Reed College

Abstract Recent observations from the James Webb Space Telescope have revealed unexpectedly luminous galaxies, exhibiting stellar masses and luminosities significantly higher than predicted by theoretical models at Cosmic Dawn. In this study, we present a suite of cosmological zoomed-in simulations targeting high-redshift ( z ≥ 10) galaxies with dark matter halo masses in the range 10 10 –10 11 M ⊙ at z = 10, using state-of-the-art galaxy formation simulation codes ( Enzo , Ramses , Changa , Gadget-3 , Gadget-4 , and Gizmo ). This study aims to evaluate the convergence of the participating codes and their reproducibility of high-redshift galaxies with the galaxy formation model calibrated at relatively low redshift, without additional physics for high-redshift environments. The subgrid physics follows the AGORA CosmoRun framework, with adjustments to resolution and initial conditions to emulate similar physical environments in the early Universe. The participating codes show consistent results for key galaxy properties (e.g., stellar mass), but also reveal notable differences (e.g., metallicity), indicating that galaxy properties at high redshifts are highly sensitive to the feedback implementation of the simulation. Massive halos ( M halo ≥5 × 10 10 M ⊙ at z = 10) succeed in reproducing observed stellar masses, metallicities, and UV luminosities at 10 ≤ z ≤ 12 without requiring additional subgrid physics, but tend to underpredict those properties at higher redshift. We also find that varying the dust-to-metal ratio modestly affects UV luminosity of simulated galaxies, whereas the absence of dust significantly enhances it. In future work, higher-resolution simulations will be conducted to better understand the formation and evolution of galaxies at Cosmic Dawn.

We arranged conditions of social enrichment for a group of six pigeons as part of a larger program of research concerned with an animal model of gambling. When not in their experimental sessions, the pigeons lived together in a free-flying aviary, interacting with each other and with a physical environment that included perches, nesting materials, and nesting boxes. This enabled a range of species-typical social behavior including courtship, mating, and reproductive behavior. To minimize human involvement and the potential stress of daily captures, we devised procedures whereby the pigeons could choose to exit each day by flying one-by-one on cue into a box attached to the porthole door of the aviary from which they were transported to the test apparatus for their daily experimental sessions. By the end of this training, all pigeons were consistently entering the box independently in the presence of their own distinctive cues for transport to the session, and this continued for a maintenance phase during which each pigeon chose to participate in 120 daily sessions. The findings show the power of using reinforcement-based methods to solve practical problems in animal enrichment and welfare, balancing the welfare needs of the animals with the needs of the research.

Abstract Human language enables the exchange of complex information and precise instructions for collaborative planning and action. It rapidly evolves through social learning, generating diverse cultural communication signals used not only with other humans, but also with domesticated animals bred or trained to respond. More rarely, humans communicate with untrained, wild animals to coordinate joint actions, yet little is known about how or why these human‐to‐wildlife signals diversify. Human‐wildlife cooperation allows us to investigate whether human signals directed at untrained, wild animals exhibit regional variation, akin to dialects in human language. We investigated regional variation in human signals used to cooperate with greater honeyguides ( Indicator indicator ): wild birds that guide people to bees' nests in exchange for access to beeswax. Across 13 villages in northern Mozambique, we tested whether human honey‐hunting calls varied with spatial distance, as expected if regional dialects had emerged, or with measures of the physical environment affecting sound propagation, as expected if calls were shaped by habitat acoustics. Our analyses showed that trills, grunts, whoops, and whistles used while cooperating with honeyguides (i) consistently varied with spatial distance between villages, (ii) varied irrespective of the local habitat, and (iii) appeared to be adopted by immigrant honey‐hunters to match local calls. These findings suggest that regional variation in human‐to‐wildlife signals is shaped primarily by human social factors, forming a landscape of interspecific signal diversity similar to human language dialects. Honeyguides cooperate effectively with honey‐hunters throughout this landscape, suggesting that they accommodate (and likely reinforce) cultural differences by learning the local interspecies dialect. Read the free Plain Language Summary for this article on the Journal blog.

The purpose of this note is to introduce the CUBE, a virtual reality immersion that was developed to help visualize electromagnetic fields, particularly the less familiar radiation fields students typically encounter in upper level physics courses. We discuss the pedagogical motivation for different features found in the software, and provide a brief overview of its use.

Abstract We investigate how differences in the stellar feedback produce disks with different morphologies in Milky Way–like progenitors over 1 ≤ z ≤ 5, using eight state-of-the-art cosmological hydrodynamics simulation codes in the AGORA project. In three of the participating codes, a distinct, rotation-dominated inner core emerges with a formation timescale of ≲300 Myr, largely driven by a major merger event, while two other codes exhibit similar signs of wet compaction—gaseous shrinkage into a compact starburst phase—at earlier epochs. The remaining three codes show only weak evidence of wet compaction. Consequently, we divide the simulated galaxies into two groups: those with strong compaction signatures and those with weaker ones. Galaxies in these two groups differ in size, stellar age gradients, and disk-to-total mass ratios. Specifically, codes with strong wet compaction build their outer disks in an inside-out fashion, leading to negative age gradients, whereas codes with weaker compaction feature flat or positive age gradients caused primarily by outward stellar migration. Although the stellar half-mass radii of these two groups diverge at z ∼ 3, the inclusion of dust extinction brings their sizes and shapes in mock observations closer to each other and to observed galaxies. We attribute the observed morphological differences primarily to variations in the stellar feedback implementations—such as delayed cooling timescales, and feedback strengths—that regulate both the onset and duration of compaction. Overall, our results suggest that disk assembly at high redshifts is highly sensitive to the details of the stellar feedback prescriptions in simulations.

Abstract. An improved mechanistic model of mercury redox chemistry has recently been implemented in the GEOS-Chem model. In this study, GEOS-Chem simulations were compared to ambient measurements made during a high-oxidized mercury episode that originated in the free troposphere at a mountaintop site in Colorado, USA (40.455° N, −106.744° W, 3220 m above sea level). Measurements were collected with a dual channel atmospheric oxidized mercury measurement system that has been shown to accurately quantify oxidized mercury compounds in ambient air. The model and observations showed similar temporal trends for elemental and oxidized mercury (R2 of 0.54 to 0.79) and similar elemental mercury concentrations (normalized mean square error of 0.04 in the base model). However, the base model only produced 17 % of the maximum oxidized mercury observed in the dual channel system. In sensitivity tests with increased oxidation rates, the model still only produced, at most, 23 % of maximum observed oxidized mercury. In addition to underestimating net mercury oxidation, an analysis of elemental to oxidized mercury slopes indicated the model overestimated oxidized mercury deposition. An analysis of GEOS-Chem results from a separate study confirmed that while GEOS-Chem is able to simulate the range of measured oxidized mercury in low-oxidized mercury episodes and locations it consistently underestimates measured values during high-oxidized mercury periods at surface locations in western USA.