ABOUT THE COLLECTIONS

These collections include publications and data from University of Arizona faculty, staff and researchers. The UA Faculty Publications collection consists primarily of open access versions of published journal articles, but also contains conference proceedings and other unique materials from faculty, staff and researchers. Organizational collections, such as the College of Agricultural and Life Sciences Publications, and Water Resources Research Center, contain additional faculty publications such as departmentally produced technical bulletins, technical reports, and working papers.

QUESTIONS?

Please contact the Office of Digital Innovation & Stewardship at repository@u.library.arizona.edu with questions or comments about items in these collections, or if you are affiliated with the University of Arizona and are interested in adding content to the UA Campus Repository. We look forward to working with you.

Sub-communities within this community

Collections in this community

Recent Submissions

  • Elongation during segmentation shows axial variability, low mitotic rates, and synchronized cell cycle domains in the crustacean, Thamnocephalus platyurus

    Constantinou, Savvas J; Duan, Nicole; Nagy, Lisa M; Chipman, Ariel D; Williams, Terri A; Univ Arizona, Dept Mol & Cellular Biol (BMC, 2020-01-18)
    Using precisely staged larvae of the crustacean, Thamnocephalus platyurus, we systematically examine cell division patterns and morphometric changes associated with posterior elongation during segmentation. We show that cell division occurs during normal elongation but that cells in the growth zone need only divide ~ 1.5 times to meet growth estimates; correspondingly, direct measures of cell division in the growth zone are low. Morphometric measurements of the growth zone and of newly formed segments suggest tagma-specific features of segment generation. Using methods for detecting two different phases in the cell cycle, we show distinct domains of synchronized cells in the posterior trunk. Borders of cell cycle domains correlate with domains of segmental gene expression, suggesting an intimate link between segment generation and cell cycle regulation.
  • Revisiting the Weberian Presumption: Gun Militarism, Gun Populism, and the Racial Politics of Legitimate Violence in Policing

    Carlson, Jennifer; Univ Arizona (University of Chicago Press, 2019-11-01)
    Focusing on police chiefs in three states, this study revisits the Weberian presumption of the state's monopoly on legitimate violence. Seventy-nine interviews with police chiefs in Arizona, Michigan, and California allow for an examination of their understanding of gun policy. Analysis reveals that they selectively embrace two frames of the state's relationship with legitimate violence: gun militarism for criminal gun activity associated with black and brown communities and drug- and gang-related crime and gun populism with respect to lawfully gun-owning Americans, often marked as white and middle class. Sensitive to state-level sociolegal regimes, gun populism takes the form of antielitism in gun-restrictive California, crime-fighting by proxy in gun-permissive Michigan, and co-policing in gun-lax Arizona. The racial politics of legitimate violence intersect with state-level gun policies selectively to erode police chiefs' investment in the state's monopoly on violence, demonstrating that gun politics is pertinent not only for understanding violence in the United States but also for understanding the racial complexity of U.S. policing.
  • Effects of sampling rate and type of anti-aliasing filter on linear-predictive estimates of formant frequencies in men, women, and children

    Milenkovic, Paul H.; Wagner, Madison; Kent, Raymond D.; Story, Brad H.; Vorperian, Houri K.; Univ Arizona, Speech Language & Hearing Sci (ACOUSTICAL SOC AMER AMER INST PHYSICS, 2020-03-04)
    The purpose of this study was to assess the effect of downsampling the acoustic signal on the accuracy of linear-predictive (LPC) formant estimation. Based on speech produced by men, women, and children, the first four formant frequencies were estimated at sampling rates of 48, 16, and 10 kHz using different anti-alias filtering. With proper selection of number of LPC coefficients, anti-alias filter and between-frame averaging, results suggest that accuracy is not improved by rates substantially below 48 kHz. Any downsampling should not go below 16 kHz with a filter cut-off centered at 8 kHz. (C) 2020 Acoustical Society of America
  • Impact of Intensity Standards on Alternative Fuel Adoption: Renewable Natural Gas and California's Low Carbon Fuel Standard

    Scheitrum, Daniel; Univ Arizona, Dept Agr & Resource Econ (INT ASSOC ENERGY ECONOMICS, 2020-04-01)
    Natural gas is a rapidly growing transportation fuel. While fossil natural gas is only slightly cleaner than conventional fuels, it provides a vector to introduce renewable natural gas (RNG) which can yield substantial emissions reductions. This paper considers RNG supply estimates from four possible sources: dairy manure, municipal solid waste, wastewater treatment plants, and landfill gas along with other major transportation fuels to evaluate the impact of California's Low Carbon Fuel Standard (LCFS) a first of its kind fuel intensity standard. A static, multi-market, partial equilibrium, numerical model of the California fuel markets assesses the economic surplus and climate impact responses to the LCFS policy and compares the efficiency of the LCFS to a hypothetical carbon tax. Results indicate LCFS policy is sufficient to incentivize substantial quantities of RNG production. The LCFS approaches the efficiency of a carbon tax as the LCFS policy becomes more stringent when combined with a price ceiling.
  • Smartphone based on-chip fluorescence imaging and capillary flow velocity measurement for detecting ROR1+ cancer cells from buffy coat blood samples on dual-layer paper microfluidic chip

    Ulep, Tiffany-Heather; Zenhausern, Ryan; Gonzales, Alana; Knoff, David S; Lengerke Diaz, Paula A; Castro, Januario E; Yoon, Jeong-Yeol; Univ Arizona, Dept Biomed Engn (ELSEVIER ADVANCED TECHNOLOGY, 2020-01-22)
    Diagnosis of hematological cancer requires complete white blood cell count, followed by flow cytometry with multiple markers, and cytology. It requires substantial time and specialized training. A dual-layer paper microfluidic chip was developed as a quicker, low-cost, and field-deployable alternative to detect ROR1+ (receptor tyrosine-like orphan receptor one) cancer cells from the undiluted and untreated buffy coat blood samples. The first capture layer consisted of a GF/D glass fiber substrate, preloaded with cancer specific anti-ROR1 conjugated fluorescent particles to its center for cancer cell capture and direct smartphone fluorescence imaging. The second flow layer was comprised of a grade 1 cellulose chromatography paper with wax-printed four channels for wicking and capillary flow-based detection. The flow velocity was used as measure of antigen concentration in the buffy coat sample. In this manner, intact cells and their antigens were separated and independently analyzed by both imaging and flow velocity analyses. A custom-made smartphone-based fluorescence microscope and automated image processing and particle counter software were developed to enumerate particles on paper, with the limit of detection of 1 cell/mu L. Flow velocity analysis showed even greater sensitivity, with the limit of detection of 0.1 cells/mu L in the first 6 s of assay. Comparison with capillary flow model revealed great alignment with experimental data and greater correlation to viscosity than interfacial tension. Our proposed device Is able to capture and on-chip image ROR1+ cancer cells within a complex sample matrix (buffy coat) while simultaneously quantifying cell concentration in a point-of-care manner.
  • A Carbohydrate Beverage Reduces Monocytes Expressing TLR4 in Children with Overweight or Obesity

    Niemiro, Grace M; Chiarlitti, Nathan A; Khan, Naiman A; De Lisio, Michael; Univ Arizona, Coll Med, Dept Pediat (OXFORD UNIV PRESS, 2020-03)
    Background: Childhood obesity is increasing, with about one-third of children overweight or obese. Obesity is characterized by a state of chronic low-grade inflammation that is related to cardiometabolic comorbidities. Inflammatory monocytes, which are classified into 3 different groups-classical, intermediate, and nonclassical monocytes, with Toll-like receptor 4 (TLR4(+)) expression indicating a proinflammatory state-underlie several obesity-associated morbidities. Objectives: This study aimed to assess the responses of monocyte populations to beverages of differing macronutrient composition in children with healthy weight (HW) or overweight/obesity (OW/OB). Methods: Ten HW children (5th to 84.9th percentile; mean age 12.29 +/- 2.5 y) and 7 children with OW/OB (85th to 99.99th percentile; mean age 11.96 +/- 3.8 y) completed the study. Adiposity was determined via DXA. Using a doubleblinded, randomized, crossover design, participants consumed either a high-carbohydrate (CHO; 210 kcal; 0 g fat/56 g carbohydrates/0 g protein) or a whole-egg-based high-protein/fat (EGG; 210 kcal; 15 g fat/0 g carbohydrates/18 g protein) beverage. Venous blood was collected at baseline and 2 h postprandially for evaluation of metabolic and inflammatory responses. Repeated measures ANOVA and Pearson correlations were conducted. Results: Consuming the CHO beverage significantly reduced the primary outcome: TLR4(+) expression on classical monocytes in children with OW/OB only (25.60% decrease from baseline in OW/OB compared with 1.61% increase in HW). Children with OW/OB had significantly less percentages of TLR4(+) nonclassical monocytes than HW (4766% lower after CHO). Insulin and glucose (secondary outcomes), were significantly higher after the CHO condition compared with baseline (230.61% and 9.93% increase, respectively). Changes in glucose were significantly and negatively related to changes in monocyte populations in the CHO condition. Conclusions: These data suggest that high-carbohydrate beverages alter monocyte populations in the blood in children with OW/OB, which is related to glucose metabolism. These findings have implications for nutritional recommendations in children with overweight/obesity.
  • Effect of exogenous progesterone administration on cigarette smoking-related symptomology in oral contraceptive users who smoke

    Harrison, Katherine; Petersen, Ashley; Tosun, Nicole; Crist, Katherine; Allen, Alicia M; Allene, Sharon; Univ Arizona, Dept Family & Community Med (PERGAMON-ELSEVIER SCIENCE LTD, 2020-03)
    Cigarette smoking-related symptomatology (e.g., craving; SRS) is linked to relapse after a quit attempt. SRS varies by menstrual phase, possibly due to variations in sex hormones (e.g., progesterone), though much of the research to-date has relied on observations from the menstrual cycle acting as a proxy for hormone levels. The goal of this study was to examine the effect of exogenous progesterone on SRS during ad libitum smoking and following overnight abstinence. Oral contraceptive users who smoked completed two 9-day crossover testing periods (7 days of ad libitum smoking and 2 days following overnight abstinence) while taking double-blind active/placebo exogenous progesterone. Participants completed questionnaires to measure SRS. The effect of exogenous progesterone and endogenous hormones (progesterone, estradiol, and progesterone-to-estradiol [P/E2] ratio) on SRS was assessed with paired t-tests and linear mixed effect models. Participants (n = 53) were, on average, 24 years old and smoked 11 cigarettes per day. During ad libitum smoking, a doubling of the P/E2 ratio was associated with 0.09 points lower anticipated relief from negative affect (95% confidence interval [CI]: 0.03-0.15 points lower; p = 0.008) and 0.11 points lower psychological reward (95% CI: 0.03-0.18 points lower; p = 0.006). After correction for multiple testing, these associations were not statistically significant: anticipated relief from negative effect (p = 0.10) and psychological reward (p = 0.09). No other significant associations were observed. Although substantial previous literature indicates that progesterone influences SRS, exogenous progesterone administration did not alter SRS here. Additional research is needed to elucidate alternative mechanisms involved in menstrual phase effects on SRS.
  • Flash droughts present a new challenge for subseasonal-to-seasonal prediction

    Pendergrass, Angeline G.; Meehl, Gerald A.; Pulwarty, Roger; Hobbins, Mike; Hoell, Andrew; AghaKouchak, Amir; Bonfils, Céline J. W.; Gallant, Ailie J. E.; Hoerling, Martin; Hoffmann, David; et al. (NATURE PUBLISHING GROUP, 2020-03)
    Flash droughts, which develop over the course of weeks, are difficult to forecast given the current state of subseasonal-to-seasonal prediction. This Perspective offers operational and research definitions, places them in the broader context of climate and suggests avenues for future research. Flash droughts are a recently recognized type of extreme event distinguished by sudden onset and rapid intensification of drought conditions with severe impacts. They unfold on subseasonal-to-seasonal timescales (weeks to months), presenting a new challenge for the surge of interest in improving subseasonal-to-seasonal prediction. Here we discuss existing prediction capability for flash droughts and what is needed to establish their predictability. We place them in the context of synoptic to centennial phenomena, consider how they could be incorporated into early warning systems and risk management, and propose two definitions. The growing awareness that flash droughts involve particular processes and severe impacts, and probably a climate change dimension, makes them a compelling frontier for research, monitoring and prediction.
  • On the Gibbs–Wilbraham Phenomenon for Sampling and Interpolatory Series

    Hamm, Keaton; Univ Arizona, Dept Math (CAMBRIDGE UNIV PRESS, 2019-11)
    We investigate the Gibbs-Wilbraham phenomenon for generalized sampling series, and related interpolation series arising from cardinal functions. We prove the existence of the overshoot characteristic of the phenomenon for certain cardinal functions, and characterize the existence of an overshoot for sampling series.
  • Perspectives on CUR decompositions

    Hamm, Keaton; Huang, Longxiu; Univ Arizona, Dept Math (ACADEMIC PRESS INC ELSEVIER SCIENCE, 2020-05)
    This note discusses an interesting matrix factorization called the CUR Decomposition. We illustrate various viewpoints of this method by comparing and contrasting them in different situations. Additionally, we offer a new characterization of CUR decompositions which synergizes these viewpoints and shows that they are indeed the same in the exact decomposition case. (C) 2019 Elsevier Inc. All rights reserved.
  • The forgotten land use class: Mapping of fallow fields across the Sahel using Sentinel-2

    Tong, Xiaoye; Brandt, Martin; Hiernaux, Pierre; Herrmann, Stefanie; Rasmussen, Laura Vang; Rasmussen, Kjeld; Tian, Feng; Tagesson, Torbern; Zhang, Wenmin; Fensholt, Rasmus; et al. (ELSEVIER SCIENCE INC, 2020-03-15)
    Remote sensing-derived cropland products have depicted the location and extent of agricultural lands with an ever increasing accuracy. However, limited attention has been devoted to distinguishing between actively cropped fields and fallowed fields within agricultural lands, and in particular so in grass fallow systems of semi-arid areas. In the Sahel, one of the largest dryland regions worldwide, crop-fallow rotation practices are widely used for soil fertility regeneration. Yet, little is known about the extent of fallow fields since fallow is not explicitly differentiated within the cropland class in any existing remote sensing-based land use/cover maps, regardless of the spatial scale. With a 10 m spatial resolution and a 5-day revisit frequency, Sentinel-2 satellite imagery made it possible to disentangle agricultural land into cropped and fallow fields, facilitated by Google Earth Engine (GEE) for big data handling. Here we produce the first Sahelian fallow field map at a 10 m resolution for the baseline year 2017, accomplished by designing a remote sensing driven protocol for generating reference data for mapping over large areas. Based on the 2015 Copernicus Dynamic Land Cover map at 100 m resolution, the extent of fallow fields in the cropland class is estimated to be 63% (403,617 km(2)) for the Sahel in 2017. Similar results are obtained for five contemporary cropland products, with fallow fields occupying 57-62% of the cropland area. Yet, it is noted that the total estimated area coverage depends on the quality of the different cropland products. The share of cropped fields within the Copernicus cropland area is found to be higher in the arid regions (200-300 mm rainfall) as compared to the semi-arid regions (300-600 mm rainfall). The woody cover fraction within cropped and fallow fields is found to have a reversed pattern between arid (higher woody cover in cropped fields) and semi-arid (higher woody cover in fallow fields) regions. The method developed, using cloud-based Earth Observation (EO) data and computation on the GEE platform, is expected to be reproducible for mapping the extent of fallow fields across global croplands. Future applications based on multi-year time series is expected to improve our understanding of crop-fallow rotation dynamics in grass fallow systems being key in teasing apart how cropland intensification and expansion affect environmental variables, such as soil fertility, crop yields and local livelihoods in low-income regions such as the Sahel.
  • “Mom, I want to come home”: Geographies of compound displacement, violence and longing

    Myadar, Orhon; Davidson, Ronald A.; Univ Arizona, Sch Geog & Dev (PERGAMON-ELSEVIER SCIENCE LTD, 2020-02)
    This article focuses on former "comfort woman" Gil Won-ok's story to explore the dialectical relationship between place and self, or what Edward Casey calls the "geographical self." Gil was one of thousands of women who were used as sex slaves by the Imperial Army of Japan at "comfort stations" during World War II. Taken from her hometown of Pyongyang when she was fourteen years old, Gil endured years of compounding violence in displacement away from her family and homeland. Today, at age 92, Gil still does not know what happened to her family as the division of Korea prevented her from returning home, extending her displacement. Despite the scale and brutal nature of this state-sponsored violence against thousands of young women and girls, geographic scholarship is critically lacking in addressing this violence. We hope to fill this gap. Theoretically, the article contributes to the broader literature on the dyad of place and self, and we do so by broadening the discussion of the geographical self to better understand the violence of displacement and longing for one's lost place. But most importantly this article would make a modest contribution of recognition to Gil's long struggle and perseverance.
  • Visions of a Martian future

    Szocik, Konrad; Abood, Steven; Impey, Chris; Shelhamer, Mark; Haqq-Misra, Jacob; Persson, Erik; Oviedo, Lluis; Capova, Klara Anna; Braddock, Martin; Rappaport, Margaret Boone; et al. (ELSEVIER SCI LTD, 2020-03)
    As we look beyond our terrestrial boundary to a multi-planetary future for humankind, it becomes paramount to anticipate the challenges of various human factors on the most likely scenario for this future: permanent human settlement of Mars. Even if technical hurdles are circumvented to provide adequate resources for basic physiological and psychological needs, Homo sapiens will not survive on an alien planet if a dysfunctional psyche prohibits the utilization of these resources. No matter how far we soar into the stars, our psychologies for future generations will be forever tethered to the totality of our surroundings. By shaping our environment toward survival and welfare during the voyage to Mars and in a Martian colony, we indirectly shape our psyches and prepare them for a mission of unprecedented alienation and duration. Once on Mars, human factors such as leadership structure, social organization and code of conduct, group size, gender balance, developmental cycle, mobility, length of stay and the ecological settings and type and manner of subsistence, will create a novel Martian culture. The degree that settlers are severed from the Earth will affect how radically foreign this culture will be when compared with cultures on Earth.
  • On Ways of Studying Tolkien: Notes Toward a Better (Epic) Fantasy Criticism

    Wise, Dennis Wilson; Univ Arizona (Valparaiso University, 2020)
    This article examines major academic approaches used in the study of J.R.R. Tolkien. It argues that certain themes from political philosopher Leo Strauss, by helping us to develop a new theoretical lens, can elucidate several politically salient aspects of Tolkien's work, including thymos and his dialectic between ancient and modern. Four previous (though flawed) Straussian interpretations of Tolkien are highlighted. Finally, by analyzing the tensions that arise when pairing critical theory and its attendant bias against nature with Tolkien and epic fantasy, this article argues for the timeliness of a Straussian lens for studying fantasy and Tolkien alike.
  • The Image of Law in Stephen R. Donaldson’s “Reave the Just”: Agency, Blame, and Sexual Assault

    Wise, Dennis Wilson; Univ Arizona (ROUTLEDGE JOURNALS, TAYLOR & FRANCIS LTD, 2020-03-10)
    Stephen R. Donaldson is a major modern writer of speculative fiction for whom the issue of sexed violence, including rape, plays an important role. This article examines "Reave the Just," the keynote story in his award-winning collection Reave the Just and Other Tales, as a gateway into how Donaldson examines sexed violence in his long-form fiction. While the story reflects a strong feminist commitment to gender equality and individual agency, I argue that Donaldson's liberal individualist conception of the law, which retains wide contemporary cultural and juridical support, has also become problematized through recent radical and postmodern feminist discussions on victim blaming. After assessing the strengths and weaknesses of the liberal position articulated by "Reave," I suggest that Donaldson's story helps revive a link between agency and victimization-first advanced by second wave feminists-that, by the time of the story's composition in the 1990s, had generally lost feminist support.
  • Salience, Myopia, and Complex Dynamic Incentives: Evidence from Medicare Part D

    Dalton, Christina M; Gowrisankaran, Gautam; Town, Robert J; Univ Arizona (OXFORD UNIV PRESS, 2020-03)
    The standard Medicare Part D drug insurance contract is non-linear-with reduced subsidies in a coverage gap-resulting in a dynamic purchase problem. We consider enrolees who arrived near the gap early in the year and show that they should expect to enter the gap with high probability, implying that, under a benchmark model with neoclassical preferences, the gap should impact them very little. We find that these enrolees have flat spending in a period before the doughnut hole and a large spending drop in the gap, providing evidence against the benchmark model. We structurally estimate behavioural dynamic drug purchase models and find that a price salience model where enrolees do not incorporate future prices into their decision-making at all fits the data best. For a nationally representative sample, full price salience would decrease enrolee spending by 31%. Entirely eliminating the gap would increase insurer spending 27%, compared to 7% for generic-drug-only gap coverage.
  • Impact of Space Weather on the Natural Night Sky

    Grauer, Albert D.; Grauer, Patricia A.; Davies, Nalayini; Davies, Gareth; Univ Arizona, Lunar & Planetary Lab, Catalina Sky Survey (IOP PUBLISHING LTD, 2019-11)
    In 2018, Solar Cycle 24 entered a deep solar minimum. During this period, we collected night sky brightness data at Cosmic Campground International Dark Sky Sanctuary (CCIDSS) in the USA (2018 September 4-2019 January 4) and at Aotea/Great Barrier Island International Dark Sky Sanctuary (AGBIIDSS) in New Zealand (2018 March 26-August 31. These sites have artificial-light-pollution-free natural night skies. The equipment employed are identical Unihedron SQM-LU-DL meters, used as single-channel differential photometers, to scan the sky as Earth rotates on its axis. We have developed new analysis techniques which select those data points which are uninfluenced by Sun, Moon, or clouds to follow brightness changes at selected points on the celestial sphere and to measure the brightness of the airglow above its quiescent level. The 2018 natural night sky was measured to change in brightness by approximately 0.9 mag arcsec(-2) at both locations. Preliminary results indicate the modulations of the light curves (brightness versus R.A.) we observed are related in complex ways to elements of space weather conditions in the near-Earth environment. In particular, episodes of increased night sky brightness are observed to be contemporaneous with geomagnetic activity, increases in mean solar wind speed, and some solar proton/electron fluence events. Charged particles in the solar wind take days to reach near-Earth environment after a coronal hole is observed to be facing in our direction. Use of this information could make it possible to predict increases in Earth's natural night sky brightness several days in advance. What we have learned during this solar minimum leads us to search for other solar driven changes in night sky brightness as the Sun begins to move into solar maximum conditions.
  • Inferring the parallax of Westerlund 1 from Gaia DR2

    Aghakhanloo, Mojgan; Murphy, Jeremiah W; SMITH, NATHAN; Parejko, John; Díaz-Rodríguez, Mariangelly; Drout, Maria R; Groh, Jose H; Guzman, Joseph; Stassun, Keivan G; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2019-12-31)
    Westerlund 1 (Wd1) is potentially the largest star cluster in the Galaxy. That designation critically depends upon the distance to the cluster, yet the cluster is highly obscured, making luminosity-based distance estimates difficult. Using Gaia Data Release 2 (DR2) parallaxes and Bayesian inference, we infer a parallax of 0.35(-0.06)(+0.07) mas corresponding to a distance of 2.6(-0.4)(+0.6) kpc. To leverage the combined statistics of all stars in the direction of Wd1, we derive the Bayesian model for a cluster of stars hidden among Galactic field stars; this model includes the parallax zero-point. Previous estimates for the distance to Wd1 ranged from 1.0 to 5.5 kpc, although values around 5 kpc have usually been adopted. The Gaia DR2 parallaxes reduce the uncertainty from a factor of 3 to 18 per cent and rules out the most often quoted value of 5 kpc with 99 per cent confidence. This new distance allows for more accurate mass and age determinations for the stars in Wd1. For example, the previously inferred initial mass at the main-sequence turn-off was around 40 M-circle dot; the new Gaia DR2 distance shifts this down to about 22 M-circle dot. This has important implications for our understanding of the late stages of stellar evolution, including the initial mass of the magnetar and the LBV in Wd1. Similarly, the new distance suggests that the total cluster mass is about four times lower than previously calculated.
  • Are inner disc misalignments common? ALMA reveals an isotropic outer disc inclination distribution for young dipper stars

    Ansdell, M; Gaidos, E; Hedges, C; Tazzari, M; Kraus, A L; Wyatt, M C; Kennedy, G M; Williams, J P; Mann, A W; Angelo, I; et al. (OXFORD UNIV PRESS, 2019-12-02)
    Dippers are a common class of young variable star exhibiting day-long dimmings with depths of up to several tens of per cent. A standard explanation is that dippers host nearly edge-on (i(d) approximate to 70 degrees) protoplanetary discs that allow close-in (<1 au) dust lifted slightly out of the mid-plane to partially occult the star. The identification of a face-on dipper disc and growing evidence of inner disc misalignments brings this scenario into question. Thus, we uniformly (re)derive the inclinations of 24 dipper discs resolved with (sub-)mm interferometry from ALMA. We find that dipper disc inclinations are consistent with an isotropic distribution over i(d) approximate to 0-75 degrees, above which the occurrence rate declines (likely an observational selection effect due to optically thick disc mid-planes blocking their host stars). These findings indicate that the dipper phenomenon is unrelated to the outer (>10 au) disc resolved by ALMA and that inner disc misalignments may be common during the protoplanetary phase. More than one mechanism may contribute to the dipper phenomenon, including accretion-driven warps and 'broken' discs caused by inclined (sub-)stellar or planetary companions.
  • The case for strangulation in low-mass hosts: DDO 113

    Garling, Christopher T; Peter, Annika H G; Kochanek, Christopher S; Sand, David J; Crnojević, Denija; Univ Arizona, Dept Astron; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2019-12-24)
    We investigate the case for environmental quenching of the Fornax-mass satellite DDO 113, which lies only 9 kpc in projection from its host, the Large-Magellanic-Cloud-mass galaxy NGC 4214. DDO 113 was quenched about 1 Gyr ago and is virtually gas-free, while analogs in the field are predominantly star-forming and gas-rich. We use deep imaging obtained with the Large Binocular Telescope to show that DDO 113 exhibits no evidence of tidal disruption to a surface brightness of μV ∼ 29 mag arcsec−2, based on both unresolved emission and resolved stars. Mass-analogs of DDO 113 in Illustris-1 with similar hosts, small projected separations, and no significant tidal stripping first fell into their host halo 2–6 Gyr ago, showing that tidal features (or lack thereof) can be used to constrain infall times in systems where there are few other constraints on the orbit of the satellite. With the infall time setting the clock for environmental quenching mechanisms, we investigate the plausibility of several such mechanisms. We find that strangulation, the cessation of cold gas inflows, is likely the dominant quenching mechanism for DDO 113, requiring a time-averaged mass-loading factor of η = 6–11 for star-formation-driven outflows that is consistent with theoretical and observational constraints. Motivated by recent numerical work, we connect DDO 113’s strangulation to the presence of a cool circumgalactic medium (CGM) around NGC 4214. This discovery shows that the CGM of low-mass galaxies can affect their satellites significantly and motivates further work on understanding the baryon cycle in low-mass galaxies.

View more