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We present new free-form and hybrid mass reconstructions of the galaxy cluster lens MACS J0416.1 |$-$| 2403 at |$z=0.396$| using the lens inversion method GRALE. The reconstructions use 237 spectroscopically confirmed multiple images from Bergamini et al. (2023) as the main input. Our primary model reconstructs images to a positional accuracy of 0.191 arcsec, thus representing one of the most precise reconstructions of this lens to date. Our models find broad agreement with previous reconstructions, and identify two |$\sim 10^{12}\, {\rm M}_{\odot }$| light-unaffiliated substructures. We focus on two highly magnified arcs: Spock and Mothra. Our model features a unique critical curve structure around the Spock arc with 2 crossings. This structure enables sufficient magnification across this arc to potentially explain the large number of transients as microlensing events of supergiant stars. Additionally, we develop a model of the millilens substructure expected to be magnifying Mothra, which may be a binary pair of supergiants with |$\mu \sim 6000$|⁠. This model accounts for flexibility in the millilens position while preserving the observed flux and minimizing image position displacements along the Mothra arc. We constrain the millilens mass and core radius to |$\lesssim 10^6 {\rm M}_{\odot }$| and |$\lesssim 17$|  pc, respectively, which would render it one of the smallest and most compact substructures constrained by lensing. If the millilens is dominated by wave dark matter, the axion mass is constrained to be |$\lesssim 3.0 \times 10^{-21}$|  eV. Further monitoring of this lens with JWST will uncover more transients, permitting tighter constraints on the structure surrounding these two arcs. [ABSTRACT FROM AUTHOR]

The current paradigm for the co-evolution of galaxies and their supermassive black holes postulates that dust-obscured active galactic nuclei (AGNs) represent a transitional phase towards a more luminous and unobscured state. However, our understanding of dusty AGNs and their host galaxies at early cosmic times is inadequate due to observational limitations. Here, we present JWST observations of CID-931, an X-ray-detected AGN at a spectroscopic redshift of |$z_{\rm spec}=4.91$|⁠. Multiband NIRCam imaging from the COSMOS-Web program reveals an unresolved red core, similar to JWST-discovered dusty AGNs. Strikingly, the red core is surrounded by at least eight massive star-forming clumps spread over |${1{^{\prime \prime}_{.}}6} \approx 10\,\,{\rm kpc}$|⁠ , each of which has a stellar mass of |$10^9$| – |$10^{10}\, M_{\odot }$| and a radius of |$\sim$| 0.1–1 kpc. The whole system amounts to |$10^{11}\, M_{\odot }$| in stellar mass, higher than typical star-forming galaxies at the same epoch. In this system, gas inflows and/or complex merger events may trigger clump formation and AGN activity, thus leading to the rapid formation of a massive galaxy hosting a supermassive black hole. Future follow-up observations will provide new insights into the evolution of the galaxy–black hole relationship during such transitional phases in the early universe. [ABSTRACT FROM AUTHOR]

Photometric redshifts are widely used in studies of dusty star-forming galaxies (DSFGs), but catastrophic photo-z failure can undermine all redshift-dependent results. Here we report the spectroscopic redshift confirmation of COSBO-7, a strongly lensed DSFG in the COSMOS-PRIMER field. Recently, a photometric redshift solution of z ≳ 7.0 was reported for COSBO-7 based on ten bands of James Webb Space Telescope (JWST) NIRCam and MIRI imaging data. This z value was favored by four independent spectral energy distribution (SED) fitting codes, and the result provided an appealing candidate for the most distant massive DSFG known to date. This photo-z solution was also supported by a single line detection in Atacama Large Millimeter Array (ALMA) Band 3 consistent with CO(7–6) at z = 7.46. However, our new ALMA observations robustly detect two lines in Band 6 identified as CO(7–6) and [CI](2–1) at zspec = 2.625, and thus the Band 3 line as CO(3–2). These three robust line detections decidedly place COSBO-7 at z = 2.625, refuting the photo-z solution. We derive physical parameters by fitting near-infrared(NIR)-to-millimeter(mm) photometry and lens modeling, revealing that COSBO-7 is a main sequence galaxy. We examine possible reasons for this photo-z failure and attribute it to (1) the likely underestimation of photometric uncertainties at 0.9 μm and 1.15 μm; and (2) the lack of photometry at wavelengths beyond 20 μm. Notably, we recover a bona fide zphot ∼ 2.3 by including the existing MIPS 24 μm photometry, demonstrating the critical importance of mid-infrared (MIR) data in bolstering photo-z measurements. This work highlights a common challenge in modeling the SEDs of DSFGs, and provides a cautionary tale regarding the reliability of photometric redshifts as well as pseudo-spectroscopic redshifts based on single line detection. [ABSTRACT FROM AUTHOR]

We present the first spectroscopic ALMA follow-up for a pilot sample of nine radio-selected near-IR-dark galaxies in the COSMOS field. These sources were initially selected as radio-detected sources (S3 GHz > 12.65 μJy) without an optical or near-IR (NIR) counterpart in the COSMOS2015 catalog (Ks ≳ 24.7 mag), and just three of them were subsequently detected in the deeper COSMOS2020. Several studies highlighted that this selection could provide a population of highly dust-obscured, massive, and star-bursting galaxies. With these new ALMA observations, we assess the spectroscopic redshifts of this pilot sample of sources and improve the quality of the physical properties estimated through SED-fitting. Moreover, we measure the quantity of molecular gas inside these galaxies and forecast their potential evolutionary path, finding that the radio-selected NIR-dark galaxies might likely represent a population of high-z progenitors of the massive and passive galaxies that were discovered at z ∼ 3. Finally, we present some initial constraints on the kinematics of the interstellar medium within the analyzed galaxies, reporting a high fraction (∼55%) of double-peaked lines that can be interpreted as the signature of a rotating structure in our targets or as the presence of major mergers in our sample. The results we present here show the scientific potential of (sub)mm observations for this elusive population of galaxies and highlight the potential contribution of these sources to the evolution of the massive and passive galaxies at high z. [ABSTRACT FROM AUTHOR]

The morphology of galaxies is shaped by stellar activity, feedback, gas and dust properties, and interactions with surroundings, and can therefore provide insight into these processes. In this paper, we study the spatial offsets between stellar and interstellar medium emission in a sample of 54 main-sequence star-forming galaxies at z ∼ 4–6 observed with the Atacama Large Millimeter/submillimeter Array (ALMA), and drawn from the ALMA Large Program to INvestigate C+ at Early times (ALPINE). We find no significant spatial offset for the majority (∼70 per cent) of galaxies in the sample among any combination of [C  ii ], far-infrared continuum, optical, and ultraviolet emission. However, a fraction of the sample (∼30 per cent) shows offsets larger than the median by more than 3σ significance (compared to the uncertainty on the offsets), especially between [C  ii ] and ultraviolet emission. We find that these significant offsets are of the order of ∼0.5–0.7 arcsec, corresponding to ∼3.5–4.5 kiloparsecs. The offsets could be caused by a complex dust geometry, strong feedback from stars and active galactic nuclei, large-scale gas inflow and outflow, or a combination of these phenomena. However, our current analysis does not definitively constrain the origin. Future, higher resolution ALMA and JWST observations may help resolve the ambiguity. Regardless, since there exist at least some galaxies that display such large offsets, galaxy models and spectral energy distribution fitting codes cannot assume co-spatial emission in all main-sequence galaxies, and must take into account that the observed emission across wavelengths may be spatially segregated. [ABSTRACT FROM AUTHOR]

We report the identification of 64 new candidates of compact galaxies, potentially hosting faint quasars with bolometric luminosities of Lbol = 1043–1046 erg s−1, residing in the reionization epoch within the redshift range of 6 ≲ z ≲ 8. These candidates were selected by harnessing the rich multiband datasets provided by the emerging JWST-driven extragalactic surveys, focusing on COSMOS-Web, as well as JADES, UNCOVER, CEERS, and PRIMER. Our search strategy includes two stages: applying stringent photometric cuts to catalog-level data and detailed spectral energy distribution fitting. These techniques effectively isolate the quasar candidates while mitigating contamination from low-redshift interlopers, such as brown dwarfs and nearby galaxies. The selected candidates indicate physical traits compatible with low-luminosity active galactic nuclei, likely hosting ≈105–107M⊙ supermassive black holes (SMBHs) living in galaxies with stellar masses of ≈108–1010M⊙. The SMBHs selected in this study, on average, exhibit an elevated mass compared to their hosts, with the mass ratio distribution slightly higher than those of galaxies in the local Universe. As with other high-z studies, this is at least in part due to the selection method for these quasars. An extensive Monte Carlo analysis provides compelling evidence that heavy black hole seeds from the direct collapse scenario appear to be the preferred pathway to mature this specific subset of SMBHs by z ≈ 7. Notably, most of the selected candidates might have emerged from seeds with masses of ∼105M⊙, assuming a thin disk accretion with an average Eddington ratio of fEdd = 0.6 ± 0.3 and a radiative efficiency of ϵ = 0.2 ± 0.1. This work underscores the significance of further spectroscopic observations, as the quasar candidates presented here offer exceptional opportunities to delve into the nature of the earliest galaxies and SMBHs that formed during cosmic infancy. [ABSTRACT FROM AUTHOR]

Understanding the star formation rate (SFR) variability and how it depends on physical properties of galaxies is important for developing and testing the theory of galaxy formation. We investigate how statistical measurements of the extragalactic background light (EBL) can shed light on this topic and complement traditional methods based on observations of individual galaxies. Using semi-empirical models of galaxy evolution and SFR indicators sensitive to different star formation time-scales (e.g. H α and ultraviolet continuum luminosities), we show that the SFR variability, quantified by the joint probability distribution of the SFR indicators (i.e. the bivariate conditional luminosity function), can be characterized as a function of galaxy mass and redshift through the cross-correlation between deep, near-infrared maps of the EBL and galaxy distributions. As an example, we consider combining upcoming SPHEREx maps of the EBL with galaxy samples from Rubin Observatory Legacy Survey of Space and Time. We demonstrate that their cross-correlation over a sky fraction of f sky ∼ 0.5 can constrain the joint SFR indicator distribution at high significance up to z ∼ 2.5 for mass-complete samples of galaxies down to |$M_{*}\sim 10^9\, {\rm M}_{\odot }$|⁠. These constraints not only allow models of different SFR variability to be distinguished, but also provide unique opportunities to investigate physical mechanisms that require large number statistics such as environmental effects. The cross-correlations investigated illustrate the power of combining cosmological surveys to extract information inaccessible from each data set alone, while the large galaxy populations probed capture ensemble-averaged properties beyond the reach of targeted observations towards individual galaxies. [ABSTRACT FROM AUTHOR]

We investigate the strong-lensing cluster Abell 370 (A370) using a wide Integral Field Unit (IFU) spectroscopic mosaic from the Multi-Unit Spectroscopic Explorer (MUSE). IFU spectroscopy provides significant insight into the structure and mass content of galaxy clusters, yet IFU-based cluster studies focus almost exclusively on the central Einstein-radius region. Covering over 14 arcmin2, the new MUSE mosaic extends significantly beyond the A370 Einstein radius, providing, for the first time, a detailed look at the cluster outskirts. Combining these data with wide-field, multi-band Hubble Space Telescope (HST) imaging from the BUFFALO project, we analyse the distribution of objects within the cluster and along the line of sight. Identifying 416 cluster galaxies, we use kinematics to trace the radial mass profile of the halo, providing a mass estimate independent from the lens model. We also measure radially averaged properties of the cluster members, tracking their evolution as a function of infall. Thanks to the high spatial resolution of our data, we identify six cluster members acting as galaxy–galaxy lenses, which constrain localized mass distributions beyond the Einstein radius. Finally, taking advantage of MUSE's 3D capabilities, we detect and analyse multiple spatially extended overdensities outside of the cluster that influence lensing-derived halo mass estimates. We stress that much of this work is only possible thanks to the robust, extended IFU coverage, highlighting its importance even in less optically dense cluster regions. Overall, this work showcases the power of combining HST  + MUSE, and serves as the initial step towards a larger and wider program targeting several clusters. [ABSTRACT FROM AUTHOR]

A multiwavelength study of galaxies is important to understand their formation and evolution. Only in the recent past, thanks to the Atacama Large (Sub) Millimeter Array (ALMA), were we able to study the far-infrared (IR) properties of galaxies at high redshifts. In this article, we summarize recent research highlights and their significance to our understanding of early galaxy evolution from the ALPINE survey, a large program with ALMA to observe the dust continuum and 158 μ m C + emission of normal star-forming galaxies at z = 4–6. Combined with ancillary data at UV through near-IR wavelengths, ALPINE provides the currently largest multiwavelength sample of post-reionization galaxies and has advanced our understanding of (i) the demographics of C + emission; (ii) the relation of star formation and C + emission; (iii) the gas content; (iv) outflows and enrichment of the intergalactic medium; and (v) the kinematics, emergence of disks, and merger rates in galaxies at z > 4 . ALPINE builds the basis for more detailed measurements with the next generation of telescopes, and places itself as an important post-reionization baseline sample to allow a continuous study of galaxies over 13 billion years of cosmic time. [ABSTRACT FROM AUTHOR]

The infrared (IR) spectral energy distributions (SEDs) of main-sequence galaxies in the early Universe (z > 4) is currently unconstrained as IR continuum observations are time-consuming and not feasible for large samples. We present Atacama Large Millimetre Array Band 8 observations of four main-sequence galaxies at z ∼ 5.5 to study their IR SED shape in detail. Our continuum data (rest-frame 110  |$\rm \mu m$|⁠ , close to the peak of IR emission) allows us to constrain luminosity-weighted dust temperatures and total IR luminosities. With data at longer wavelengths, we measure for the first time the emissivity index at these redshifts to provide more robust estimates of molecular gas masses based on dust continuum. The Band 8 observations of three out of four galaxies can only be reconciled with optically thin emission redward of rest-frame |$100\, {\rm \mu m}$|⁠. The derived dust peak temperatures at z ∼ 5.5 (⁠|$30\!-\!43\, {\rm K}$|⁠) are elevated compared to average local galaxies, however, |$\sim 10\, {\rm K}$| below what would be predicted from an extrapolation of the trend at z < 4. This behaviour can be explained by decreasing dust abundance (or density) towards high redshifts, which would cause the IR SED at the peak to be more optically thin, making hot dust more visible to the external observer. From the |$850{\hbox{-}}{\rm \mu m}$| dust continuum, we derive molecular gas masses between 1010 and |$10^{11}\, {\rm M_{\odot }}$| and gas fractions (gas over total mass) of |$30\!-\!80{{\ \rm per\ cent}}$| (gas depletion times of |$100\!-\!220\, {\rm Myr}$|⁠). All in all, our results provide a first measured benchmark SED to interpret future millimetre observations of normal, main-sequence galaxies in the early Universe. [ABSTRACT FROM AUTHOR]

The ALMA-ALPINE [CII] survey (A2C2S) aims at characterizing the properties of normal star-forming galaxies (SFGs) observed in the [CII]-158μm line in the period of rapid mass assembly at redshifts 4 < z < 6. Here we present the survey and the selection of 118 galaxies observed with ALMA, selected from large samples of galaxies with spectroscopic redshifts derived from UV-rest frame. The observed properties derived from the ALMA data are presented and discussed in terms of the overall detection rate in [CII] and far-IR continuum. The sample is representative of the SFG population at these redshifts. The overall detection rate is 61% down to a flux limit of 0.07 mJy. From a visual inspection of the [CII] data cubes together with the large wealth of ancillary data we find a surprisingly wide range of galaxy types, including 32.4% mergers, 25.7% extended and dispersion dominated, 13.5% rotating discs, and 16.2% compact, the remaining being too faint to be classified. ALPINE sets a reference sample for the gas distribution in normal star-forming galaxies at a key epoch in galaxy assembly, ideally suited for studies with future facilities like JWST and ELTs. [ABSTRACT FROM AUTHOR]

We perform a comprehensive analysis of the redshift evolution of the rest-UV spectra of star-forming galaxies out to z ∼ 5. We combine new z ∼ 5 measurements of H  i Ly α and low- and high-ionization interstellar metal absorption features with comparable measurements at z ∼ 2–4. We measure the equivalent widths of interstellar absorption features using stacked spectra in bins of Ly α equivalent width, performing corrections to Ly α strengths based on a model for the transmission of the intergalactic medium. We find a strong correlation between decreasing low-ionization absorption strength and increasing Ly α emission strength over the redshift range z ∼ 2–5, suggesting that both of these quantities are fundamentally linked to neutral gas covering fraction. At the highest Ly α equivalent widths, we observe evolution at z ∼ 5 towards greater Ly α emission strength at fixed low-ionization absorption strength. If we interpret the non-evolving relationship of Ly α emission strength and low-ionization line strength at z ∼ 2−4 as primarily reflecting the radiative transfer of Ly α photons, this evolution at z ∼ 5 suggests a higher intrinsic production rate of Ly α photons than at lower redshift. Our conclusion is supported by the joint evolution of the relationships among Ly α emission strength, interstellar absorption strength, and dust reddening. We perform additional analysis in bins of stellar mass, star formation rate, UV luminosity, and age, examining how the relationships between galaxy properties and Ly α emission evolve towards higher redshift. We conclude that increasing intrinsic Ly α photon production and strong detection of nebular C  iv emission (signalling lower metallicity) at z ∼ 5 indicate an elevated ionized photon production efficiency (ξion). [ABSTRACT FROM AUTHOR]

The advent of new sub-millimetre (sub-mm) observational facilities has stimulated the desire to model the sub-mm line emission of galaxies within cosmological galaxy formation models. This is typically done by applying sub-resolution recipes to describe the properties of the unresolved interstellar medium (ISM). While there is freedom in how one implements sub-resolution recipes, the impact of various choices has yet to be systematically explored. We combine a semi-analytic model of galaxy formation with chemical equilibrium networks and numerical radiative transfer models and explore how different choices for the sub-resolution modelling affect the predicted CO, [C  i ], and [C  ii ] emission of galaxies. A key component for a successful model includes a molecular cloud mass–size relation and scaling for the ultraviolet and cosmic ray radiation field that depend on local ISM properties. Our most successful model adopts a Plummer radial density profile for gas within molecular clouds. Different assumptions for the clumping of gas within molecular clouds and changes in the molecular cloud mass distribution function hardly affect the CO, [C  i ], and [C  ii ] luminosities of galaxies. At fixed star formation rate, the [C  ii ]–SFR ratio of galaxies scales inversely with the pressure acting on molecular clouds, increasing the molecular clouds density and hence decreasing the importance of [C  ii ] line cooling. We find that it is essential that a wide range of sub-mm emission lines arising in vastly different phases of the ISM are used as model constraints in order to limit the freedom in sub-grid choices. [ABSTRACT FROM AUTHOR]

Knowledge of the number density of Ha emitting galaxies is vital for assessing the scientific impact of the Euclid and Wide Field Infrared Survey Telescope (WFIRST) missions. In this work, we present predictions from a galaxy formation model, GALACTICUS, for the cumulative number counts of Ha-emitting galaxies. We couple GALACTICUS to three different dust attenuation methods and examine the counts using each method. A χ² minimisation approach is used to compare the model predictions to observed galaxy counts and calibrate the dust parameters. We find that weak dust attenuation is required for the GALACTICUS counts to be broadly consistent with the observations, though the optimum dust parameters return large values for χ², suggesting that further calibration of GALACTICUS is necessary. The model predictions are also consistent with observed estimates for the optical depth and the Ha luminosity function. Finally, we present forecasts for the redshift distributions and number counts for two Euclidlike and one WFIRST-like surveys. For a Euclid-like survey with redshift range of 0.9 ≤ z ≤ 1.8 and Ha + [N II] blended flux limit of 2 × 10-16 erg s-1 cm-2, we predict a number density between 3900 and 4800 galaxies per square degree. For a WFIRST-like survey with redshift range of 1 ≤ z ≤ 2 and blended flux limit of 1 × 10-16 erg s-1 cm-2, we predict a number density between 10 400 and 15 200 galaxies per square degree. [ABSTRACT FROM AUTHOR]