We present a spatially resolved analysis of four star-forming galaxies at z = 4.44-5.64 using data from the JWST Public Release Imaging for Extragalactic Research (PRIMER) and ALMA-[C II] Resolved ISm in STar-forming galaxies with ALma (CRISTAL) surveys to probe the stellar and interstellar medium properties on the sub-kpc scale. In the 1-5 mu m JWST NIRCam imaging we find that the galaxies are composed of multiple clumps (between 2 and similar to 8) separated by similar or equal to 5kpc, with comparable morphologies and sizes in the rest-frame ultraviolet (UV) and optical. Using BAGPIPES to perform pixel-by-pixel spectral energy distribution (SED) fitting to the JWST data, we show that the star formation rate (SFR) (similar or equal to 25M(circle dot)yr(-1)) and stellar mass (log10(M star/M-circle dot) similar or equal to 9.5) derived from the resolved analysis are in close (less than or similar to 0.3dex) agreement with those obtained by fitting the integrated photometry. In contrast to studies of lower mass sources, we thus find a reduced impact of outshining of the older (more massive) stellar populations in these normal z similar or equal to 5 galaxies. Our JWST analysis recovers bluer rest-frame UV slopes (beta similar or equal to -2.1) and younger ages (similar or equal to 100Myr) than archival values. We find that the dust continuum from ALMA-CRISTAL seen in two of these galaxies correlates, as expected, with regions of redder rest-frame UV slopes and the SED-derived AV, as well as the peak in the stellar mass map. We compute the resolved IRX-beta relation, showing that the IRX is consistent with the local starburst attenuation curve and further demonstrating the presence of an inhomogeneous dust distribution within the galaxies. A comparison of the CRISTAL sources to those from the FirstLight zoom-in simulation of galaxies with the same M star and SFR reveals similar age and colour gradients, suggesting that major mergers may be important in the formation of clumpy galaxies at this epoch.

The ALMA [CII] Resolved Ism in STar-forming gALaxies (CRISTAL) survey is a Cycle 8 ALMA Large Programme that studies the cold gas component of high-redshift galaxies. Its sub-arcsecond resolution observations are key to disentangling physical mechanisms that shape galaxies during cosmic dawn. In this paper, we explore the morphology and kinematics of the cold gas, star-forming, and stellar components in the star-forming main-sequence galaxy CRISTAL-05/HZ3, at z = 5.54. Our analysis includes 0.3" spatial resolution ( 2 kpc) ALMA observations of the [CII] line. While CRISTAL-05 was previously classified as a single source, our observations reveal that the system is a close interacting pair surrounded by an extended component of carbon-enriched gas. This is imprinted in the disturbed elongated [CII] morphology and the separation of the two components in the position-velocity diagram ( 100 km/s). The central region is composed of two components, named C05-NW and C05-SE, with the former being the dominant one. A significant fraction of the [CII] arises beyond the close pair up to 10 kpc, while the regions forming new massive stars and the stellar component seem compact (r_[CII] 4 r_UV), as traced by rest-frame UV and optical imaging obtained with the Hubble Space Telescope and the James Webb Space Telescope. Our kinematic model, using the DYSMALpy software, yields a minor contribution of dark matter of C05-NW within a radius of 2x Reff. Finally, we explore the resolved [CII]/FIR ratios as a proxy for shock-heating produced by this merger. We argue that the extended [CII] emission is mainly caused by the merger, which could not be discerned with lower-resolution observations. Our work emphasizes the need for high-resolution observations to fully characterize the dynamic stages of infant galaxies and the physical mechanisms that drive the metal enrichment of the circumgalactic medium.

Context. One of the surprising early findings with JWST has been the discovery of a strong “roll-over” or a softening of the absorption edge of Lyα in a large number of galaxies at z ≳ 6, in addition to systematic offsets from photometric redshift estimates and fundamental galaxy scaling relations. This has been interpreted as strong cumulative damped Lyα absorption (DLA) wings from high column densities of neutral atomic hydrogen (H I), signifying major gas accretion events in the formation of these galaxies. Aims. To explore this new phenomenon systematically, we assembled the JWST/NIRSpec PRImordial gas Mass AssembLy (PRIMAL) legacy survey of 584 galaxies at z = 5.0 − 13.4, designed to study the physical properties and gas in and around galaxies during the reionization epoch. Methods. We characterized this benchmark sample in full and spectroscopically derived the galaxy redshifts, metallicities, star formation rates, and ultraviolet (UV) slopes. We defined a new diagnostic, the Lyα damping parameter DLyα, to measure and quantify the net effect of Lyα emission strength, the H I fraction in the intergalactic medium, or the local H I column density for each source. The JWST-PRIMAL survey is based on the spectroscopic DAWN JWST Archive (DJA-Spec). We describe DJA-Spec in this paper, detailing the reduction methods, the post-processing steps, and basic analysis tools. All the software, reduced spectra, and spectroscopically derived quantities and catalogs are made publicly available in dedicated repositories. Results. We find that the fraction of galaxies showing strong integrated DLAs with NHI > 1021 cm−2 only increases slightly from ≈60% at z ≈ 6 up to ≈65 − 90% at z > 8. Similarly, the prevalence and prominence of Lyα emission is found to increase with decreasing redshift, in qualitative agreement with previous observational results. Strong Lyα emitters (LAEs) are predominantly found to be associated with low-metallicity and UV faint galaxies. By contrast, strong DLAs are observed in galaxies with a variety of intrinsic physical properties, but predominantly at high redshifts and low metallicities. Conclusions. Our results indicate that strong DLAs likely reflect a particular early assembly phase of reionization-era galaxies, at which point they are largely dominated by pristine H I gas accretion. At z = 8 − 10, this gas gradually cools and forms into stars that ionize their local surroundings, forming large ionized bubbles and producing strong observed Lyα emission at z < 8.

Context. One of the surprising early findings with JWST has been the discovery of a strong "roll-over" or a softening of the absorption edge of Ly alpha in a large number of galaxies at z greater than or similar to 6, in addition to systematic offsets from photometric redshift estimates and fundamental galaxy scaling relations. This has been interpreted as strong cumulative damped Ly alpha absorption (DLA) wings from high column densities of neutral atomic hydrogen (H I), signifying major gas accretion events in the formation of these galaxies. Aims. To explore this new phenomenon systematically, we assembled the JWST/NIRSpec PRImordial gas Mass AssembLy (PRIMAL) legacy survey of 584 galaxies at z = 5.0 - 13.4, designed to study the physical properties and gas in and around galaxies during the reionization epoch. Methods. We characterized this benchmark sample in full and spectroscopically derived the galaxy redshifts, metallicities, star formation rates, and ultraviolet (UV) slopes. We defined a new diagnostic, the Ly alpha damping parameter D-Ly alpha, to measure and quantify the net effect of Ly alpha emission strength, the H I fraction in the intergalactic medium, or the local H I column density for each source. The JWST-PRIMAL survey is based on the spectroscopic DAWN JWST Archive (DJA-Spec). We describe DJA-Spec in this paper, detailing the reduction methods, the post-processing steps, and basic analysis tools. All the software, reduced spectra, and spectroscopically derived quantities and catalogs are made publicly available in dedicated repositories. Results. We find that the fraction of galaxies showing strong integrated DLAs with N-HI > 10(21) cm(-2) only increases slightly from approximate to 60% at z approximate to 6 up to approximate to 65 - 90% at z > 8. Similarly, the prevalence and prominence of Ly alpha emission is found to increase with decreasing redshift, in qualitative agreement with previous observational results. Strong Ly alpha emitters (LAEs) are predominantly found to be associated with low-metallicity and UV faint galaxies. By contrast, strong DLAs are observed in galaxies with a variety of intrinsic physical properties, but predominantly at high redshifts and low metallicities. Conclusions. Our results indicate that strong DLAs likely reflect a particular early assembly phase of reionization-era galaxies, at which point they are largely dominated by pristine H I gas accretion. At z = 8 - 10, this gas gradually cools and forms into stars that ionize their local surroundings, forming large ionized bubbles and producing strong observed Ly alpha emission at z < 8.

One of the surprising early findings with JWST has been the discovery of a strong "roll-over" or a softening of the absorption edge of Ly$\alpha$ in a large number of galaxies at ($z\gtrsim 6$), in addition to systematic offsets from photometric redshift estimates and fundamental galaxy scaling relations. This has been interpreted as damped Ly$\alpha$ absorption (DLA) wings from high column densities of neutral atomic hydrogen (HI), signifying major gas accretion events in the formation of these galaxies. To explore this new phenomenon systematically, we assemble the JWST/NIRSpec PRImordial gas Mass AssembLy (PRIMAL) legacy survey of 494 galaxies at $z=5.5-13.4$. We characterize this benchmark sample in full and spectroscopically derive the galaxy redshifts, metallicities, star-formation rates, and ultraviolet slopes. We define a new diagnostic, the Ly$\alpha$ damping parameter $D_{\rm Ly\alpha}$ to measure and quantify the Ly$\alpha$ emission strength, HI fraction in the IGM, or local HI column density for each source. The JWST-PRIMAL survey is based on the spectroscopic DAWN JWST Archive (DJA-Spec). All the software, reduced spectra, and spectroscopically derived quantities and catalogs are made publicly available in dedicated repositories. The fraction of strong galaxy DLAs are found to be in the range $65-95\%$ at $z>5.5$. The fraction of strong Ly$\alpha$ emitters (LAEs) is found to increase with decreasing redshift, in qualitative agreement with previous observational results, and are predominantly associated with low-metallicity and UV faint galaxies. By contrast, strong DLAs are observed in galaxies with a variety of intrinsic physical properties. Our results indicate that strong DLAs likely reflect a particular early assembly phase of reionization-era galaxies, at which point they are largely dominated by pristine HI gas accretion. [abridged]

We present new lambda(rest) = 77 mu m dust continuum observations from the Atacama Large Millimeter/submillimeter Array of HZ10 (CRISTAL-22). This dusty main sequence galaxy at z = 5.66 was observed as part of the [CII] Resolved Ism in STar-forming Alma Large program (CRISTAL). The high angular resolution of the ALMA Band 7 and new Band 9 data (similar to 0 ''.4) reveals the complex structure of HZ10, which comprises two main components (HZ10-C and HZ10-W), along with a bridge-like dusty emission between them (i.e., "the bridge"). Using a modified blackbody function to model the dust spectral energy distribution (SED), we constrained the physical conditions of the interstellar medium (ISM) and its variations among the different components identified in HZ10. We find that HZ10-W (the more UV-obscured component) has an SED dust temperature of T-SED similar to 51.2 +/- 13.1 K; this was found to be similar to 5 K higher (which is statistically insignificant; i.e., less than 1 sigma) than that of the central component and previous global estimations for HZ10. Our new ALMA data allow us to reduce the uncertainties of global T-SED measurements by a factor of similar to 2.3, compared to previous studies. The HZ10 components have [CII]-to-far-infrared (FIR) luminosity ratios and FIR surface densities values that are consistent with local starburst galaxies. However, HZ10-W shows a lower [CII]/FIR ratio compared to the other two components (albeit still within the uncertainties), which may suggest a harder radiation field destroying polycyclic aromatic hydrocarbon associated with [CII] emission (e.g., active galactic nuclei or young stellar populations). While HZ10-C appears to follow the tight IRX-beta(UV) relation seen in local UV-selected starburst galaxies and high-z star-forming galaxies, we find that both HZ10-W and the bridge depart from this relation and are well described by dust-screen models with holes in front of a hard UV radiation field. This suggests that the UV emission, which is likely coming from young stellar populations, is strongly attenuated in the "dustier" components of the HZ10 system.

Context. Determining when the first galaxies formed remains an outstanding goal of modern observational astronomy. Theory and current stellar population models imply that the first galaxies formed at least at z = 14 15. But to date, only one galaxy at z > 13 (GS-z13-0) has been spectroscopically confirmed. Aims. The galaxy `HD1' was recently proposed to be a z similar to 13:27 galaxy based on its potential Lyman break and tentative [O iii] 88 mu m detection with ALMA. We hereby aim to test this scenario with new ALMA Band 4 observations of what would be the [C II] 158 mu m emission if HD1 is at z similar to 13:27. Methods. We carefully analyse the new ALMA Band 4 observations and re-analyse the existing ALMA Band 6 data on the source to determine the proposed redshift. Results. We find a tentative 4 sigma feature in the Band 4 data that is spatially o ffset by 1:'' 7 and spectrally o ffset by 190 km s(-1) from the previously reported 3.8 sigma `[O III] 88 mu m' feature. Through various statistical tests, we demonstrate that these tentative features are fully consistent with both being random noise features. Conclusions. We conclude that we are more likely to be recovering noise features than both [O III] 88 mu m and [C II] 158 mu m emission from a source at z similar to 13 :27. Although we find no credible evidence of a z similar to 13 :27 galaxy, we cannot entirely rule out this scenario. Non-detections are also possible for a z similar to 13 source with a low interstellar gas-phase metallicity or ionisation parameter and/or high gas density. Moreover, the new continuum and line upper limits provide no strong evidence for or against a lower-redshift scenario. Determining where and exactly what type of galaxy HD1 is, will now likely require JWST /NIRSpec spectroscopy.

The chemical enrichment of dust and metals are vital processes in constraining the star formation history of the universe. Previously, the dust masses of high-redshift star-forming galaxies have been determined through their far-infrared continuum, however, equivalent, and potentially simpler, approaches to determining the metal masses have yet to be explored at $z\gtrsim 2$. Here, we present a new method of inferring the metal mass in the interstellar medium (ISM) of galaxies out to $z\approx 8$, using the far-infrared [CII]$-158\mu$m emission line as a proxy. We calibrated the [CII]-to-$M_{\rm Z,ISM}$ conversion factor based on a benchmark observational sample at $z\approx 0$, in addition to gamma-ray burst sightlines at $z>2$ and cosmological hydrodynamical simulations of galaxies at $z\approx 0$ and $z\approx 6$. We found a universal scaling across redshifts of $\log (M_{\rm Z,ISM}/M_\odot) = \log (L_{\rm [CII]}/L_\odot) - 0.45,$ with a 0.4 dex scatter, which is constant over more than two orders of magnitude in metallicity. We applied this scaling to recent surveys for [CII] in galaxies at $z\gtrsim 2$ and determined the fraction of metals retained in the gas-phase ISM, $M_{\rm Z,ISM} / M_\star$, as a function of redshift showing that an increasing fraction of metals reside in the ISM of galaxies at higher redshifts. We place further constraints on the cosmic metal mass density in the ISM ($\Omega_{\rm Z,ISM}$) at $z\approx 5$ and $\approx 7$, yielding $\Omega_{\rm Z,ISM} = 6.6^{+13}_{-4.3}\times 10^{-7}\,M_\odot\, {\rm Mpc}^{-3}$ ($z\approx 5$) and $\Omega_{\rm Z,ISM} = 2.0^{+3.5}_{-1.3}\times 10^{-7}\,M_\odot\, {\rm Mpc}^{-3}$ ($z\approx 7$). These results are consistent with the expected metal yields from the integrated star formation history at the respective redshifts. This suggests that the majority of metals produced at $z\gtrsim 5$ are confined to the ISM of galaxies.

Determining when the first galaxies formed remains an outstanding goal of modern observational astronomy. Theory and current stellar population models imply that the first galaxies formed at least at $z = 14-15$. But to date, only one galaxy at $z>13$ (GS-z13-0) has been spectroscopically confirmed.. The galaxy `HD1' was recently proposed to be a z=13.27 galaxy based on its potential Lyman break and tentative [O III] 88 {\mu}m detection with ALMA. We hereby aim to test this scenario with new ALMA Band 4, DDT observations of what would be the [C II] 158 {\mu}m emission, if HD1 is at z$\sim$13.27. We carefully analyse the new ALMA Band 4 observations and re-analyse the existing ALMA Band 6 data on the source to determine the proposed redshift. We find a tentative $4\sigma$ feature in the Band 4 data that is spatially offset by 1.7"and spectrally offset by 190 km s-1 from the previously-reported $3.8\sigma$ `[O III] 88 {\mu}m' feature. Through various statistical tests, we demonstrate that these tentative features are fully consistent with both being random noise features. We conclude that we are more likely to be recovering noise features than both [O III] and [C II] emission from a source at $z\sim 13.27$. Although we find no credible evidence of a $z\sim 13.27$ galaxy, we cannot entirely rule out this scenario. Non-detections are also possible for a $z\sim 13$ source with a low interstellar gas-phase metallicity or ionisation parameter and/or high gas density. Determining where and exactly what type of galaxy HD1 is, will now likely require JWST/NIRSpec spectroscopy.

We present the first detection of the [N ii] 122 µ m and [O iii] 52 µ m lines for a reionisation-epoch galaxy. Based on these lines and previous [C ii] 158 µ m and [O iii] 88 µ m measurements, we estimate an electron density of (cid:46) 500 cm − 3 and a gas-phase metallicity 𝑍 / 𝑍 (cid:12) ∼ 1 . 1 ± 0 . 2 for A1689-zD1, a gravitationally-lensed, dusty galaxy at 𝑧 = 7 . 133. Other measurements or indicators of metallicity so far in galaxy ISMs at 𝑧 (cid:38) 6 are typically an order of magnitude lower than this. The unusually high metallicity makes A1689-zD1 inconsistent with the fundamental metallicity relation, although there is likely significant dust obscuration of the stellar mass, which may partly resolve the inconsistency. Given a solar metallicity, the dust-to-metals ratio is a factor of several lower than expected, hinting that galaxies beyond 𝑧 ∼ 7 may have lower dust formation efficiency. Finally, the inferred nitrogen enrichment compared to oxygen, on which the metallicity measurement depends, indicates that star-formation in the system is older than about 250 Myr, pushing the beginnings of this galaxy to 𝑧 > 10.