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Abstract Galaxies that are invisible in deep optical–near-infrared imaging but detected at longer wavelengths have been the focus of several recent observational studies, with speculation that they could constitute a substantial missing population and even dominate the cosmic star formation rate density atz≳ 4. The depths now achievable with JWST at the longest wavelengths probed by the Hubble Space Telescope (HST), coupled with the transformative resolution at longer wavelengths, are already enabling detailed, spatially resolved characterization of sources that were invisible to HST, often known as “HST-dark” galaxies. However, until now, there has been little theoretical work to compare against. We present the first simulation-based study of this population, using highly resolved galaxies from the Feedback in Realistic Environments project, with multiwavelength images along several lines of sight forward-modeled using radiative transfer. We naturally recover a population of modeled sources that meet commonly used selection criteria (H_AB> 27 mag andH_AB− F444W > 2.3). These simulated HST-dark galaxies lie at high redshifts (z= 4–7), have high levels of dust attenuation (A_V= 2–4), and display compact recent star formation (R_1/2,4.4μm≲ 1 kpc). Orientation is very important: for all but one of the 17 simulated galaxy snapshots with HST-dark sight lines, there exist other sight lines that do not meet the criteria. This result has important implications for comparisons between observations and models that do not resolve the detailed star-dust geometry, such as semianalytic models or coarsely resolved hydrodynamical simulations. Critically, we demonstrate that HST-dark sources are not an unexpected or exotic population, but a subset of high-redshift, highly dust-attenuated sources viewed along certain lines of sight. 

ABSTRACT Recent works have suggested that energy balance spectral energy distribution (SED) fitting codes may be of limited use for studying high-redshift galaxies for which the observed ultraviolet and far-infrared emission are offset (spatially ‘decoupled’). It has been proposed that such offsets could lead energy balance codes to miscalculate the overall energetics, preventing them from recovering such galaxies’ true properties. In this work, we test how well the SED fitting code magphys can recover the stellar mass, star formation rate (SFR), specific SFR, dust mass, and luminosity by fitting 6706 synthetic SEDs generated from four zoom-in simulations of dusty, high-redshift galaxies from the FIRE project via dust continuum radiative transfer. Comparing our panchromatic results (using wavelengths 0.4–500 μm, and spanning 1 < z < 8) with fits based on either the starlight ($$\lambda _\mathrm{eff} \le 2.2\, \mu$$m) or dust ($$\ge 100\, \mu$$m) alone, we highlight the power of considering the full range of multiwavelength data alongside an energy balance criterion. Overall, we obtain acceptable fits for 83 per cent of the synthetic SEDs, though the success rate falls rapidly beyond z ≈ 4, in part due to the sparser sampling of the priors at earlier times since SFHs must be physically plausible (i.e. shorter than the age of the universe). We use the ground truth from the simulations to show that when the quality of fit is acceptable, the fidelity of magphys estimates is independent of the degree of UV/FIR offset, with performance very similar to that previously reported for local galaxies. 

Teaching observations can be used in multiple ways to describe and assess instruction. We addressed the challenge of measuring instructional change with observational protocols, data that often do not lend themselves easily to statistical comparisons. We first grouped 790 mathematics classes using Latent Profile Analysis and found four reliable categories of classes. Based on the grouping we proposed a proportional measure called Proportion Non-Didactic Lecture (PND). The measure is the proportion of interactive to lecture classes for each instructor. The PND worked in simple hypothesis tests but lacked some statistical power due to possible scaler ceiling effects. The measure correlated highly with a dependent measure derived from the Reformed Teaching Observation Protocol (RTOP), a holistic observational measure. The PND also provided effective descriptions and visualizations of instructional approaches and how these changed from pre to post. 

Abstract Single flux density measurements at observed-frame submillimeter and millimeter wavelengths are commonly used to probe dust and gas masses in galaxies. In this Letter, we explore the robustness of this method to infer dust mass, focusing on quiescent galaxies, using a series of controlled experiments on four massive halos from the Feedback in Realistic Environments project. Our starting point is four star-forming central galaxies at seven redshifts betweenz= 1.5 andz= 4.5. We generate modified quiescent galaxies that have been quenched for 100 Myr, 500 Myr, or 1 Gyr prior to each of the studied redshifts by reassigning stellar ages. We derive spectral energy distributions for each fiducial and modified galaxy using radiative transfer. We demonstrate that the dust mass inferred is highly dependent on the assumed dust temperature,T_dust, which is often unconstrained observationally. Motivated by recent work on quiescent galaxies that assumedT_dust∼ 25 K, we show that the ratio between dust mass and 1.3 mm flux density can be higher than inferred by up to an order of magnitude, due to the considerably lower dust temperatures seen in non-star-forming galaxies. This can lead to an underestimation of dust mass (and, when submillimeter flux density is used as a proxy for molecular gas content and gas mass). This underestimation is most severe at higher redshifts, where the observed-frame 1.3 mm flux density probes rest-frame wavelengths far from the Rayleigh–Jeans regime, and hence depends superlinearly on dust temperature. We fit relations between ratios of rest-frame far-infrared flux densities and mass-weighted dust temperature that can be used to constrain dust temperatures from observations and hence derive more reliable dust and molecular gas masses. 

ABSTRACT Recent years have seen growing interest in post-processing cosmological simulations with radiative transfer codes to predict observable fluxes for simulated galaxies. However, this can be slow, and requires a number of assumptions in cases where simulations do not resolve the interstellar medium (ISM). Zoom-in simulations better resolve the detailed structure of the ISM and the geometry of stars and gas; however, statistics are limited due to the computational cost of simulating even a single halo. In this paper, we make use of a set of high-resolution, cosmological zoom-in simulations of massive ($$M_{\star }\gtrsim 10^{10.5}\, \rm {M_{\odot }}$$ at z = 2), star-forming galaxies from the FIRE suite. We run the skirt radiative transfer code on hundreds of snapshots in the redshift range 1.5 < z < 5 and calibrate a power-law scaling relation between dust mass, star formation rate, and $$870\, \mu \rm {m}$$ flux density. The derived scaling relation shows encouraging consistency with observational results from the sub-millimetre-selected AS2UDS sample. We extend this to other wavelengths, deriving scaling relations between dust mass, stellar mass, star formation rate, and redshift and sub-millimetre flux density at observed-frame wavelengths between $$\sim \! 340$$ and $$\sim \! 870\, \mu \rm {m}$$. We then apply the scaling relations to galaxies drawn from EAGLE, a large box cosmological simulation. We show that the scaling relations predict EAGLE sub-millimetre number counts that agree well with previous results that were derived using far more computationally expensive radiative transfer techniques. Our scaling relations can be applied to other simulations and semi-analytical or semi-empirical models to generate robust and fast predictions for sub-millimetre number counts. 

Gendered differences in academic confidence and self-efficacy between men and women are well-documented. In STEM fields and specifically in engineering, such differences have important consequences in that students low on these constructs are often more prone to leave their degree programs. While this evidence base is fairly established, less is known about the extent to which men and women show differences in confidence of team success, or collective efficacy, which may also be consequential in decisions to join and persist in design team experiences, or even to stay in or leave an engineering major, especially for first-year students. In this analysis, we quantitatively investigated gendered differences in confidence of team success and collective efficacy among first-year engineering students working on semester-long design projects in stable teams. Using a software tool built to support equitable teamwork, survey data on team confidence and collective efficacy was collected for these engineering students as well as for students in other courses for the sake of comparison. Three hierarchical linear models were fit to the data from 1,806 students across 31 unique course/term combinations. The results were mixed. In two of these analyses, we identified significant interactions between gender and team confidence. Specifically, men generally reported higher team confidence scores than women throughout the term with women eventually catching up, and team confidence ratings increased for men but not women following a lesson on imposter syndrome. No gendered differences were observed with respect to a collective efficacy scale administered near the middle and end of the term, however. In all cases, the results were consistent across course type (engineering, business, and others). 

This work-in-progress paper reports on the assessment of an intervention on team communication and decision making processes to see whether such an intervention is related to improvement in the rating of equity of idea contributions. A hierarchical linear model was fit to teamwork data from 3,721 students in 40 courses. We find that students’ reports of equitable idea sharing are actually lower after the intervention than before; we hypothesize that the decreased rating might reflect increased student awareness of inequities rather than a true decrease in equitable idea sharing. This pattern held for most gender and racial groups, with the notable exception of non-binary students, who instead reported greater idea equity post-intervention, though we note the small sample size for this group. Finally, we find that decreases in reported idea sharing were largest when students reported the intervention was “highly relevant” to their team yet “not very helpful”. 

Abstract We present the average rest-frame spectrum of the final catalog of dusty star-forming galaxies (DSFGs) selected from the South Pole Telescope's SPT-SZ survey and measured with Band 3 of the Atacama Large Millimeter/submillimeter Array. This work builds on the previous average rest-frame spectrum, given in Spilker et al. (2014) for the first 22 sources, and is comprised of a total of 78 sources, normalized by their respective apparent dust masses. The spectrum spans 1.9 <z< 6.9 and covers rest-frame frequencies of 240–800 GHz. Combining this data with low-JCO observations from the Australia Telescope Compact Array, we detect multiple bright line features from¹²CO, [Ci], and H₂O, as well as fainter molecular transitions from¹³CO, HCN, HCO⁺, HNC, CN, H₂O⁺, and CH. We use these detections, along with limits from other molecules, to characterize the typical properties of the interstellar medium (ISM) for these high-redshift DSFGs. We are able to divide the large sample into subsets in order to explore how the average spectrum changes with various galaxy properties, such as effective dust temperature. We find that systems with hotter dust temperatures exhibit differences in the bright¹²CO emission lines, and contain either warmer and more excited dense gas tracers or larger dense gas reservoirs. These observations will serve as a reference point to studies of the ISM in distant luminous DSFGs (L_IR> 10¹²L_⊙), and will inform studies of chemical evolution before the peak epoch of star formation atz= 2–3. 

High-redshift dusty star-forming galaxies with very high star formation rates (500−3000 M ⊙ yr −1 ) are key to understanding the formation of the most extreme galaxies in the early Universe. Characterising the gas reservoir of these systems can reveal the driving factor behind the high star formation. Using molecular gas tracers such as, high- J CO lines, neutral carbon lines, and the dust continuum, we can estimate the gas density and radiation field intensity in their interstellar media. In this paper, we present high resolution (∼0.4″) observations of CO(7−6), [CI](2−1), and dust continuum of three lensed galaxies from the South pole telescope – sub-millimetre galaxies (SPT-SMG) sample at z  ∼ 3 with the Atacama Large Millimetre/submillimetre Array. Our sources have high intrinsic star formation rates (> 850 M ⊙ yr −1 ) and rather short depletion timescales (< 100 Myr). Based on the L [CI](2−1) / L CO(7 − 6) and L [CI](2−1) / L IR ratios, our galaxy sample has similar radiation field intensities and gas densities compared to other submillimetre galaxies. We performed visibility-based lens modelling on these objects to reconstruct the kinematics in the source plane. We find that the cold gas masses of the sources are compatible with simple dynamical mass estimates using ULIRG-like values of the CO-H 2 conversion factor α CO , but not Milky Way-like values. We find diverse source kinematics in our sample: SPT0103−45 and SPT2147−50 are likely rotating disks, while SPT2357−51 is possibly a major merger. The analysis presented in the paper could be extended to a larger sample to determine better statistics of morphologies and interstellar medium properties of high- z dusty star-forming galaxies. 

ABSTRACT The galaxy size–stellar mass and central surface density–stellar mass relationships are fundamental observational constraints on galaxy formation models. However, inferring the physical size of a galaxy from observed stellar emission is non-trivial due to various observational effects, such as the mass-to-light ratio variations that can be caused by non-uniform stellar ages, metallicities, and dust attenuation. Consequently, forward-modelling light-based sizes from simulations is desirable. In this work, we use the skirt  dust radiative transfer code to generate synthetic observations of massive galaxies ($$M_{*}\sim 10^{11}\, \rm {M_{\odot }}$$ at z = 2, hosted by haloes of mass $$M_{\rm {halo}}\sim 10^{12.5}\, \rm {M_{\odot }}$$) from high-resolution cosmological zoom-in simulations that form part of the Feedback In Realistic Environments project. The simulations used in this paper include explicit stellar feedback but no active galactic nucleus (AGN) feedback. From each mock observation, we infer the effective radius (Re), as well as the stellar mass surface density within this radius and within $$1\, \rm {kpc}$$ (Σe and Σ1, respectively). We first investigate how well the intrinsic half-mass radius and stellar mass surface density can be inferred from observables. The majority of predicted sizes and surface densities are within a factor of 2 of the intrinsic values. We then compare our predictions to the observed size–mass relationship and the Σ1−M⋆ and Σe−M⋆ relationships. At z ≳ 2, the simulated massive galaxies are in general agreement with observational scaling relations. At z ≲ 2, they evolve to become too compact but still star forming, in the stellar mass and redshift regime where many of them should be quenched. Our results suggest that some additional source of feedback, such as AGN-driven outflows, is necessary in order to decrease the central densities of the simulated massive galaxies to bring them into agreement with observations at z ≲ 2.