Now showing items 1-20 of 81954

    • Mass–Metallicity Trends in Transiting Exoplanets from Atmospheric Abundances of H2O, Na, and K

      Welbanks, Luis; Madhusudhan, Nikku; Allard, Nicole F.; Hubeny, Ivan; Spiegelman, Fernand; Leininger, Thierry; Univ Arizona, Dept Astron (IOP PUBLISHING LTD, 2019-12-11)
      Atmospheric compositions can provide powerful diagnostics of formation and migration histories of planetary systems. We investigate constraints on atmospheric abundances of H2O, Na, and K, in a sample of transiting exoplanets using the latest transmission spectra and new H-2 broadened opacities of Na and K. Our sample of 19 exoplanets spans from cool mini-Neptunes to hot Jupiters, with equilibrium temperatures between similar to 300 and 2700 K. Using homogeneous Bayesian retrievals we report atmospheric abundances of Na, K, and H2O, and their detection significances, confirming 6 planets with strong Na detections, 6 with K, and 14 with H2O. We find a mass-metallicity trend of increasing H2O abundances with decreasing mass, spanning generally substellar values for gas giants and stellar/superstellar for Neptunes and mini-Neptunes. However, the overall trend in H2O abundances, from mini-Neptunes to hot Jupiters, is significantly lower than the mass-metallicity relation for carbon in the solar system giant planets and similar predictions for exoplanets. On the other hand, the Na and K abundances for the gas giants are stellar or superstellar, consistent with each other, and generally consistent with the solar system metallicity trend. The H2O abundances in hot gas giants are likely due to low oxygen abundances relative to other elements rather than low overall metallicities, and provide new constraints on their formation mechanisms. The differing trends in the abundances of species argue against the use of chemical equilibrium models with metallicity as one free parameter in atmospheric retrievals, as different elements can be differently enhanced.
    • Drill core data for the Courtland-Gleeson area, Turquoise mining district and southern Dragoon Mountains, Cochise County, Arizona

      Richardson, C.A.; Arizona Geological Survey (Arizona Geological Survey (Tucson, AZ), 2020)
    • Constraining the Neutron Star Mass–Radius Relation and Dense Matter Equation of State with NICER. I. The Millisecond Pulsar X-Ray Data Set

      Bogdanov, Slavko; Guillot, Sebastien; Ray, Paul S.; Wolff, Michael T.; Chakrabarty, Deepto; Ho, Wynn C. G.; Kerr, Matthew; Lamb, Frederick K.; Lommen, Andrea; Ludlam, Renee M.; et al. (IOP PUBLISHING LTD, 2019-12-12)
      Atmospheric compositions can provide powerful diagnostics of formation and migration histories of planetary systems. We investigate constraints on atmospheric abundances of H2O, Na, and K, in a sample of transiting exoplanets using the latest transmission spectra and new H-2 broadened opacities of Na and K. Our sample of 19 exoplanets spans from cool mini-Neptunes to hot Jupiters, with equilibrium temperatures between similar to 300 and 2700 K. Using homogeneous Bayesian retrievals we report atmospheric abundances of Na, K, and H2O, and their detection significances, confirming 6 planets with strong Na detections, 6 with K, and 14 with H2O. We find a mass-metallicity trend of increasing H2O abundances with decreasing mass, spanning generally substellar values for gas giants and stellar/superstellar for Neptunes and mini-Neptunes. However, the overall trend in H2O abundances, from mini-Neptunes to hot Jupiters, is significantly lower than the mass-metallicity relation for carbon in the solar system giant planets and similar predictions for exoplanets. On the other hand, the Na and K abundances for the gas giants are stellar or superstellar, consistent with each other, and generally consistent with the solar system metallicity trend. The H2O abundances in hot gas giants are likely due to low oxygen abundances relative to other elements rather than low overall metallicities, and provide new constraints on their formation mechanisms. The differing trends in the abundances of species argue against the use of chemical equilibrium models with metallicity as one free parameter in atmospheric retrievals, as different elements can be differently enhanced.
    • The Acceleration and Confinement of Energetic Electrons by a Termination Shock in a Magnetic Trap: An Explanation for Nonthermal Loop-top Sources during Solar Flares

      Kong, Xiangliang; Guo, Fan; Shen, Chengcai; Chen, Bin; Chen, Yao; Musset, Sophie; Glesener, Lindsay; Pongkitiwanichakul, Peera; Giacalone, Joe; Univ Arizona, Dept Planetary Sci (IOP PUBLISHING LTD, 2019-12-20)
      We present the set of deep Neutron Star Interior Composition Explorer (NICER) X-ray timing observations of the nearby rotation-powered millisecond pulsars PSRs J0437-4715, J0030+0451, J1231-1411, and J2124-3358, selected as targets for constraining the mass-radius relation of neutron stars and the dense matter equation of state (EoS) via modeling of their pulsed thermal X-ray emission. We describe the instrument, observations, and data processing/reduction procedures, as well as the series of investigations conducted to ensure that the properties of the data sets are suitable for parameter estimation analyses to produce reliable constraints on the neutron star mass-radius relation and the dense matter EoS. We find that the long-term timing and flux behavior and the Fourier-domain properties of the event data do not exhibit any anomalies that could adversely affect the intended measurements. From phase-selected spectroscopy, we find that emission from the individual pulse peaks is well described by a single-temperature hydrogen atmosphere spectrum, with the exception of PSR J0437-4715, for which multiple temperatures are required.
    • Physical Characterization of the 2017 December Outburst of the Centaur 174P/Echeclus

      Kareta, Theodore; Sharkey, Benjamin; Noonan, John; Volk, Kat; Reddy, Vishnu; Harris, Walter; Miles, Richard; Univ Arizona, Lunar & Planetary Lab (IOP PUBLISHING LTD, 2019-12-04)
      The Centaurs are the small solar system bodies intermediate between the active inner solar system Jupiter family comets and their inactive progenitors in the trans-Neptunian region. Among the fraction of Centaurs which show comet-like activity, 174P/Echeclus is best known for its massive 2005 outburst in which a large apparently active fragment was ejected above the escape velocity from the primary nucleus. We present visible imaging and near-infrared spectroscopy of Echeclus during the first week after its 2017 December outburst taken at the Faulkes North and South Telescopes and the NASA IRTF, the largest outburst since 2005. The coma was seen to be highly asymmetric. A secondary peak was seen in the near-infrared 2D spectra, which is strongly hinted at in the visible images, moving hyperbolically with respect to the nucleus. The retrieved reflectance spectrum of Echelcus is consistent with the unobscured nucleus but becomes bluer when a wider extraction aperture is used. We find that Echeclus's coma is best explained as dominated by large blue dust grains, which agrees with previous work. We also conducted a high-resolution orbital integration of Echeclus's recent evolution and found no large orbital changes that could drive its modern evolution. We interpret the second peak in the visible and near-infrared data sets as a large cloud of larger-than-dust debris ejected at the time of outburst. If Echeclus is typical of the Centaurs, there may be several debris ejection or fragmentation events per year on other Centaurs that are going unnoticed.
    • Spatial linear dark field control and holographic modal wavefront sensing with a vAPP coronagraph on MagAO-X

      Miller, Kelsey; Males, Jared R.; Guyon, Olivier; Close, Laird M.; Doelman, David; Snik, Frans; Por, Emiel; Wilby, Michael J.; Keller, Christoph; Bohlman, Chris; et al. (SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 2019-12-05)
      The Magellan Extreme Adaptive Optics (MagAO-X) Instrument is an extreme AO system coming online at the end of 2019 that will be operating within the visible and near-IR. With state-of-the-art wavefront sensing and coronagraphy, MagAO-X will be optimized for high-contrast direct exoplanet imaging at challenging visible wavelengths, particularly Ha. To enable high-contrast imaging, the instrument hosts a vector apodizing phase plate (vAPP) coronagraph. The vAPP creates a static region of high contrast next to the star that is referred to as a dark hole; on MagAO-X, the expected dark hole raw contrast is similar to 4 x 10(-6). The ability to maintain this contrast during observations, however, is limited by the presence of non-common path aberrations (NCPA) and the resulting quasi-static speckles that remain unsensed and uncorrected by the primary AO system. These quasi-static speckles within the dark hole degrade the high contrast achieved by the vAPP and dominate the light from an exoplanet. The aim of our efforts here is to demonstrate two focal plane wavefront sensing (FPWFS) techniques for sensing NCPA and suppressing quasi-static speckles in the final focal plane. To sense NCPA to which the primary AO system is blind, the science image is used as a secondary wavefront sensor. With the vAPP, a static high-contrast dark hole is created on one side of the PSF, leaving the opposite side of the PSF unocculted. In this unobscured region, referred to as the bright field, the relationship between modulations in intensity and low-amplitude pupil plane phase aberrations can be approximated as linear. The bright field can therefore be used as a linear wavefront sensor to detect small NCPA and suppress quasi-static speckles. This technique, known as spatial linear dark field control (LDFC), can monitor the bright field for aberrations that will degrade the high-contrast dark hole. A second form of FPWFS, known as holographic modal wavefront sensing (hMWFS), is also employed with the vAPP. This technique uses hologram-generated PSFs in the science image to monitor the presence of low-order aberrations. With LDFC and the hMWFS, high contrast across the dark hole can be maintained over long observations, thereby allowing planet light to remain visible above the stellar noise over the course of observations on MagAO-X. Here, we present simulations and laboratory demonstrations of both spatial LDFC and the hMWFS with a vAPP coronagraph at the University of Arizona Extreme Wavefront Control Laboratory. We show both in simulation and in the lab that the hMWFS can be used to sense low-order aberrations and reduce the wavefront error (WFE) by a factor of 3 - 4x. We also show in simulation that, in the presence of a temporally evolving pupil plane phase aberration with 27-nm root-mean-square (RMS) WFE, LDFC can reduce the WFE to 18-nm RMS, resulting in factor of 6 to 10 gain in contrast that is kept stable over time. This performance is also verified in the lab, showing that LDFC is capable of returning the dark hole to the average contrast expected under ideal lab conditions. These results demonstrate the power of the hMWFS and spatial LDFC to improve MagAO-X's high-contrast imaging capabilities for direct exoplanet imaging. (C) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License.
    • Detection of Ionized Calcium in the Atmosphere of the Ultra-hot Jupiter KELT-9b

      Turner, Jake D.; de Mooij, Ernst J. W.; Jayawardhana, Ray; Young, Mitchell E.; Fossati, Luca; Koskinen, Tommi; Lothringer, Joshua D.; Karjalainen, Raine; Karjalainen, Marie; Univ Arizona, Lunar & Planetary Lab (IOP PUBLISHING LTD, 2020-01-03)
      With a dayside temperature in excess of 4500 K, comparable to a mid-K-type star, KELT-9b is the hottest planet known. Its extreme temperature makes KELT-9b a particularly interesting test bed for investigating the nature and diversity of gas giant planets. We observed the transit of KELT-9b at high spectral resolution (R similar to 94,600) with the CARMENES instrument on the Calar Alto 3.5 m telescope. Using these data, we detect for the first time ionized calcium (Ca ii triplet) absorption in the atmosphere of KELT-9b; this is the second time that Ca ii has been observed in a hot Jupiter. Our observations also reveal prominent H alpha absorption, confirming the presence of an extended hydrogen envelope around KELT-9b. We compare our detections with an atmospheric model and find that all four lines form between atmospheric temperatures of 6100 and 8000 K and that the Ca ii lines form at pressures between 50 and 100 nbar while the H alpha line forms at a lower pressure (similar to 10 nbar), higher up in the atmosphere. The altitude that the core of H alpha line forms is found to be similar to 1.4 R-p, well within the planetary Roche lobe (similar to 1.9 R-p). Therefore, rather than probing the escaping upper atmosphere directly, the H alpha line and the other observed Balmer and metal lines serve as atmospheric thermometers enabling us to probe the planet's temperature profile, thus the energy budget.
    • Rapid Evolution of Volatile CO from the Protostellar Disk Stage to the Protoplanetary Disk Stage

      Zhang, Ke; Schwarz, Kamber R.; Bergin, Edwin A.; Univ Arizona, Lunar & Planetary Lab (IOP PUBLISHING LTD, 2020-03-03)
      Recent observations show that the CO gas abundance, relative to H-2, in many 1-10 Myr old protoplanetary disks may be heavily depleted by a factor of 10-100 compared to the canonical interstellar medium (ISM) value of 10(-4). When and how this depletion happens can significantly affect compositions of planetesimals and atmospheres of giant planets. It is therefore important to constrain whether the depletion occurs already at the earliest protostellar disk stage. Here we present spatially resolved observations of (CO)-O-18, (CO)-O-17, and (CO)-C-13-O-18 J = 2-1 lines in three protostellar disks. We show that the (CO)-O-18 line emits from both the disk and the inner envelope, while (CO)-O-17 and (CO)-C-13-O-18 lines are consistent with a disk origin. The line ratios indicate that both (CO)-O-18 and (CO)-O-17 lines are optically thick in the disk region, and only the (CO)-C-13-O-18 line is optically thin. The line profiles of the (CO)-C-13-O-18 emissions are best reproduced by Keplerian gaseous disks at similar sizes as their mm-continuum emissions, suggesting small radial separations between the gas and mm-sized grains in these disks, in contrast to the large separation commonly seen in protoplanetary disks. Assuming a gas-to-dust ratio of 100, we find that the CO gas abundances in these protostellar disks are consistent with the ISM abundance within a factor of 2, nearly one order of magnitude higher than the average value of 1-10 Myr old disks. These results suggest that there is a fast, similar to 1 Myr, evolution of the abundance of CO gas from the protostellar disk stage to the protoplanetary disk stage.
    • Long-range aerosol transport and impacts on size-resolved aerosol composition in Metro Manila, Philippines

      Braun, Rachel A.; Azadi Aghdam, Mojtaba; Bañaga, Paola Angela; Betito, Grace; Cambaliza, Maria Obiminda; Cruz, Melliza Templonuevo; Lorenzo, Genevieve Rose; MacDonald, Alexander B.; Simpas, James Bernard; Stahl, Connor; et al. (COPERNICUS GESELLSCHAFT MBH, 2020-02-28)
      This study analyzes long-range transport of aerosol and aerosol chemical characteristics based on instances of high- and low-aerosol-loading events determined via ground-based size-resolved aerosol measurements collected at the Manila Observatory in Metro Manila, Philippines, from July to October 2018. Multiple data sources, including models, remote sensing, and in situ measurements, are used to analyze the impacts of long-range aerosol transport on Metro Manila and the conditions at the local and synoptic scales facilitating this transport. Through the use of case studies, evidence of long-range transport of biomass burning aerosol and continental emissions is identified in Metro Manila. Long-range transport of biomass burning aerosol from the Maritime Continent, bolstered by south-westerly flow and permitted by low rainfall, was identified through model results and the presence of biomass burning tracers (e.g., K, Rb) in the ground-based measurements. The impacts of emissions transported from continental East Asia on the aerosol characteristics in Metro Manila are also identified; for one of the events analyzed, this transport was facilitated by the nearby passage of a typhoon. Changes in the aerosol size distributions, water-soluble chemical composition, and contributions of various organic aerosol species to the total water-soluble organic aerosol were examined for the different cases. The events impacted by biomass burning transport had the overall highest concentration of water-soluble organic acids, while the events impacted by long-range transport from continental East Asia showed high percent contributions from shorter-chain dicarboxylic acids (i.e., oxalate) that are often representative of photochemical and aqueous processing in the atmosphere. The low-aerosol-loading event was subject to a larger precipitation accumulation than the high-aerosol events, indicative of wet scavenging as an aerosol sink in the study region. This low-aerosol event was characterized by a larger relative contribution from supermicrometer aerosols and had a higher percent contribution from longer-chain dicarboxylic acids (i.e., maleate) to the water-soluble organic aerosol fraction, indicating the importance of both primary aerosol emissions and local emissions.
    • Nuclear NADPH oxidase-4 associated with disease progression in renal cell carcinoma

      Kaushik, Dharam; Ashcraft, Keith A; Wang, Hanzhang; Shanmugasundaram, Karthigayan; Shah, Pankil K; Gonzalez, Gabriela; Nazarullah, Alia; Tye, Cooper B; Liss, Michael A; Pruthi, Deepak K; et al. (ELSEVIER SCIENCE INC, 2020-05-31)
      Nuclear NADPH oxidase-4 (Nox4) is a key component of metabolic reprogramming and is often overexpressed in renal cell carcinoma (RCC). However, its prognostic role in RCC remains unclear. Here we examined the significance of nuclear Nox4 on disease progression and development of drug resistance in advanced RCC. We analyzed human RCC tissue from multiple regions in the primary index tumor, cancer-associated normal adjacent parenchyma, intravascular tumor in locally advanced cancer patients. We found that the higher nuclear Nox4 expression was significantly associated with progression and death. These findings were consistent after controlling for other competing clinical variables. In contrast, patients with lower nuclear Nox4, even in higher stage RCC had better prognosis. We identified a subset of patients with high nuclear Nox4 who had rapid disease progression or died within 6 months of surgery. In addition, higher nuclear Nox4 level correlated with resistance to targeted therapy and immunotherapy. Western blotting performed on fresh human RCC tissue as well as cell-lines revealed increased nuclear Nox4 expression. Our data support an important prognostic role of Nox4 mediated regulation of RCC independent of other competing variables. Nox4 localizes to the nucleus in high-grade, high-stage RCC. Higher nuclear Nox4 has prognostic significance for disease progression, poor survival, and development of drug resistance in RCC.
    • Social context-dependent singing alters molecular markers of synaptic plasticity signaling in finch basal ganglia Area X

      So, Lisa Y.; Miller, Julie E.; Univ Arizona, Dept Neurosci; Univ Arizona, Dept Speech Language & Hearing Sci (Elsevier BV, 2021-02)
      Vocal communication is a crucial skill required throughout life. However, there is a critical gap in our understanding of the underlying molecular brain mechanisms, thereby motivating our use of the zebra finch songbird model. Adult male zebra finches show differences in neural activity patterns in song-dedicated brain nuclei when they sing in two distinct social contexts: a male singing by himself (undirected, UD) and a male singing to a female (female-directed, FD). In our prior work, we showed that in song-dedicated basal ganglia Area X, protein levels of a N-methyl-D-aspartate receptor subtype 2B (NMDAR2B) increased with more UD song and decreased with more FD song. We hypothesized that molecules downstream of this receptor would show differential protein expression levels in Area X between UD and FD song. Specifically, we investigated calcium/calmodulin dependent protein kinase II beta (CaMKIIB), homer scaffold protein 1 (HOMER1), serine/threonine protein kinase (Akt), and mechanistic target of rapamycin kinase (mTOR) following singing and non-singing states in Area X. We show relationships between social context and protein levels. HOMER1 protein levels decreased with time spent singing FD song, and mTOR protein levels decreased with the amount of and time spent singing FD song. For both HOMER1 and mTOR, there were no differences with the amount of UD song. With time spent singing UD, CaMKIIB protein levels trended in a U-shaped curve whereas Akt protein levels trended down. Both molecules showed no change with FD song. Our results support differential involvement of molecules in synaptic plasticity pathways between UD and FD song behaviors.
    • ATLAS probe for the study of galaxy evolution with 300,000,000 galaxy spectra

      Content, Robert; Wang, Yun; Roberto, Massimo; Dickinson, Mark; Ferguson, Henry; Hillenbrand, Lynne; Fraser, Wesley; Behroozi, Peter; Brinchmann, Jarle; Cimatti, Andrea; et al. (SPIE-INT SOC OPTICAL ENGINEERING, 2018-08-22)
      ATLAS (Astrophysics Telescope for Large Area Spectroscopy) Probe is a mission concept for a NASA probe-class space mission with primary science goal the definitive study of galaxy evolution through the capture of 300,000,000 galaxy spectra up to z=7. It is made of a 1.5-m Ritchey-Chretien telescope with a field of view of solid angle 0.4 deg(2). The wavelength range is at least 1 mu m to 4 mu m with a goal of 0.9 mu m to 5 mu m. Average resolution is 600 but with a possible trade-off to get 1000 at the longer wavelengths. The ATLAS Probe instrument is made of 4 identical spectrographs each using a Digital Micro-mirror Device (DMD) as a multi-object mask. It builds on the work done for the ESA SPACE and Phase-A EUCLID projects. Three-mirror fore-optics re-image each sub-field on its DMD which has 2048 x 1080 mirrors 13.6 mu m wide with 2 possible tilts, one sending light to the spectrograph, the other to a light dump. The ATLAS Probe spectrographs use prisms as dispersive elements because of their higher and more uniform transmission, their larger bandwidth, and the ability to control the resolution slope with the choice of glasses. Each spectrograph has 2 cameras. While the collimator is made of 4 mirrors, each camera is made of only one mirror which reduces the total number of optics. All mirrors are aspheric but with a relatively small P-V with respect to their best fit sphere making them easily manufacturable. For imaging, a simple mirror to replace the prism is not an option because the aberrations are globally corrected by the collimator and camera together which gives large aberrations when the mirror is inserted. An achromatic grism is used instead. There are many variations of the design that permit very different packaging of the optics. ATLAS Probe will enable ground-breaking science in all areas of astrophysics. It will (1) revolutionize galaxy evolution studies by tracing the relation between galaxies and dark matter from the local group to cosmic voids and filaments, from the epoch of reionization through the peak era of galaxy assembly; (2) open a new window into the dark universe by mapping the dark matter filaments to unveil the nature of the dark Universe using 3D weak lensing with spectroscopic redshifts, and obtaining definitive measurements of dark energy and modification of gravity using cosmic large-scale structure; (3) probe the Milky Way's dust-shrouded regions, reaching the far side of our Galaxy; and (4) characterize asteroids and other objects in the outer solar systems.
    • Overview of the Origins Space telescope: science drivers to observatory requirements

      Meixner, Margaret; Armus, Lee; Battersby, Cara; Bauer, James; Bergin, Edwin; Cooray, Asantha; Fortney, Jonathan J.; Kataria, Tiffany; Leisawitz, David T.; Milam, Stefanie N.; et al. (SPIE-INT SOC OPTICAL ENGINEERING, 2018-07-24)
      The Origins Space Telescope (OST) mission concept study is the subject of one of the four science and technology definition studies supported by NASA Headquarters to prepare for the 2020 Astronomy and Astrophysics Decadal Survey. OST will survey the most distant galaxies to discern the rise of metals and dust and to unveil the co-evolution of galaxy and blackhole formation, study the Milky Way to follow the path of water from the interstellar medium to habitable worlds in planetary systems, and measure biosignatures from exoplanets. This paper describes the science drivers and how they drove key requirements for OST Mission Concept 2, which will operate between similar to 5 and similar to 600 microns with a JWST sized telescope. Mission Concept 2 for the OST study optimizes the engineering for the key science cases into a powerful and more economical observatory compared to Mission Concept 1.
    • Kinematic Links and the Coevolution of MHD Winds, Jets, and Inner Disks from a High-resolution Optical [OI] Survey

      Banzatti, Andrea; Pascucci, Ilaria; Edwards, Suzan; Fang, Min; Gorti, Uma; Flock, Mario; Univ Arizona, Dept Planetary Sci; Univ Arizona, Dept Astron (American Astronomical Society, 2019-01-10)
      We present a survey of optical [O I] emission at 6300 angstrom toward 65 T Tauri stars at the spectral resolution of similar to 7 km s(-1). Past work identified a highly blueshifted velocity component (HVC) tracing microjets and a less blueshifted low-velocity component (LVC) attributed to winds. We focus here on the LVC kinematics to investigate links between winds, jets, accretion, and disk dispersal. We track the behavior of four types of LVC components: a broad and a narrow component ("BC" and "NC," respectively) in LVCs that are decomposed into two Gaussians which typically have an HVC, and single-Gaussian LVC profiles separated into those that have an HVC ("SCJ") and those that do not ("SC"). The LVC centroid velocities and line widths correlate with the HVC EW and accretion luminosity, suggesting that LVC/winds and HVC/jets are kinematically linked and connected to accretion. The deprojected HVC velocity correlates with accretion luminosity, showing that faster jets come with higher accretion. BC and NC kinematics correlate, and their blueshifts are maximum at similar to 35 degrees, suggesting a conical wind geometry with this semi-opening angle. Only SCs include n(13-31) up to similar to 3, and their properties correlate with this infrared index, showing that [O I] emission recedes to larger radii as the inner dust is depleted, tracing less dense/hot gas and a decrease in wind velocity. Altogether, these findings support a scenario where optically thick, accreting inner disks launch radially extended MHD disk winds that feed jets, and where inner disk winds recede to larger radii and jets disappear in concert with dust depletion.
    • Geographical context of forgotten amphibians: Colombian "Data Deficient species" sensu IUCN

      Román Palacios, Cristian; Valencia Zuleta, Alejandro; Univ Arizona, Dept Ecol & Evolutionary Biol (REVISTA DE BIOLOGIA TROPICAL, 2018-07-04)
      Whereas more than 10% of global amphibian richness is known to occur in Colombia, almost 16% of these species are currently classified as Data Deficient according to the IUCN. These estimates suggest that the available data for a large portion of amphibians occurring in Colombia is insufficient to assess extinction risk. Here we aim to (1) review the available information on the distribution of the Colombian Data Deficient (DD hereafter) amphibians, (2) analyze their geographic distribution, and (3) evaluate the relationship between anthropogenic impact and their current conservation status. For this, we first compiled geographical records for the DD amphibian species using primary sources. Geographical records were obtained mainly from taxonomic descriptions and non-systematic surveys. We then estimated the geographical range and inferred the potential distribution for each species using letsR and MaxEnt, respectively. We quantified the human footprint for each species and tested the relationship between spatial distribution and anthropogenic change across populations. Analyses are here based on 128 of the 129 DD amphibian species that occur in Colombia. We found that most of these species were recently described and have small geographic ranges. A large proportion of these DD amphibians inhabit the Colombian Andes, and their populations have been strongly affected by human activities. Overall, the spatial clustering suggests that many of these species have faced similar environmental and anthropogenic pressures that have contributed to their rareness. We also suggest that the conservation status for several of the analyzed DD amphibians should be changed to account for the threats they face.
    • Dark energy survey operations: years 4 and 5

      Diehl, H. Thomas; Neilsen, Eric; Gruendl, Robert A.; Abbott, Timothy M. C.; Allam, Sahar; Alvarez, Otto; Annis, James; Balbinot, Eduardo; Bhargava, Sunayana; Bechtol, Keith; et al. (SPIE-INT SOC OPTICAL ENGINEERING, 2018-07-10)
      The Dark Energy Survey (DES) is an operating optical survey aimed at understanding the accelerating expansion of the universe using four complementary methods: weak gravitational lensing, galaxy cluster counts, baryon acoustic oscillations, and Type Ia supernovae. To perform the 5000 sq-degree wide field and 30 sq-degree supernova surveys, the DES Collaboration built the Dark Energy Camera (DECam), a 3 square-degree, 570-Megapixel CCD camera that was installed at the prime focus of the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory (CTIO). DES has completed its third observing season out of a nominal five. This paper describes DES "Year 4" (Y4) and "Year 5" (Y5), the survey strategy, an outline of the survey operations procedures, the efficiency of operations and the causes of lost observing time. It provides details about the quality of these two-season's data, a summary of the overall status, and plans for the final survey season.
    • Planet formation imager: project update

      Monnier, John D.; Ireland, Michael; Kraus, Stefan; Alonso-Herrero, Almudena; Bonsor, Amy; Baron, Fabien; Bayo, Amelia; Berger, Jean-Philippe; Boyajian, Tabetha; Chiavassa, Andrea; et al. (SPIE-INT SOC OPTICAL ENGINEERING, 2018-07-09)
      The Planet Formation Imager (PFI) is a near- and mid-infrared interferometer project with the driving science goal of imaging directly the key stages of planet formation, including the young proto-planets themselves. Here, we will present an update on the work of the Science Working Group (SWG), including new simulations of dust structures during the assembly phase of planet formation and quantitative detection efficiencies for accreting and non-accreting young exoplanets as a function of mass and age. We use these results to motivate two reference PFI designs consisting of a) twelve 3m telescopes with a maximum baseline of 1.2 km focused on young exoplanet imaging and b) twelve 8 m telescopes optimized for a wider range of young exoplanets and protoplanetary disk imaging out to the 150 K H2O ice line. Armed with 4 x 8 m telescopes, the ESO/VLTI can already detect young exoplanets in principle and projects such as MATISSE, Hi-5 and Heimdallr are important PFI pathfinders to make this possible. We also discuss the state of technology development needed to make PFI more affordable, including progress towards new designs for inexpensive, small field-of-view, large aperture telescopes and prospects for Cubesat-based space interferometry.
    • The HOSTS survey for exo-zodiacal dust: preliminary results and future prospects

      Ertel, Steve; Hinz, Phil; Defrère, Denis; Mennesson, Bertrand; Kennedy, Grant; Weinberger, Alycia J.; Phillip, Willems A.; Absil, Olivier; Arbo, Paul; Bailey, Vanessa P.; et al. (SPIE-INT SOC OPTICAL ENGINEERING, 2018-07-24)
      The presence of large amounts of dust in the habitable zones of nearby stars is a significant obstacle for future exo-Earth imaging missions. We executed the HOSTS (Hunt for Observable Signatures of Terrestrial Systems) survey to determine the typical amount of such exozodiacal dust around a sample of nearby main sequence stars. The majority of the data have been analyzed and we present here an update of our ongoing work. Nulling interferometry in N band was used to suppress the bright stellar light and to detect faint, extended circumstellar dust emission. We present an overview of the latest results from our ongoing work. We find seven new N band excesses in addition to the high confidence confirmation of three that were previously known. We find the first detections around Sun-like stars and around stars without previously known circumstellar dust. Our overall detection rate is 23%. The inferred occurrence rate is comparable for early type and Sun-like stars, but decreases from 71(-20)(+11) % for stars with previously detected mid- to far-infrared excess to 11(-4)(+9) % for stars without such excess, confirming earlier results at high confidence. For completed observations on individual stars, our sensitivity is five to ten times better than previous results. Assuming a lognormal luminosity function of the dust, we find upper limits on the median dust level around all stars without previously known mid to far infrared excess of 11.5 zodis at 95% confidence level. The corresponding upper limit for Sun-like stars is 16 zodis. An LBTI vetted target list of Sun-like stars for exo-Earth imaging would have a corresponding limit of 7.5 zodis. We provide important new insights into the occurrence rate and typical levels of habitable zone dust around main sequence stars. Exploiting the full range of capabilities of the LBTI provides a critical opportunity for the detailed characterization of a sample of exozodiacal dust disks to understand the origin, distribution, and properties of the dust.
    • Hybrid QKD Protocol Outperforming Both DV- and CV-QKD Protocols

      Djordjevic, Ivan B.; Univ Arizona, Dept Elect & Comp Engn (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2020-02)
      To overcome the limitations of both discrete variable (DV) and continuous variable (CV) QKD protocols, in this paper, a hybrid QKD protocol is proposed. In the proposed hybrid QKD protocol, Alice simultaneously performs discrete modulation (DM)-based encoding for CV-QKD subsystem and time-phase encoding for DV-QKD on a transmitter side and transmits such hybrid encoded pulse with optimized average number of photons per pulse. On receiver side, Bob employs a 1:2 optical space switch to select either DV-QKD receiver or CV-QKD receiver with the optimized probability of selection. Other compatible CV-QKD and DV-QKD protocols can also be used in hybrid QKD. Bob further performs the classical postprocessing applied to both subsystems so that resulting joint secure key is derived from both subsystems. The proposed hybrid QKD protocol significantly outperforms previously introduced both Gaussian modulation (GM)- and DM-based CV-QKD protocols as well as DV-QKD protocols in terms of both secret-key rate and achievable transmission distance.
    • Spatially Resolved [C ii] Emission in SPT0346-52: A Hyper-starburst Galaxy Merger at z ∼ 5.7

      Litke, Katrina C.; Marrone, Daniel P.; Spilker, Justin S.; Aravena, Manuel; Béthermin, Matthieu; Chapman, Scott; Chen, Chian-Chou; Breuck, Carlos de; Dong, Chenxing; Gonzalez, Anthony; et al. (IOP PUBLISHING LTD, 2019-01-10)
      SPT0346-52 is one of the most most luminous and intensely star-forming galaxies in the universe, with L-FIR > 10(13) L-circle dot and Sigma(SFR) approximate to 4200 M-circle dot yr(-1) kpc(-2). In this paper, we present similar to 0 ''(center dot)15 ALMA observations of the [C II] 158 mu m emission line in this z = 5.7 dusty star-forming galaxy. We use a pixellated lensing reconstruction code to spatially and kinematically resolve the source-plane [C II] and rest-frame 158 mu m dust continuum structure at similar to 700 pc (similar to 0 ''(center dot)12) resolution. We discuss the [C II] deficit with a pixellated study of the L-[C II]/L-FIR ratio in the source plane. We find that individual pixels within the galaxy follow the same trend found using unresolved observations of other galaxies, indicating that the deficit arises on scales less than or similar to 700 pc. The lensing reconstruction reveals two spatially and kinematically separated components (similar to 1 kpc and similar to 500 km s(-1) apart) connected by a bridge of gas. Both components are found to be globally unstable, with Toomre Q instability parameters << 1 everywhere. We argue that SPT0346-52 is undergoing a major merger, which is likely driving the intense and compact star formation.