Ultra Deep Field Research Articles

Forecasting Constraint on the f(R) Theory with the CSST SN Ia and BAO Surveys

The f(R) modified gravity theory can explain the accelerating expansion of the late Universe without introducing dark energy. In this study, we predict the constraint strength on the f(R) theory using the mock data generated from the Chinese Space Station Telescope (CSST) Ultra-Deep Field Type Ia supernova (SN Ia) survey and wide-field slitless spectroscopic baryon acoustic oscillation (BAO) survey. We explore three popular f(R) models and introduce a parameter b to characterize the deviation of the f(R) theory from the ΛCDM theory. The Markov Chain Monte Carlo method is employed to constrain the parameters in the f(R) models, and the nuisance parameters and systematic uncertainties are also considered in the model fitting process. Besides, we also perform model comparisons between the f(R) models and the ΛCDM model. We find that the constraint accuracy using the CSST SN Ia+BAO data set alone is comparable to or even better than the result given by the combination of the current relevant observations, and the CSST SN Ia+BAO survey can distinguish the f(R) models from the ΛCDM model. This indicates that the CSST SN Ia and BAO surveys can effectively constrain and test the f(R) theory.

The MUSE Ultra Deep Field (MUDF). VI. The Relationship between Galaxy Properties and Metals in the Circumgalactic Medium

We present initial results associating galaxies in the Multi-Unit Spectroscopic Explorer (MUSE) Ultra Deep Field (MUDF) with gas seen in absorption along the line of sight to two bright quasars in this field to explore the dependence of metals in the circumgalactic medium (CGM) on galaxy properties. The MUDF includes ∼140 hr of Very Large Telescope (VLT)/MUSE data and 90 orbits of Hubble Space Telescope (HST)/G141M grism observations alongside VLT/Ultraviolet and Visual Echelle Spectrograph spectroscopy of the two quasars and several bands of HST imaging. We compare the metal absorption around galaxies in this field as a function of impact parameter, azimuthal angle, and galaxy metallicity across redshifts 0.5 < z < 3.2. Due to the depth of our data and a large field of view, our analysis extends to low stellar masses (<107 M ⊙) and high impact parameters (>600 kpc). We find a correlation between the absorber equivalent width and the number of nearby galaxies, but do not detect a significant anticorrelation with the impact parameter. Our full sample does not show any significant change in absorber incidence as a function of azimuthal angle. However, we do find a bimodality in the azimuthal angle distribution of absorption at small impact parameters (<2 r vir) and around highly star-forming galaxies, possibly indicating disk-like accretion and biconical outflows. Finally, we do not detect any systematic deviation from the fundamental metallicity relation among galaxies with detected absorption. This work is limited by gaps in the wavelength coverage of our current data; broader-wavelength observations with the James Webb Space Telescope will allow us to unlock the full potential of the MUDF for studying the CGM.

A galactic outflow traced by its extended Mg II emission out to a ~30 kpc radius in the Hubble Ultra Deep Field with MUSE

A galactic outflow traced by its extended Mg II emission out to a ~30 kpc radius in the Hubble Ultra Deep Field with MUSE

JADES NIRSpec initial data release for the Hubble Ultra Deep Field. Redshifts and line fluxes of distant galaxies from the deepest JWST Cycle 1 NIRSpec multi-object spectroscopy

We describe the NIRSpec component of the JWST Deep Extragalactic Survey (JADES), and provide deep spectroscopy of 253 sources targeted with the NIRSpec micro-shutter assembly in the Hubble Ultra Deep Field and surrounding GOODS-South. The multi-object spectra presented here are the deepest so far obtained with JWST, amounting to up to 28 hours in the low-dispersion ($R 30-300$) prism, and up to 7 hours in each of the three medium-resolution $R 1000$ gratings and one high-dispersion grating, G395H ($R Our low-dispersion and medium-dispersion spectra cover the wavelength range $0.6-5.3\ We describe the selection of the spectroscopic targets, the strategy for the allocation of targets to micro-shutters, and the design of the observations. We present the public release of the reduced 2D and 1D spectra, and a description of the reduction and calibration process. We measure spectroscopic redshifts for 178 of the objects targeted extending up to $z=13.2$. We present a catalogue of all emission lines detected at $S/N&gt;5$, and our redshift determinations for the targets. Combined with the first JADES NIRCam data release, these public JADES spectroscopic and imaging datasets provide a new foundation for discoveries of the infrared universe by the worldwide scientific community.

The Leakage of Lyman-continuum Photons from a Major Merger at z ∼ 1

We report the detection of Lyman-continuum (LyC) photons from a massive interacting system at z = 1.097 in the Hubble Ultra Deep Field. The LyC detection is made in the far-ultraviolet F154W band of the UVIT telescope on board AstroSat. Both JWST and Hubble Space Telescope (HST) imaging of the system reveal signs that it is a likely merger. In particular, high-resolution imaging in the JWST bands reveals an infrared-luminous object within the system that is faint in the bluer HST bands. The ionized gas kinematics from the MUSE-UDF data supports the merger hypothesis. We estimate that the entire system is leaking more than 8% of its ionizing photons to the intergalactic medium. The spectral-energy-distribution-derived stellar masses of the two components indicate that this is a major merger with a mass ratio of 1.13 ± 0.37. This detection hints at the potential contribution of massive interacting systems at higher redshifts, when major mergers were more frequent, to the ionizing budget of the Universe.

Metal line emission around $z&lt;1$ galaxies

We characterize, for the first time, the average extended emission in multiple lines ( and around a statistical sample of 560 galaxies at $z By stacking the Multi Unit Spectroscopic Explorer (MUSE) 3D data from two large surveys, the MUSE Analysis of Gas around Galaxies (MAGG) and the MUSE Ultra Deep Field (MUDF), we detect significant emission out to approx 40 kpc, while and emission is detected out to approx 30 kpc. Via comparisons with the nearby average stellar continuum emission, we find that the line emission at 20--30 kpc likely arises from the disk-halo interface. Combining our results with that of our previous study at $z we find that the average surface brightness increases independently with redshift over $z and with stellar mass over which is likely driven by the star formation rate as well as the physical conditions of the gas. By comparing the observed line fluxes with photoionization models, we find that the ionization parameter declines with distance, going from log q (cm $) approx 7.7 at le 5 kpc to approx 7.3 at 20--30 kpc, which reflects a weaker radiation field in the outer regions of galaxies. The gas-phase metallicity shows no significant variation over 30 kpc, with a metallicity gradient of approx 0.003 dex kpc$^ $, which indicates an efficient mixing of metals on these scales. Alternatively, there could be a significant contribution from shocks and diffuse ionized gas to the line emission in the outer regions.

Glimmers in the Cosmic Dawn: A Census of the Youngest Supermassive Black Holes by Photometric Variability* * This research is based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 526555. These observations are associated with

We report the first results from a deep near-infrared campaign with the Hubble Space Telescope to obtain late-epoch images of the Hubble Ultra Deep Field, 10–15 yr after the first epoch data were obtained. The main objectives are to search for faint active galactic nuclei (AGN) at high redshifts by virtue of their photometric variability and measure (or constrain) the comoving number density of supermassive black holes (SMBHs), n SMBH, at early times. In this Letter, we present an overview of the program and preliminary results concerning eight objects. Three variables are supernovae, two of which are apparently hostless with indeterminable redshifts, although one has previously been recorded as a z ≈ 6 object precisely because of its transient nature. Two further objects are clear AGN at z = 2.0 and 3.2, based on morphology and/or infrared spectroscopy from JWST. Three variable targets are identified at z = 6–7 that are also likely AGN candidates. These sources provide a first measure of n SMBH in the reionization epoch by photometric variability, which places a firm lower limit of 3 × 10−4 cMpc−3. After accounting for variability and luminosity incompleteness, we estimate n SMBH ≳ 8 × 10−3 cMpc−3, which is the largest value so far reported at these redshifts. This SMBH abundance is also strikingly similar to estimates of n SMBH in the local Universe. We discuss how these results test various theories for SMBH formation.

Forming mechanism of single-channel multilayer laser cladding Fe60 process under different laser heat source operating mode

Continuous wave (CW) and pulsed wave are the two principal modes of operation used to control the laser heat source. Different laser heat source operating modes have an essential impact on the rapid cooling and heating temperature change rate during the cladding process, which directly determines the cladding layer quality. The laser cladding process is meaningful to quantitatively reveal the mechanism of single-channel multilayer cladding and forming under different laser heat source operating modes. In this article, a multi-field coupled 3D numerical model of the single-channel multilayer cladding process under different laser operating modes was proposed, and the thermal physical parameters of the cladding material were computed on the basis of Calculation of Phase Diagrams method. The mechanism of the impact of distinct operating modes on the multi-field coupled ephemeral evolution process of laser cladding was investigated by using the solid/liquid interface tracking technique, which comprehensively considers the light powder interaction between the powder waist beam and the laser beam under different operating modes. The temperature, flow, and stress fields were computationally solved for a single-channel multilayer cladding process. On the foundation of this study, the impact mechanism of pulse duty cycle and pulse frequency on the cladding behavior of single-channel and multilayers during pulsed laser cladding were dissected. The macroscopic morphology and microstructure of the cladding layer were observed by KEYENCE VH-Z100R ultra-deep field electron microscope, and the feasibility of the model was confirmed. This study provides a significant theoretical rationale for enhancing the cladding quality under different laser operating modes.

MIDIS: JWST/MIRI Reveals the Stellar Structure of ALMA-selected Galaxies in the Hubble Ultra Deep Field at Cosmic Noon

We present deep James Webb Space Telescope (JWST)/Mid-Infrared Instrument (MIRI) F560W observations of a flux-limited, Atacama Large Millimeter/submillimeter Array (ALMA)-selected sample of 28 galaxies at z = 0.5–3.7 in the Hubble Ultra Deep Field (HUDF). The data from the MIRI Deep Imaging Survey (MIDIS) reveal the stellar structure of the HUDF galaxies at rest-frame wavelengths of λ > 1 μm for the first time. We revise the stellar mass estimates using new JWST photometry and find good agreement with pre-JWST analyses; the few discrepancies can be explained by blending issues in the earlier lower-resolution Spitzer data. At z ∼ 2.5, the resolved rest-frame near-infrared (1.6 μm) structure of the galaxies is significantly more smooth and centrally concentrated than seen by the Hubble Space Telescope at rest-frame 450 nm (F160W), with effective radii of R e (F560W) = 1–5 kpc and Sérsic indices mostly close to an exponential (disk-like) profile (n ≈ 1), up to n ≈ 5 (excluding active galactic nuclei). We find an average size ratio of R e (F560W)/R e (F160W) ≈ 0.7 that decreases with stellar mass. The stellar structure of the ALMA-selected galaxies is indistinguishable from a HUDF reference sample of all galaxies with a MIRI flux density greater than 1 μJy. We supplement our analysis with custom-made, position-dependent, empirical point-spread function models for the F560W observations. The results imply that a smoother stellar structure is in place in massive gas-rich, star-forming galaxies at “Cosmic Noon,” despite a more clumpy rest-frame optical appearance, placing additional constraints on galaxy formation simulations. As a next step, matched-resolution, resolved ALMA observations will be crucial to further link the mass- and light-weighted galaxy structures to the dusty interstellar medium.

A NIRCam-dark Galaxy Detected with the MIRI/F1000W Filter in the MIDIS/JADES Hubble Ultra Deep Field

We report the discovery of Cerberus, an extremely red object detected with the MIRI Deep Imaging Survey (MIDIS) observations in the F1000W filter of the Hubble Ultra Deep Field. The object is detected at signal-to-noise ratio (S/N) ∼ 6, with F1000W ∼ 27 mag, and undetected in the NIRCam data gathered by the JWST Advanced Deep Extragalactic Survey (JADES), fainter than the 30.0–30.5 mag 5σ detection limits in individual bands, as well as in the MIDIS F560W ultradeep data (∼29 mag, 5σ). Analyzing the spectral energy distribution built with low-S/N (<5) measurements in individual optical-to-mid-infrared filters and higher-S/N (≳5) measurements in stacked NIRCam data, we discuss the possible nature of this red NIRCam-dark source using a battery of codes. We discard the possibility of Cerberus being a solar system body based on the <0.″016 proper motion in the 1 yr apart JADES and MIDIS observations. A substellar Galactic nature is deemed unlikely, given that the Cerberus’s relatively flat NIRCam-to-NIRCam and very red NIRCam-to-MIRI flux ratios are not consistent with any brown dwarf model. The extragalactic nature of Cerberus offers three possibilities: (1) a z ∼ 0.4 galaxy with strong emission from polycyclic aromatic hydrocarbons—the very low inferred stellar mass, M ⋆ = 105–106 M ⊙, makes this possibility highly improbable; (2) a dusty galaxy at z ∼ 4 with an inferred stellar mass M ⋆ ∼ 108 M ⊙; and (3) a galaxy with observational properties similar to those of the reddest little red dots discovered around z ∼ 7, but Cerberus lying at z ∼ 15, with the rest-frame optical dominated by emission from a dusty torus or a dusty starburst.

Extreme-emission-line galaxies in the MUSE Hubble Ultra Deep Field Survey

We aim to apply a methodology to build a sample of extreme-emission-line galaxies (EELGs) using integral field spectroscopy data. In this work, we followed the spectroscopic criteria corresponding to EELG selection and used the MUSE Hubble Ultra-Deep field survey, which includes the deepest spectroscopic survey ever performed. Objects in the primary (extended) sample were detected requiring a rest-frame equivalent width of EWo geqslant 300 leq EWo leq 300 ) in any of the emission lines of OII OIII or Halpha . A detailed closer inspection of the spectra of the candidates selected has been performed on a one-by-one basis in order to confirm their classification. For this sample, the line fluxes, physical properties, and chemical abundances of the EELGs have been derived, as well as their spatially resolved structure and kinematics. Four (five) of the galaxies in the primary (extended) sample, sim 57$&lt;!PCT!&gt;$ (sim 83$&lt;!PCT!&gt;$), were spatially resolved. Three (none) of them present a clear pattern compatible with rotation. We show how our entire EELG sample shares the same loci defined by high-redshift galaxies (z approx 6-8) for the mass-metallicity relation, illustrating their role as local analogs.

The MUSE Ultra Deep Field (MUDF). V. Characterizing the Mass–Metallicity Relation for Low-mass Galaxies at z ∼ 1–2

Using more than 100 galaxies in the MUSE Ultra Deep Field with spectroscopy from the Hubble Space Telescope’s (HST) Wide Field Camera 3 and the Very Large Telescope’s Multi Unit Spectroscopic Explorer, we extend the gas-phase mass–metallicity relation (MZR) at z ≈ 1–2 down to stellar masses of M ⋆ ≈ 107.5 M ⊙. The sample reaches 6 times lower in stellar mass and star formation rate (SFR) than previous HST studies at these redshifts, and we find that galaxy metallicities decrease to log(O/H) + 12 ≈ 7.8 ± 0.1 (15% solar) at log(M ⋆/M ⊙) ≈ 7.5, without evidence of a turnover in the shape of the MZR at low masses. We validate our strong-line metallicities using the direct method for sources with [O iii] λ4363 and [O iii] λ1666 detections, and find excellent agreement between the techniques. The [O iii] λ1666-based metallicities double existing measurements with a signal-to-noise ratio ≥ 5 for unlensed sources at z > 1, validating the strong-line calibrations up to z ∼ 2.5. We confirm that the MZR resides ∼0.3 dex lower in metallicity than local galaxies and is consistent with the fundamental metallicity relation if the low-mass slope varies with SFR. At lower redshifts (z ∼ 0.5) our sample reaches ∼0.5 dex lower in SFR than current calibrations and we find enhanced metallicities that are consistent with extrapolating the MZR to lower SFRs. Finally, we detect only an ∼0.1 dex difference in the metallicities of galaxies in groups versus isolated environments. These results are based on robust calibrations and reach the lowest masses and SFRs that are accessible with HST, providing a critical foundation for studies with the Webb and Roman Space Telescopes.

Cosmological prediction of the CSST Ultra Deep Field Type Ia supernova photometric survey

ABSTRACT Type Ia supernova (SN Ia) as a standard candle is an ideal tool to measure cosmic distance and expansion history of the Universe. Here, we investigate the SN Ia photometric measurement in the China Space Station Telescope Ultra Deep Field (CSST-UDF) survey, and study the constraint power on the cosmological parameters, such as the equation of state of dark energy. The CSST-UDF survey is expected to cover a 9 deg2 sky area in 2 yr with 250 s × 60 exposures for each band. The magnitude limit can reach i ≃ 26 AB mag for 5σ point source detection with a single exposure. We generate light-curve mock data for SNe Ia and different types of core-collapse SNe (CCSNe). sncosmo is chosen as the framework by utilizing the salt3 model to simulate SN Ia data. After selecting high-quality data and fitting the light curves, we derive the light-curve parameters and identify CCSNe as contamination, resulting in ∼2200 SNe with an $\sim\!\! 7{{\ \rm per\, cent}}$ CCSN contamination rate. We adopt a calibration method similar to Chauvenet’s criterion, and apply it to the distance modulus data to further reduce the contamination. We find that this method is effective and can suppress the contamination fraction to $\sim\!\! 3.5{{\ \rm per\, cent}}$ with 2012 SNe Ia and 73 CCSNe. In the cosmological fitting stage, we did not distinguish between SNe Ia and CCSNe. We find that the constraint accuracies on ΩM, ΩΛ, and w are about two times better than the current SN surveys, and they could be further improved by a factor of ∼1.4 if including the baryon acoustic oscillation data from the CSST spectroscopic wide-field galaxy survey.

The Next Generation Deep Extragalactic Exploratory Public (NGDEEP) Survey

We present the Next Generation Deep Extragalactic Exploratory Public (NGDEEP) Survey, a deep slitless spectroscopic and imaging Cycle 1 JWST treasury survey designed to constrain feedback mechanisms in low-mass galaxies across cosmic time. NGDEEP targets the Hubble Ultra Deep Field (HUDF) with NIRISS slitless spectroscopy ( flim,line,5σ≈1.2× 10−18 erg s−1 cm−2) to measure metallicities and star formation rates (SFRs) for low-mass galaxies through the peak of the cosmic SFR density (0.5 < z < 4). In parallel, NGDEEP targets the HUDF-Par2 parallel field with NIRCam ( mlim,5σ=30.6−30.9 ) to discover galaxies to z > 12, constraining the slope of the faint end of the rest-ultraviolet luminosity function. NGDEEP overlaps with the deepest HST Advanced Camera for Surveys optical imaging in the sky, F435W in the HUDF ( mlim,F435W=29.6 ) and F814W in HUDF-Par2 ( mlim,F814W=30 ), making this a premier HST+JWST deep field. As a treasury survey, NGDEEP data are public immediately, and we will rapidly release data products and catalogs in the spirit of previous deep-field initiatives. In this paper we present the NGDEEP survey design, summarize the science goals, and detail plans for the public release of NGDEEP reduced data products.

JADES: The production and escape of ionizing photons from faint Lyman-alpha emitters in the epoch of reionization

We present the properties of 17 faint Lyman-α emitting galaxies (LAEs) at z &gt; 5.8 from the JWST Advanced Deep Extragalactic Survey (JADES) spectroscopic data in the Hubble Ultra Deep Field/GOODS-S. These LAEs span a redshift range z ≈ 5.8 − 8.0 and a UV magnitude range MUV ≈ −17 to −20.6, with the Lyα equivalent width (EW) in the range ≈25 − 350 Å. The detection of other rest-optical emission lines in the spectra of these LAEs enables the determination of accurate systemic redshifts and Lyα velocity offsets, as well as the physical and chemical composition of their stars and interstellar media. These faint LAEs are consistent with metal-poor systems with high ionization parameters, similar to the general galaxy population at z &gt; 6. We measured an average ionizing photon production efficiency, log(ξion/erg−1 Hz) ≈ 25.57 across our LAEs, which does not evolve strongly with redshift. We report an anti-correlation between the Lyα escape fraction and the velocity offset from systemic redshift, consistent with model expectations. We further find that the strength and velocity offset of Lyα are neither correlated with galaxy spectroscopic properties nor with ξion. We find a decrease in Lyα escape fractions with redshift, indicative of decreasing sizes of ionized bubbles around LAEs at high redshifts. We used a range of galaxy properties to predict Lyman continuum escape fractions for our LAEs, finding that the ionizing photon output into the intergalactic medium from our LAEs remains roughly constant across the observed Lyα EW, showing a mild increase at fainter UV magnitudes and at higher redshifts. We derived correlations between the ionizing photon output from LAEs and their UV magnitudes, Lyα strengths and redshifts, which can be used to constrain the ionizing photon contribution of LAEs at z &gt; 6 towards cosmic reionization.

Insights into Galaxy Morphology and Star Formation: Unveiling Filamentary Structures around an Extreme Overdensity at z ∼ 1.5 Traced by [O ii] Emitters

We explore the morphological features and star formation activities of [O ii] emitters in the COSMOS UltraDeep field at z ∼ 1.5 using JWST NIRCam data from the COSMOS-Web survey and Subaru Hyper Suprime-Cam. We also report the discovery of large filamentary structures traced by [O ii] emitters surrounding an extremely overdense core with a galaxy number density ∼11× higher than the field average. These structures span over 50 cMpc, underscoring their large scale in the cosmic web at this epoch. After matching the stellar-mass distributions, the core galaxies show a higher frequency of disturbances (50% ± 9%) than those in the outskirts (41% ± 9%) and the field (21% ± 5%), indicative of more frequent mergers and interactions in the innermost ≲1.′5 region. Additionally, we observe that specific star formation rates are elevated in denser environments. A Kolmogorov–Smirnov test comparing the distribution of specific star formation rates of core and field galaxies yields a p-value of 0.02, suggesting an enhancement of star formation activity driven by the dense environment. Our findings underscore the environmental impact on galaxy evolution during a pivotal cosmic epoch and set the stage for further investigation with the increasing larger data from upcoming surveys.

Galaxy spin direction asymmetry in JWST deep fields

Abstract The unprecedented imaging power of JWST provides new abilities to observe the shapes of objects in the early Universe in a way that has not been possible before. Recently, JWST acquired a deep field image inside the same field imaged in the past as the HST Ultra Deep Field. Computer-based quantitative analysis of spiral galaxies in that field shows that among 34 galaxies for which their rotation of direction can be determined by the shapes of the arms, 24 rotate clockwise, and just 10 rotate counterclockwise. The one-tailed binomial distribution probability to have asymmetry equal or stronger than the observed asymmetry by chance is ∼0.012. While the analysis is limited by the small size of the data, the observed asymmetry is aligned with all relevant previous large-scale analyses from all premier digital sky surveys, all show a higher number of galaxies rotating clockwise in that part of the sky, and the magnitude of the asymmetry increases as the redshift gets higher. This paper also provides data and analysis to reproduce previous experiments suggesting that the distribution of galaxy rotation in the Universe is random, to show that the exact same data used in these studies in fact show non-random distribution, and in excellent agreement with the results shown here. These findings reinforce consideration of the possibility that the directions of rotation of spiral galaxies as observed from Earth are not necessarily randomly distributed. The explanation can be related to the large-scale structure of the Universe, but can also be related to a possible anomaly in the physics of galaxy rotation.

NGDEEP Epoch 1: Spatially Resolved Hα Observations of Disk and Bulge Growth in Star-forming Galaxies at z ∼ 0.6–2.2 from JWST NIRISS Slitless Spectroscopy

We study the Hα equivalent width (EW(Hα)) maps of 19 galaxies at 0.6 < z < 2.2 in the Hubble Ultra Deep Field using NIRISS slitless spectroscopy as part of the Next Generation Deep Extragalactic Exploratory Public Survey. Our galaxies mostly lie on the star formation main sequence with stellar masses between 109 and 1011 M ⊙, characterized as “typical” star-forming galaxies at these redshifts. Leveraging deep Hubble Space Telescope and JWST images, spanning 0.4–4.8 μm, we perform spatially resolved fitting of the spectral energy distributions for these galaxies and construct specific star formation rate (sSFR) and stellar-mass-weighted age maps with a spatial resolution of ∼1 kpc. The pixel-to-pixel EW(Hα) increases with increasing sSFR and with decreasing age. The average trends are slightly different from the relations derived from integrated fluxes of galaxies from the literature, suggesting complex evolutionary trends within galaxies. We quantify the radial profiles of EW(Hα), sSFR, and age. The majority (84%) of galaxies show positive EW(Hα) gradients, in line with the inside-out quenching scenario. A few galaxies (16%) show inverse (and flat) EW(Hα) gradients, possibly due to merging or starbursts. We compare the distributions of EW(Hα) and sSFR to star formation history (SFH) models as a function of galactocentric radius. We argue that the central regions of galaxies have experienced at least one rapid star formation episode, which leads to the formation of the bulge, while their outer regions (e.g., disks) grow via more smoothly varying SFHs. These results demonstrate the ability to study resolved star formation in distant galaxies with JWST NIRISS.

An optimal ALMA image of the Hubble Ultra Deep Field in the era of JWST: obscured star formation and the cosmic far-infrared background

ABSTRACT We combine archival ALMA data targeting the Hubble Ultra Deep Field (HUDF) to produce the deepest currently attainable 1-mm maps of this key region. Our deepest map covers 4.2 arcmin2, with a beamsize of 1.49 arcsec $\, {\times }\, 1.07\,$ arcsec at an effective frequency of 243 GHz (1.23 mm). It reaches an rms of 4.6 μJy beam$^{-1}$, with 1.5 arcmin2 below 9.0 μJy beam−1, an improvement of ${\gt }\,$5 per cent (and up to 50 per cent in some regions) over the best previous map. We also make a wider, shallower map, covering 25.4 arcmin2. We detect 45 galaxies in the deep map down to 3.6$\sigma$, 10 more than previously detected, and 39 of these galaxies have JWST counterparts. A stacking analysis on the positions of ALMA-undetected JWST galaxies yields 10 per cent more signal compared to previous stacking analyses, and we find that detected sources plus stacking contribute (10.0 ${\pm }$ 0.5) Jy deg−2 to the cosmic infrared background (CIB) at 1.23 mm. Although this is short of the (uncertain) background level of about 20 Jy deg−2, we show that our measurement is consistent with the background if the HUDF is a mild (${\sim }\, 2\sigma$) negative CIB fluctuation, and that the contribution from faint undetected objects is small and converging. This suggests that JWST has detected essentially all of the galaxies that contribute to the CIB, as anticipated from the strong correlation between galaxy stellar mass and obscured star formation.

Constraints on the Faint End of the Galaxy Stellar Mass Function at z ≃ 4–8 from Deep JWST Data

We analyze a sample of 3300 galaxies between redshifts z ≃ 3.5 and z ≃ 8.5 selected from James Webb Space Telescope (JWST) images in the Hubble Ultra Deep Field and UKIDSS Ultra Deep Survey field, including objects with stellar masses as low as ≃108 M ⊙ up to z ≃ 8. The depth and wavelength coverage of the JWST data allows us, for the first time, to derive robust stellar masses for such high-z, low stellar mass galaxies on an individual basis. We compute the galaxy stellar mass function, after complementing our sample with ancillary data from CANDELS to constrain the GMSF at high stellar masses ( M>M* ). Our results show a steepening of the low stellar mass end slope (α) with redshift, with α = −1.61 ± 0.05 at z ≃ 4 and α = −1.98 ± 0.14 at z ≃ 7. We also observe an evolution of the normalization ϕ * from z ≃ 7 to z ≃ 4, with ϕz≃4*/ϕz≃7*=130−50+210 . Our study incorporates a novel method for the estimation of the Eddington bias, which takes into account its possible dependence both on stellar mass and redshift, while allowing for skewness in the error distribution. We finally compute the resulting cosmic stellar mass density and find a flatter evolution with redshift than previous studies.