Surface Brightness Evolution of Galaxies in the CANDELS GOODS Fields up to z∼6z \sim 6: High-z Galaxies are Unique or Remain Undetected

We investigate the rest-frame Ultraviolet (UV, $\lambda\sim2000$\AA) surface brightness (SB) evolution of galaxies up to $z\sim6$ using a variety of deep Hubble Space Telescope imaging. UV SB is a measure of the density of emission from mostly young stars and correlates with an unknown combination of star formation rate, initial mass function, cold gas mass density, dust attenuation, and the size evolution of galaxies. In addition to physical effects, the SB is, unlike magnitude, a more direct way in which a galaxy's detectability is determined. We find a very strong evolution in the intrinsic SB distribution which declines as $(1+z)^{3}$, decreasing by 4-5 mag arcsec$^{-2}$ between $z=6$ to $z=1$. This change is much larger than expected in terms of the evolution in UV luminosity, sizes or dust extinction and we demonstrate that this evolution is 'unnatural' and due to selection biases. We also find no strong correlation between mass and UV SB. Thus, deep HST imaging is unable to discover all of the most massive galaxies in the distant universe. Through simulations we show that only $\sim15$\% of galaxies that we can detect at $z=2$ would be detected at high-$z$. We furthermore explore possible origins of high SB galaxies at high-$z$ by investigating the relationship between intrinsic SB and star formation rates. We conclude that ultra-high SB galaxies are produced by very gas rich dense galaxies which are in a unique phase of evolution, possibly produced by mergers. Analogues of such galaxies do not exist in the relatively nearby universe.Comment: Accepted for publication in AAS Journals (ApJ). 25 pages, 14 figure

COVID and Coraje: Negotiating Latinx Immigrant Experiences of the Pandemic

11 pagesIn this paper, we compare observations from engaged ethnography and participant observation with Latinx immigrants in Colorado and Oregon during the COVID-19 pandemic. In particular, we focus on lived experiences of structural vulnerability, as well as the ways in which COVID-related disparities have become internalized as stigma and have amplified immigrants’ experiences of stress, anxiety, and “aislamiento,” or isolation. Indeed, Latinx immigrants in the US—especially those without legal status and those in mixed-status families—face a range of exclusions, discourses of blame and (un)deservingness, and forms of precarity that have contributed to disproportionate risk, suffering, and fear as the pandemic has unfolded. At the same time, by laying bare blatant injustices and racist exclusions, the pandemic has prompted some Latinx immigrants in our research and advocacy sites to enact new forms of resistance and contestation. We detail the range of ways which, in efforts to stay healthy and to challenge discriminatory portrayals of themselves as either disease carriers unlikely to heed public health warnings or as “public charges,” they insist upon their own rights, worth, belonging, and dignity. Finally, we conclude by discussing some of the ways in which these two U.S. states—and the health and social service organizations working with Latinx communities within them—have attempted to address coronavirus disparities among Latinx communities, showing how particular approaches can assuage short-term suffering and improve access to healthcare and other social supports, while others may create a new set of barriers to access for already marginalized communitiesNational Science Foundatio

Immigrant Communities and the Public Charge Rule

8 pages

Galaxy Merger Rates up to z ~ 3 using a Bayesian Deep Learning Model: A Major-Merger classifier using IllustrisTNG Simulation data

Merging is potentially the dominate process in galaxy formation, yet there is still debate about its history over cosmic time. To address this we classify major mergers and measure galaxy merger rates up to z $\sim$ 3 in all five CANDELS fields (UDS, EGS, GOODS-S, GOODS-N, COSMOS) using deep learning convolutional neural networks (CNNs) trained with simulated galaxies from the IllustrisTNG cosmological simulation. The deep learning architecture used is objectively selected by a Bayesian Optmization process over the range of possible hyperparameters. We show that our model can achieve 90% accuracy when classifying mergers from the simulation, and has the additional feature of separating mergers before the infall of stellar masses from post mergers. We compare our machine learning classifications on CANDELS galaxies and compare with visual merger classifications from Kartaltepe et al. (2015), and show that they are broadly consistent. We finish by demonstrating that our model is capable of measuring galaxy merger rates, $\mathcal{R}$, that are consistent with results found for CANDELS galaxies using close pairs statistics, with $\mathcal{R}(z) = 0.02 \pm 0.004 \times (1 +z) ^ {2.76 \pm 0.21}$. This is the first general agreement between major mergers measured using pairs and structure at z < 3.Comment: 22 pages, 13 figures, 3 tables, accepted for publication in Ap

Galaxy evolution in all five CANDELS fields and IllustrisTNG: morphological, structural, and the major merger evolution to z 3

Large scale structure and cosmolog

Protecting Undocumented Students Post-Election

5 pages; news article from a websit

Brief behavioural activation for adolescent depression: working with complexity and risk

Given the long-term negative outcomes associated with depression in adolescence, there is a pressing need to develop brief, evidence based treatments that are accessible to more young people experiencing low mood. Behavioural Activation (BA) is an effective treatment for adult depression, however little research has focused on the use of BA with depressed adolescents, particularly with briefer forms of BA. In this article we outline an adaptation of brief Behavioral Activation Treatment of Depression (BATD) designed for adolescents and delivered in eight sessions (Brief BA). This case example illustrates how a structured, brief intervention was useful for a depressed young person with a number of complicating and risk factors

Pre-Columbian fire management and control of climate-driven floodwaters over 3,500 years in southwestern Amazonia

In landscapes that support economic and cultural activities, human communities actively manage environments and environmental change at a variety of spatial scales that complicate the effects of continental-scale climate. Here, we demonstrate how hydrological conditions were modified by humans against the backdrop of Holocene climate change in southwestern Amazonia. Paleoecological investigations (phytoliths, charcoal, pollen, diatoms) of two sediment cores extracted from within the same permanent wetland, ∼22 km apart, show a 1,500-y difference in when the intensification of land use and management occurred, including raised field agriculture, fire regime, and agroforestry. Although rising precipitation is well known during the mid to late Holocene, human actions manipulated climate-driven hydrological changes on the landscape, revealing differing histories of human landscape domestication. Environmental factors are unable to account for local differences without the mediation of human communities that transformed the region to its current savanna/forest/wetland mosaic beginning at least 3,500 y ago. Regional environmental variables did not drive the choices made by farmers and fishers, who shaped these local contexts to better manage resource extraction. The savannas we observe today were created in the post-European period, where their fire regime and structural diversity were shaped by cattle ranching

Seasonal and interannual variation in high‑latitude estuarine fsh community structure along a glacial to non‑glacial watershed gradient in Southeast Alaska

Along the Gulf of Alaska, rapid glacier retreat has driven changes in transport of freshwater, sediments, and nutrients to estuary habitats. Over the coming decades, deglaciation will lead to a temporary increase, followed by a long-term decline of glacial influence on estuaries. Therefore, quantifying the current variability in estuarine fish community structure in regions predicted to be most affected by glacier loss is necessary to anticipate future impacts. We analyzed fish community data collected monthly (April through September) over 7 years (2013–2019) from glacially influenced estuaries along the southeastern Gulf of Alaska. River delta sites within estuaries were sampled along a natural gradient of glacial to non-glacial watersheds to characterize variation in fish communities exposed to varying degrees of glacial influence. Differences in seasonal patterns of taxa richness and abundance between the most and least glacially influenced sites suggest that hydrological drivers influence the structure of delta fish communities. The most glacially influenced sites had lower richness but higher abundance overall compared to those with least glacial influence; however, differences among sites were small compared to differences across months. Two dominant species—Pacific staghorn sculpin and starry flounder—contributed most to spatial and temporal variation in community composition; however, given only small interannual differences in richness and abundance over the period of the study, we conclude that year-to-year variation at these sites is relatively low at present. Our study provides an important benchmark against which to compare shifts in fish communities as watersheds and downstream estuaries continue to transform in the coming decades.This research was funded by the Alaska Established Program to Stimulate Competitive Research (EPSCoR) National Science Foundation award no. OIA-1208927 and award no. OIA-1757348 and by the State of Alaska. In addition, this publication is the result of research sponsored by Alaska Sea Grant with funds from the National Oceanic and Atmospheric Administration Ofce of Sea Grant, Department of Commerce, under grant no. NA14OAR4170079 (projects RR/14-01 & R/32-07 to AHB) and G00009215 (project 14CR-07 to CAB), and from the University of Alaska with funds appropriated by the state. Student support was also provided to DHD through a Ladd Macaulay Graduate Fellowship in Salmon Fisheries Research funded through an endowment and donations provided to the University of Alaska by Douglas Island Pink and Chum, Inc. (DIPAC), and to NCL by the North Pacifc Research Board through a Graduate Student Research Award. We are grateful to Franz Mueter for assistance with the analysis and to the many students and volunteers who participated in feldwork. Thanks to two anonymous reviewers whose comments improved the paper. This research was approved by the University of Alaska Institutional Animal Care and Use Committee (protocols 465729, 880562, 479533, 1238650).Ye