Due to their extremely dust-obscured nature, much uncertainty still exists surrounding the stellar mass growth and content in dusty, star-forming galaxies (DSFGs) at
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Abstract z > 1. In this work, we present a numerical model built using empirical data on DSFGs to estimate their stellar mass contributions across the first ∼10 Gyr of cosmic time. We generate a dust-obscured stellar mass function that extends beyond the mass limit of star-forming stellar mass functions in the literature, and predict that massive DSFGs constitute as much as 50%–100% of all star-forming galaxies withM ≥1011M ⊙atz > 1. We predict the number density of massive DSFGs and find general agreement with observations, although more data is needed to narrow wide observational uncertainties. We forward-model mock massive DSFGs to their quiescent descendants and find remarkable agreement with observations from the literature demonstrating that, to first order, massive DSFGs are a sufficient ancestral population to describe the prevalence of massive quiescent galaxies atz > 1. We predict that massive DSFGs and their descendants contribute as much as 25%–60% to the cosmic stellar mass density during the peak of cosmic star formation, and predict an intense epoch of population growth during the ∼1 Gyr fromz = 6 to 3 during which the majority of the most massive galaxies at high-z grow and then quench. Future studies seeking to understand massive galaxy growth and evolution in the early universe should strategize synergies with data from the latest observatories (e.g., JWST and the Atacama Large Millimeter/submillimeter Array) to better include the heavily dust-obscured galaxy population. -
Abstract We present a sample of 30 massive (log( M * / M ⊙ ) > 11) z = 3–5 quiescent galaxies selected from the Spitzer-HETDEX Exploratory Large Area (SHELA) Survey and observed at 1.1 mm with Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 observations. These ALMA observations would detect even modest levels of dust-obscured star formation, on the order of ∼20 M ⊙ yr −1 at z ∼ 4 at the 1 σ level, allowing us to quantify the amount of contamination from dusty star-forming sources in our quiescent sample. Starting with a parent sample of candidate massive quiescent galaxies from the Stevans et al. v1 SHELA catalog, we use the Bayesian B agpipes spectral energy distribution fitting code to derive robust stellar masses ( M * ) and star formation rates (SFRs) for these sources, and select a conservative sample of 36 candidate massive ( M * > 10 11 M ⊙ ) quiescent galaxies, with specific SFRs >2 σ below the Salmon et al. star-forming main sequence at z ∼ 4. Based on the ALMA imaging, six of these candidate quiescent galaxies show the presence of significant dust-obscured star formation, and thus were removed from our final sample. This implies a ∼17% contamination rate from dusty star-forming galaxies with our selection criteria using the v1 SHELA catalog. This conservatively selected quiescent galaxy sample at z = 3–5 will provide excellent targets for future observations to constrain better how massive galaxies can both grow and shut down their star formation in a relatively short period.more » « less
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ABSTRACT We present a spectroscopic survey of Ly α emitters in the Extended Groth Strip (EGS) field, targeting the regime near the Epoch of Reionization. Using Keck/DEep Imaging Multi-Object Spectrograph, we observed 947 high-z candidates with photometric redshifts from 3 < zphot < 7 and down to an H-band (Hubble Space Telescope/Wide Field Camera 3 F160W) magnitude limit of <27.5. Observations were taken over the course of eight nights, with integration times ranging from 4 to 7.8 h. Our survey secured 137 unique redshifts, 126 of which are Ly α emitters at 2.8 < z < 6.3 with a mean redshift of $\overline{z} = 4.3$. We provide a comprehensive redshift catalogue for our targets, as well as the reduced one- and two-dimensional spectra for each object. These observations will provide an important auxiliary data set for the JWST Directors Discretionary Early Release Science programme the Cosmic Evolution Early Release Science Survey, which recently completed near- and mid-infrared imaging and spectroscopy of galaxies in the EGS field.
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Abstract We report the discovery of 15 exceptionally luminous 10 ≲
z ≲ 14 candidate galaxies discovered in the first 0.28 deg2of JWST/NIRCam imaging from the COSMOS-Web survey. These sources span rest-frame UV magnitudes of −20.5 >M UV> −22, and thus constitute the most intrinsically luminousz ≳ 10 candidates identified by JWST to date. Selected via NIRCam imaging, deep ground-based observations corroborate their detection and help significantly constrain their photometric redshifts. We analyze their spectral energy distributions using multiple open-source codes and evaluate the probability of low-redshift solutions; we conclude that 12/15 (80%) are likely genuinez ≳ 10 sources and 3/15 (20%) likely low-redshift contaminants. Three of ourz ∼ 12 candidates push the limits of early stellar mass assembly: they have estimated stellar masses ∼ 5 × 109M ⊙, implying an effective stellar baryon fraction ofϵ ⋆∼ 0.2−0.5, whereϵ ⋆≡M ⋆/(f b M halo). The assembly of such stellar reservoirs is made possible due to rapid, burst-driven star formation on timescales < 100 Myr where the star formation rate may far outpace the growth of the underlying dark matter halos. This is supported by the similar volume densities inferred forM ⋆∼ 1010M ⊙galaxies relative toM ⋆∼ 109M ⊙—both about 10−6Mpc−3—implying they live in halos of comparable mass. At such high redshifts, the duty cycle for starbursts would be of order unity, which could cause the observed change in the shape of the UV luminosity function from a double power law to a Schechter function atz ≈ 8. Spectroscopic redshift confirmation and ensuing constraints of their masses will be critical to understand how, and if, such early massive galaxies push the limits of galaxy formation in the Lambda cold dark matter paradigm.Free, publicly-accessible full text available April 1, 2025 -
Seagroves, Scott ; Barnes, Austin ; Metevier, Anne ; Porter, Jason ; Hunter, Lisa (Ed.)Much of the ISEE Professional Development Program (PDP)’s long-term value arises from participants transferring teaching approaches they develop in the course of designing and facilitating a PDP inquiry activity to other contexts throughout their careers. PDP participants encounter frameworks such as the inquiry framework and the equity and inclusion focus areas, and are encouraged explicitly to become informed consumers of further scholarship on teaching and learning. Many participants resonate especially with the PDP’s emphasis on equity and inclusion in STEM teaching, and meld lessons from the PDP with their lived experiences as well as other scholarship on equity-minded or culturally responsive educational practices. Our panel shares four perspectives on extending lessons from the PDP to new contexts: mentoring students and developing interactive lessons in molecular biology, designing astronomy activities from a culturally relevant and culturally responsive standpoint, incorporating inquiry activities into a large astronomy lecture course, and helping academic programs across a university adopt equity-minded practices for assessing learning outcomes.more » « less
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Abstract A complete census of dusty star-forming galaxies (DSFGs) at early epochs is necessary to constrain the obscured contribution to the cosmic star formation rate density (CSFRD); however, DSFGs beyond
z ∼ 4 are both rare and hard to identify from photometric data alone due to degeneracies in submillimeter photometry with redshift. Here, we present a pilot study obtaining follow-up Atacama Large Millimeter Array (ALMA) 2 mm observations of a complete sample of 39 850μ m-bright dusty galaxies in the SSA22 field. Empirical modeling suggests 2 mm imaging of existing samples of DSFGs selected at 850μ m—1 mm can quickly and easily isolate the “needle in a haystack” DSFGs that sit atz > 4 or beyond. Combining archival submillimeter imaging with our measured ALMA 2 mm photometry (1σ ∼ 0.08 mJy beam−1rms), we characterize the galaxies’ IR spectral energy distributions (SEDs) and use them to constrain redshifts. With available redshift constraints fit via the combination of six submillimeter bands, we identify 6/39 high-z candidates each with >50% likelihood to sit atz > 4, and find a positive correlation between redshift and 2 mm flux density. Specifically, our models suggest the addition of 2 mm to a moderately constrained IR SED will improve the accuracy of a millimeter-derived redshift from Δz /(1 +z ) = 0.3 to Δz /(1 +z ) = 0.2. Our IR SED characterizations provide evidence for relatively high-emissivity spectral indices (〈β 〉 = 2.4 ± 0.3) in the sample. We measure that especially bright (S 850μ m > 5.55 mJy) DSFGs contribute ∼10% to the cosmic-averaged CSFRD from 2 <z < 5, confirming findings from previous work with similar samples. -
Abstract We present the Texas Euclid Survey for Ly
α (TESLA), a spectroscopic survey in the 10 deg2of the Euclid North Ecliptic Pole (NEP) field. Using TESLA, we study how the physical properties of Lyα emitters (LAEs) correlate with Lyα emission to understand the escape of Lyα emission from galaxies at redshifts of 2–3.5. We present an analysis of 43 LAEs performed in the NEP field using early data from the TESLA survey. We use Subaru Hyper Suprime-Cam imaging in thegrizy bands, Spitzer/IRAC channels 1 and 2 from the Hawaii 20 deg2(H20) survey, and spectra acquired by the Visible Integral-Field Replicable Unit Spectrograph (VIRUS) on the Hobby–Eberly Telescope. We perform spectral energy distribution (SED) fitting to compute the galaxy properties of 43 LAEs, and study correlations between stellar mass, star formation rate (SFR), and dust to the Lyα rest-frame equivalent width (W Lyα ). We uncover marginal (1σ significance) correlations between stellar mass andW Lyα , and SFR andW Lyα , with a Spearman correlation coefficient of −0. and −0. , respectively. We show that theW Lyα distribution of the 43 LAEs is consistent with being drawn from an exponential distribution with an e-folding scale ofW 0= 150 Å. Once complete the TESLA survey will enable the study of ≳50,000 LAEs to explore more correlations between galaxy properties andW Lyα . The large sample size will allow the construction of a predictive model forW Lyα as a function of SED-derived galaxy properties, which could be used to improve Lyα -based constraints on reionization. -
Abstract We present Ly α and ultraviolet (UV)-continuum luminosity functions (LFs) of galaxies and active galactic nuclei (AGNs) at z = 2.0–3.5 determined by the untargeted optical spectroscopic survey of the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX). We combine deep Subaru imaging with HETDEX spectra resulting in 11.4 deg 2 of fiber spectra sky coverage, obtaining 18,320 galaxies spectroscopically identified with Ly α emission, 2126 of which host type 1 AGNs showing broad (FWHM > 1000 km s −1 ) Ly α emission lines. We derive the Ly α (UV) LF over 2 orders of magnitude covering bright galaxies and AGNs in log L Ly α / [ erg s − 1 ] = 43.3 – 45.5 (−27 < M UV < −20) by the 1/ V max estimator. Our results reveal that the bright-end hump of the Ly α LF is composed of type 1 AGNs. In conjunction with previous spectroscopic results at the faint end, we measure a slope of the best-fit Schechter function to be α Sch = − 1.70 − 0.14 + 0.13 , which indicates that α Sch steepens from z = 2–3 toward high redshift. Our UV LF agrees well with previous AGN UV LFs and extends to faint-AGN and bright-galaxy regimes. The number fraction of Ly α -emitting objects ( X LAE ) increases from M UV * ∼ − 21 to bright magnitude due to the contribution of type 1 AGNs, while previous studies claim that X Ly α decreases from faint magnitudes to M UV * , suggesting a valley in the X Ly α –magnitude relation at M UV * . Comparing our UV LF of type 1 AGNs at z = 2–3 with those at z = 0, we find that the number density of faint ( M UV > −21) type 1 AGNs increases from z ∼ 2 to 0, as opposed to the evolution of bright ( M UV < −21) type 1 AGNs, suggesting AGN downsizing in the rest-frame UV luminosity.more » « less
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Abstract The 2 mm Mapping Obscuration to Reionization with ALMA (MORA) Survey was designed to detect high-redshift ( z ≳ 4), massive, dusty star-forming galaxies (DSFGs). Here we present two likely high-redshift sources, identified in the survey, whose physical characteristics are consistent with a class of optical/near-infrared (OIR)-invisible DSFGs found elsewhere in the literature. We first perform a rigorous analysis of all available photometric data to fit spectral energy distributions and estimate redshifts before deriving physical properties based on our findings. Our results suggest the two galaxies, called MORA-5 and MORA-9, represent two extremes of the “OIR-dark” class of DSFGs. MORA-5 ( z phot = 4.3 − 1.3 + 1.5 ) is a significantly more active starburst with a star formation rate (SFR) of 830 − 190 + 340 M ⊙ yr −1 compared to MORA-9 ( z phot = 4.3 − 1.0 + 1.3 ), whose SFR is a modest 200 − 60 + 250 M ⊙ yr −1 . Based on the stellar masses ( M ⋆ ≈ 10 10−11 M ⊙ ), space density ( n ∼ (5 ± 2) × 10 −6 Mpc −3 , which incorporates two other spectroscopically confirmed OIR-dark DSFGs in the MORA sample at z = 4.6 and z = 5.9), and gas depletion timescales (<1 Gyr) of these sources, we find evidence supporting the theory that OIR-dark DSFGs are the progenitors of recently discovered 3 < z < 4 massive quiescent galaxies.more » « less