.

Constraints on cosmological models from quasars calibrated with type Ia supernova by a Gaussian process

ABSTRACT In this paper, we use quasars calibrated from type Ia supernova (SN Ia) to constrain cosmological models. We consider three different X-ray luminosity (LX)–ultraviolet luminosity (LUV) relations of quasars, i.e. the standard LX–LUV relation and two redshift–evolutionary relations (Type I and Type II), respectively, constructed from copula and considering a redshift correction to the luminosity of quasars. Only in the case of the Type I relation, quasars can always provide effective constraints on the ΛCDM (cosmological constant Λ plus cold dark matter) model. Furthermore, we show that, when the observational Hubble data (OHD) are added, the constraints on the absolute magnitude M of SN Ia and the Hubble constant H0 can be obtained. In the ΛCDM model, the OHD measurements plus quasars with the Type I relation yields M = $-19.321^{+0.085}_{-0.076}$, which is in good agreement with the measurement from SH0ES (M = −19.253 ± 0.027), and H0 = $70.80\pm 3.6~\mathrm{km~s^{-1}\, Mpc^{-1}}$, falling between the measurements from SH0ES and the Planck cosmic microwave background radiation data.

EPOCHS. II. The Ultraviolet Luminosity Function from 7.5 < z < 13.5 Using 180 arcmin2 of Deep, Blank Fields from the PEARLS Survey and Public JWST Data

We present an analysis of the ultraviolet luminosity function (UV LF) and star formation rate density of distant galaxies (7.5 < z < 13.5) in the “blank” fields of the Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) survey combined with Early Release Science data from the CEERS, GLASS, and NGDEEP surveys/fields and the first data release of JADES. We use strict quality cuts on EAZY photometric redshifts to obtain a reliable selection and characterization of high-redshift (z > 6.5) galaxies from a consistently processed set of deep, near-infrared imaging. Within an area of 180 arcmin2, we identify 1046 candidate galaxies at redshifts z > 6.5 and we use this sample to study the UV LF in four redshift bins between 7.5 < z < 13.5. The measured number density of galaxies at z = 8 and z = 9 matches those of past observations undertaken by the Hubble Space Telescope (HST). Our z = 10.5 measurements lie between early James Webb Space Telescope (JWST) results and past HST results, indicating cosmic variance may be the cause of previous high density measurements. However, the number densities of UV-luminous galaxies at z = 12.5 are high compared to predictions from simulations. When examining the star formation rate density of galaxies at this period, our observations are still largely consistent with a constant star formation efficiency, are slightly lower than previous early estimations using JWST, and support galaxy driven reionization at z ≤ 8.

Adding value to JWST spectra and photometry: stellar population and star formation properties of spectroscopically confirmed JADES and CEERS galaxies at z &amp;gt; 7

ABSTRACT In this paper, we discuss measurements of the stellar population and star-forming properties for 43 spectroscopically confirmed publicly available high-redshift z &amp;gt; 7 JWST galaxies in the JADES and CEERS observational programs. We carry out a thorough study investigating the relationship between spectroscopic features and photometrically derived ones, including from spectral energy distribution (SED) fitting of models, as well as morphological and structural properties. We find that the star formation rates (SFRs) measured from H β line emission are higher than those estimated from Bayesian SED fitting and ultraviolet (UV) luminosity, with ratios SFRH β/SFRUV ranging from ∼2 to 13. This is a sign that the star formation history is consistently rising given the time-scales of H β versus UV star formation probes. In addition, we investigate how well equivalent widths (EWs) of H β λ4861, [O iii] λ4959, and [O iii] λ5007 can be measured from photometry, finding that, on average, the EW derived from photometric excesses in filters is 30 per cent smaller than the direct spectroscopic measurement. We also discover that a stack of the line emitting galaxies shows a distinct morphology after subtracting imaging that contains only the continuum. This gives us a first view of the line or ionized gas emission from z &amp;gt; 7 galaxies, demonstrating that this material has a similar distribution, statistically, as the continuum. We also compare the derived SFRs and stellar masses for both parametric and non-parametric star formation histories, where we find that 35 per cent of our sample formed at least 30 per cent of their stellar mass in recent (&amp;lt;10 Myr) starburst events.

Exploring the nature of UV-bright z ≳ 10 galaxies detected by JWST: star formation, black hole accretion, or a non-universal IMF?

ABSTRACT We use the Cosmic Archaeology Tool (CAT) semi-analytical model to explore the contribution of Population (Pop) III/II stars and active galactic nuclei (AGNs) to the galaxy ultraviolet (UV) luminosity function (LF) evolution at 4 ≤ z ≤ 20. We compare in particular with recent JWST data in order to explore the apparent tension between observations and theoretical models in the number density of bright galaxies at z ≳ 10. The model predicts a star formation history dominated by UV faint (MUV &amp;gt; −18) galaxies, with a Pop III contribution of $\lesssim 10~{{\ \rm per\ cent}}$ ($\lesssim 0.5~{{\ \rm per\ cent}}$) at z ≃ 20 (z ≃ 10). Stars are the primary sources of cosmic reionization, with $5~{{\ \rm per\ cent}}\!-\!10~{{\ \rm per\ cent}}$ of ionizing photons escaping into the intergalatic medium at 5 ≤ z ≤ 10, while the contribution of unobscured AGNs becomes dominant only at z ≲ 5. The predicted stellar and AGN UV LFs reproduce the observational data at 5 ≲ z ≲ 9–10. At higher redshift, CAT predicts a steeper evolution in the faint-end slope (MUV &amp;gt; –18), and a number density of bright galaxies (MUV ≃ −20) consistent with data at z ∼ 10–11, but smaller by 0.8 dex at z ∼ 12–13, and 1.2 dex at z ∼ 14–16, when compared to the values estimated by recent studies. Including the AGN emission does not affect the above findings, as AGNs contribute at most to $\lesssim 10~{{\ \rm per\ cent}}$ of the total UV luminosity at MUV &amp;lt; –19 and z ≳ 10. Interestingly, considering a gradual transition in the stellar initial mass function, modulated by metallicity and redshift as suggested by recent simulations, the model agrees with JWST data at z ∼ 12–13, and the disagreement at z ∼ 14–16 is reduced to 0.5 dex.

Insight from JWST/Near Infrared Camera into galaxy overdensities around bright Lyman-alpha emitters during reionization: implications for ionized bubbles at z ∼ 9

ABSTRACT Several studies have detected Lyman-alpha (Ly α) from bright ($M_{\small UV}\lesssim -21.5$) galaxies during the early stages of reionization despite the significantly neutral intergalactic medium. To explain these detections, it has been suggested that z &amp;gt; 7 Ly α emitters (LAEs) inhabit physical Mpc (pMpc)-scale ionized regions powered by overdensities of faint galaxies; however, systematic searches for these overdensities near LAEs have been challenging. Here, we use Cosmic Evolution Early Release Science JWST/Near Infrared Camera imaging to search for large-scale galaxy overdensities near two very ultraviolet (UV)-bright, z = 8.7 LAEs in the Extended Groth Strip (EGS) field. We colour select 27 z = 8.4–9.1 candidates, including the one LAE in the footprint (EGSY8p7). From spectral energy distribution models, we infer moderately faint UV luminosities ($-21.2\lesssim {M_{\small UV}}\lesssim -19.1$) and stellar masses of M* ≈ 107.5–8.8 M⊙. All are efficient ionizing agents ($\xi _{\text{ion}}^{*}\approx 10^{25.5-26.0}$ Hz erg−1) and are generally morphologically simple with only one compact (re ≲ 140 to ∼650 pc) star-forming component. 13 candidates lie within 5 arcmin of EGSY8p7, leading to a factor-of-four galaxy overdensity at ≲5 arcmin (∼1.4 projected pMpc at z ∼ 8.7) separations from EGSY8p7. Separations of 10–15 arcmin (∼2.7–4.1 projected pMpc) are consistent with an average field. The spatial distribution of our sample may qualitatively suggest an R ≥ 2 pMpc ionized bubble encompassing both LAEs in EGS, which is theoretically unexpected but may be possible for a galaxy population four times more numerous than the average to create with moderate escape fractions (fesc ≳ 0.15) over long times (≳ 200 Myr). Upcoming spectroscopic follow-up will characterize the size of any ionized bubble that may exist and the properties of the galaxies powering such a bubble.

Observations Favor the Redshift-evolutionary L X–L UV Relation of Quasars from Copula

We compare, with data from quasars, Hubble parameter measurements, and Pantheon+ type Ia supernova, three different relations between X-ray luminosity (L X) and ultraviolet luminosity (L UV) of quasars. These three relations consist of the standard and two redshift-evolutionary L X–L UV relations, which are constructed, respectively, by considering a redshift-dependent correction to the luminosities of quasars and using the statistical tool copula. By employing the PAge approximation for a cosmological model–independent description of the cosmic background evolution and dividing the quasar data into the low-redshift and high-redshift parts, we find that the constraints on the PAge parameters from the low-redshift and high-redshift data, which are obtained with the redshift-evolutionary relations, are consistent with each other, while they are not when the standard relation is considered. If the data are used to constrain the coefficients of the relations and the PAge parameters simultaneously, then the observations support the redshift-evolutionary relations at more than 3σ. The Akaike and Bayes information criteria indicate that there is strong evidence against the standard relation and mild evidence against the redshift-evolutionary relation constructed by considering a redshift-dependent correction to the luminosities of quasars. This suggests that the redshift-evolutionary L X–L UV relation of quasars constructed from copula is favored by the observations.

On the dust properties of the UV galaxies in the redshift range z ∼ 0.6–1.2

ABSTRACT Far-infrared observations from the Herschel Space Observatory are used to estimate the infrared (IR) properties of ultraviolet-selected galaxies. We stack the PACS (100, 160 $\mu$m) and SPIRE (250, 350, and 500 $\mu$m) maps of the Chandra deep field south (CDFS) on a source list of galaxies selected in the rest-frame ultraviolet (UV) in a redshift range of 0.6–1.2. This source list is created using observations from the XMM–OM telescope survey in the CDFS using the UVW1 (2910 Å) filter. The stacked data are binned according to the UV luminosity function of these sources, and the average photometry of the UV-selected galaxies is estimated. By fitting modified black bodies and IR model templates to the stacked photometry, average dust temperatures and total IR luminosity are determined. The luminosity-weighted average temperatures are consistent with a weak trend of increasing temperature with redshift found by previous studies. Infrared excess, unobscured, and obscured star formation rate (SFR) values are obtained from the UV and IR luminosities. We see a trend in which dust attenuation increases as UV luminosity decreases. It remains constant as a function of IR luminosities at fixed redshift across the luminosity range of our sources. In comparison to local luminous infrared galaxies with similar SFRs, the higher redshift star-forming galaxies in the sample show a lesser degree of dust attenuation. Finally, the inferred dust attenuation is used to correct the unobscured SFR density in the redshift range 0.6–1.2. The dust-corrected SFR density is consistent with measurements from IR-selected samples at similar redshifts.

The Star Formation Efficiency during Reionization as Inferred from the Hubble Frontier Fields

A recent ultraviolet luminosity function (UVLF) analysis in the Hubble Frontier Fields, behind foreground lensing clusters, has helped solidify estimates of the faint-end of the z ∼ 5–9 UVLF at up to 5 mag fainter than in the field. These measurements provide valuable information regarding the role of low-luminosity galaxies in reionizing the universe and can help in calibrating expectations for JWST observations. We fit a semiempirical model to the lensed and previous UVLF data from Hubble. This fit constrains the average star formation efficiency (SFE) during reionization, with the lensed UVLF measurements probing halo mass scales as small as M ∼ 2 × 109 M ⊙. The implied trend of SFE with halo mass is broadly consistent with an extrapolation from previous inferences at M ≳ 1010 M ⊙, although the joint data prefer a shallower SFE. This preference, however, is partly subject to systematic uncertainties in the lensed measurements. Near z ∼ 6, we find that the SFE peaks at ∼20% between ∼1011 and 1012 M ⊙. Our best-fit model is consistent with the Planck 2020 determinations of the electron scattering optical depth, and most current reionization history measurements, provided the escape fraction of ionizing photons is f esc ∼ 10%–20%. The joint UVLF accounts for nearly 80% of the ionizing photon budget at z ∼ 8. Finally, we show that recent JWST UVLF estimates at z ≳ 11 require strong departures from the redshift evolution suggested by the Hubble data.

21cmemu: an emulator of 21cmfast summary observables

ABSTRACT Recent years have witnessed rapid progress in observations of the epoch of reionization (EoR). These have enabled high-dimensional inference of galaxy and intergalactic medium (IGM) properties during the first billion years of our Universe. However, even using efficient, seminumerical simulations, traditional inference approaches that compute 3D lightcones on-the-fly can take 105 core hours. Here we present 21cmemu: an emulator of several summary observables from the popular 21cmfast simulation code. 21cmemu takes as input nine parameters characterizing EoR galaxies, and outputs the following summary statistics: (i) the IGM mean neutral fraction; (ii) the 21-cm power spectrum; (iii) the mean 21-cm spin temperature; (iv) the sky-averaged (global) 21-cm signal; (vi) the ultraviolet (UV) luminosity functions (LFs); and (vii) the Thomson scattering optical depth to the cosmic microwave background (CMB). All observables are predicted with sub- per cent median accuracy, with a reduction of the computational cost by a factor of over 104. After validating inference results, we showcase a few applications, including: (i) quantifying the relative constraining power of different observational data sets; (ii) seeing how recent claims of a late EoR impact previous inferences; and (iii) forecasting upcoming constraints from the sixth observing season of the Hydrogen Epoch of Reionization Array (HERA) telescope. 21cmemu is publicly available, and is included as an alternative simulator in the public 21cmmc sampler.

Validating Posteriors Obtained by an Emulator When Jointly Fitting Mock Data of the Global 21 cm Signal and High-z Galaxy UV Luminosity Function

Although neural-network-based emulators enable efficient parameter estimation in 21 cm cosmology, the accuracy of such constraints is poorly understood. We employ nested sampling to fit mock data of the global 21 cm signal and high-z galaxy ultraviolet luminosity function (UVLF) and compare for the first time the emulated posteriors obtained using the global signal emulator globalemu to the “true” posteriors obtained using the full model on which the emulator is trained using ARES. Of the eight model parameters we employ, four control the star formation efficiency (SFE) and thus can be constrained by UVLF data, while the remaining four control UV and X-ray photon production and the minimum virial temperature of star-forming halos () and thus are uniquely probed by reionization and 21 cm measurements. For noise levels of 50 and 250 mK in the 21 cm data being jointly fit, the emulated and “true” posteriors are consistent to within 1σ. However, at lower noise levels of 10 and 25 mK, globalemu overpredicts and underpredicts γ lo, an SFE parameter, by ≈3σ–4σ, while the “true” ARES posteriors capture their fiducial values within 1σ. We find that jointly fitting the mock UVLF and 21 cm data significantly improves constraints on the SFE parameters by breaking degeneracies in the ARES parameter space. Our results demonstrate the astrophysical constraints that can be expected for global 21 cm experiments for a range of noise levels from pessimistic to optimistic, as well as the potential for probing redshift evolution of SFE parameters by including UVLF data.

First Light and Reionization Epoch Simulations (flares) – XIV. The Balmer/4000 Å breaks of distant galaxies

ABSTRACT With the successful launch and commissioning of JWST we are now able to routinely spectroscopically probe the rest-frame optical emission of galaxies at z &amp;gt; 6 for the first time. Among the most useful spectral diagnostics used in the optical is the Balmer/4000 Å break; this is, in principle, a diagnostic of the mean ages of composite stellar populations. However, the Balmer break is also sensitive to the shape of the star formation history, the stellar (and gas) metallicity, the presence of nebular continuum emission, and dust attenuation. In this work, we explore the origin of the Balmer/4000 Å break using the synthesizer synthetic observations package. We then make predictions of the Balmer/4000 Å break using the First Light and Reionization Epoch Simulations at 5 &amp;lt; z &amp;lt; 10. We find that the average break strength weakly correlates with stellar mass and rest-frame far-ultraviolet luminosity, but that this is predominantly driven by dust attenuation. We also find that break strength provides a weak diagnostic of the age but performs better as a means to constrain star formation and stellar mass, alongside the ultraviolet and optical luminosity, respectively.

Dark-ages reionization and galaxy formation simulation – XXI. Constraining the evolution of the ionizing escape fraction

ABSTRACT The fraction of ionizing photons that escape their host galaxies to ionize hydrogen in the intergalactic medium (IGM) is a critical parameter in analyses of the reionization era. In this paper, we use the meraxes semi-analytic galaxy formation model to infer the mean ionizing photon escape fraction and its dependence on galaxy properties through joint modelling of the observed high redshift galaxy population and existing constraints on the reionization history. Using a Bayesian framework, and under the assumption that escape fraction is primarily related to halo mass, we find that the joint constraints of the ultraviolet luminosity function, cosmic microwave background optical depth, and the Ly α forest require an escape fraction of $(18\pm 5)$ per cent for galaxies within haloes of M ≲ 109 M⊙ and $(5\pm 2)$ per cent for more massive haloes. In terms of galaxy properties, this transition in escape fraction occurs at stellar masses of M⋆ ∼ 107 M⊙, nearly independent of redshift. As a function of redshift, reionization is dominated by the smaller M⋆ ≲ 107 M⊙ galaxies with high escape fractions at z ≳ 6 and by the larger M⋆ ≳ 107 M⊙ galaxies with lower escape fractions at z ≲ 6. Galaxies with star formation rates of 10−2.5 M⊙yr−1 to 10−1.5 M⊙yr−1 provide the dominant source of ionizing photons throughout reionization. Our results are consistent with recent direct measurements of a $\sim 5~{{\ \rm per\ cent}}$ escape fraction from massive galaxies at the end of reionization and support the picture of low mass galaxies being the dominant sources of ionizing photons during reionization.

The galaxy UV luminosity function at z ≃ 11 from a suite of public JWST ERS, ERO, and Cycle-1 programs

ABSTRACT We present a new determination of the evolving galaxy ultraviolet (UV) luminosity function (LF) over the redshift range 9.5 &amp;lt; z &amp;lt; 12.5 based on a wide-area (&amp;gt;250 arcmin2) data set of JWST NIRCam near-infrared imaging assembled from 13 public JWST surveys. Our relatively large-area search allows us to uncover a sample of 61 robust z &amp;gt; 9.5 candidates detected at ≥8σ, and hence place new constraints on the intermediate-to-bright end of the UV LF. When combined with our previous JWST + UltraVISTA results, this allows us to measure the form of the LF over a luminosity range corresponding to four magnitudes (M1500). At these early times we find that the galaxy UV LF is best described by a double power-law function, consistent with results obtained from recent ground-based and early JWST studies at similar redshifts. Our measurements provide further evidence for a relative lack of evolution at the bright-end of the UV LF at z = 9–11, but do favour a steep faint-end slope (α ≤ −2). The luminosity-weighted integral of our evolving UV LF provides further evidence for a gradual smooth (exponential) decline in co-moving star-formation rate density (ρSFR) at least out to z ≃ 12, with our determination of ρSFR(z = 11) lying significantly above the predictions of many theoretical models of galaxy evolution.

Inferring reionization and galaxy properties from the patchy kinetic Sunyaev–Zel’dovich signal

ABSTRACT The patchy kinetic Sunyaev–Zel’dovich (kSZ) signal is an integral probe of the timing and morphology of the epoch of reionization (EoR). Recent observations have claimed a low signal-to-noise (S/N) measurement, with a dramatic increase in S/N expected in the near future. In this work, we quantify what we can learn about the EoR from the kSZ signal. We perform Bayesian inference by sampling galaxy properties and using forward-models of the kSZ as well as other EoR and galaxy observations in the likelihood. Including the recent kSZ measurement obtained by the South Pole Telescope ($\mathcal {D}_{3000}^{\textrm {pkSZ}} = 1.1_{-0.7}^{+1.1} \mu$ K2) shifts the posterior distribution in favour of faster and later reionization models, resulting in lower values of the optical depth to the cosmic microwave background: $\tau _e = 0.052_{-0.008}^{+0.009}$ with a 68 per cent confidence interval (CI). The combined EoR and ultraviolet luminosity function observations also imply a typical ionizing escape fraction of $0.04_{-0.03}^{+0.05}$ (95 per cent CI), without a strong dependence on halo mass. We show how the patchy kSZ power from our posterior depends on the midpoint and duration of reionization: a popular parametrization of EoR timing. For a given midpoint and duration, the EoR morphology only has a few per cent impact on the patchy kSZ power in our posterior. However, a physical model is needed to obtain tight constraints from the current low S/N patchy kSZ measurement, as it allows us to take advantage of complimentary high-z observations. Future high S/N detections of the patchy kSZ should decrease the current uncertainties on the timing of the EoR by factors of ∼2–3.

Ultraluminous quasars at high redshift show evolution in their radio-loudness fraction in both redshift and ultraviolet luminosity

ABSTRACT We take a sample of 94 ultraluminous, optical quasars from the search of over 14 486 deg2 by Onken et al. in the range 4.4 &amp;lt; redshift &amp;lt; 5.2 and match them against the Rapid ASKAP Continuum Survey (RACS) observed on the Australian Square Kilometre Array Pathfinder (ASKAP). From this most complete sample of the bright end of the redshift ∼5 quasar luminosity function, there are 10 radio continuum detections, of which eight are considered radio-loud quasars. The radio-loud fraction for this sample is 8.5 ± 2.9 per cent. Jiang et al. found that there is a decrease in the radio-loud fraction of quasars with increasing redshift and an increase with increasing absolute magnitude at rest frame 2500 Å. We show that the radio-loud fraction of our quasar sample is consistent with that predicted by Jiang et al.,extending their result to higher redshifts.

Modeling the JWST High-redshift Galaxies with a General Formation Scenario and the Consistency with the ΛCDM Model

Early results from the James Webb Space Telescope (JWST) observations have hinted at two traces beyond the standard cosmological framework. One is the extraordinarily high stellar masses and their density at z = 7.5 ∼ 9.1; another is the unexpected abundance of ultraviolet (UV) bright galaxies at z ≥ 10. Nevertheless, both pieces of evidence are not statistically robust yet. In this work, we construct rest-frame UV luminosity functions (LFs) based on a general formation model for these high-redshift galaxy candidates, since UV LFs always carry the information of stellar formation efficiency (SFE), initial mass function (IMF), dust attenuation, and other crucial elements for galaxy evolution. By updating the massive galaxies candidates with spectroscopic observations and exploring the parameter space of SFE, we are able to reasonably explain the cumulative stellar mass density within the redshift range of 7.5–9.1, with only one galaxy exhibiting unusual characteristics. We also reveal a potential nonmonotonic trend of SFE with the increasing redshift. At higher redshift (z ∼ 13), bright UV LFs can be well fitted with non–dust attenuation or top-heavy IMF for Population III stars. The Population III star scenario can also naturally account for the possible dip of the peak SFE evolution curve at z ∼ 9.

NGDEEP Epoch 1: The Faint End of the Luminosity Function at z ∼ 9–12 from Ultradeep JWST Imaging

We present a robust sample of very high redshift galaxy candidates from the first epoch of JWST/NIRCam imaging from the Next Generation Deep Extragalactic Exploratory Public (NGDEEP) survey. The NGDEEP NIRCam imaging, spanning 9.7 arcmin2 in the Hubble Ultra Deep Field Parallel Field 2, reaches m = 30.4 (5σ, point-source, 2″ diameter apertures corrected to total) in F277W, making it the deepest public JWST GO imaging data set to date. We describe our detailed data reduction process of the six-filter broadband JWST/NIRCam imaging, incorporating custom corrections for systematic effects to produce high-quality calibrated images. Using robust photometric redshift selection criteria, we identify a sample of 38 z ≳ 9 galaxy candidates. These objects span a redshift range of z = 8.5–15.8 and apparent magnitudes of m F277W = 27–30.5 AB mag, reaching ∼1.5 mag deeper than previous public JWST imaging surveys. We calculate the rest-frame ultraviolet luminosity function at z ∼ 9 and 11 and present a new measurement of the luminosity function faint-end slope at z ∼ 11. We find a faint-end slope of α = −2.5 ± 0.4 and −2.2 ± 0.2 at z ∼ 9 and 11, respectively. This is consistent with no significant evolution in the faint-end slope and number density from z = 9 to 11. Comparing our results with theoretical predictions, we find that some models produce better agreement at the faint end than the bright end. These results will help to constrain how stellar feedback impacts star formation at these early epochs.

The MUSE Ultra Deep Field (MUDF). IV. A pair of X-ray weak quasars at the heart of two extended Lyα nebulae

ABSTRACT We present the results obtained from follow-up observations of the MUSE Ultra Deep Field (MUDF) at X-ray energies with XMM–Newton. The MUDF is centred on a unique field with two bright, physically associated quasars at z ≃ 3.23, separated by ∼500 kpc in projection. Both quasars are embedded within extended Lyα nebulae (${\gtrsim}100\,{\rm kpc}$ at a surface brightness flux level of ≈6 × 10−19 ${\rm erg\,s^{-1}\,cm^{-2}\,arcsec^{-2}}$), whose elongated morphology is suggestive of an extended filament connecting the quasar haloes. The new X-ray observations presented here allow us to characterize the physical properties (e.g. X-ray slope, luminosities, gas column densities) in the innermost region of the MUDF quasars. We find that both quasars are X-ray underluminous compared to objects at similar ultraviolet luminosities. Based on our X-ray spectral analysis, absorbing columns of NH(z) ≳ 1023 cm−2 appear unlikely therefore such a weakness is possibly intrinsic. When also including literature data, we do not observe any detectable trend between the area of the nebulae and nuclear luminosities at both the rest-frame 2 keV and 2500 Å. The area is also not correlated with the X-ray photon index nor with the integrated band flux in the hard band (2–10 keV). We also do not find any trend between the extended Lyα emission of the nebulae and the nuclear X-ray luminosity. Finally, the properties of the MUDF quasars’ nebulae are consistent with the observed relation between the Lyα integrated luminosity of the nebulae and their area. Our results suggest that the quasar ionization power is not a strong driver of the morphology and size of the nebulae.