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Featured submissions

September 2020

August 2020

July 2020

  • The UA Campus Repository team is thrilled about the launch of our sister repository, ReDATA. To deposit research datasets and code, please use the newly created UA Research Data Repository (ReDATA). ReDATA will curate the data and provide a DOI upon publication. Access is currently by request only. To obtain access, please contact data-management@arizona.edu.
  • The Discovery of a Gravitationally Lensed Quasar at z=6.51

    Fan, Xiaohui; Wang, Feige; Yang, Jinyi; Keeton, Charles R.; Yue, Minghao; Zabludoff, Ann; Bian, Fuyan; Bonaglia, Marco; Georgiev, Iskren Y.; Hennawi, Joseph F.; et al. (IOP PUBLISHING LTD, 2019-01-09)
    Strong gravitational lensing provides a powerful probe of the physical properties of quasars and their host galaxies. A high fraction of the most luminous high-redshift quasars was predicted to be lensed due to magnification bias. However, no multiple imaged quasar was found at z > 5 in previous surveys. We report the discovery of J043947.08+163415.7, a strongly lensed quasar at z = 6.51, the first such object detected at the epoch of reionization, and the brightest quasar yet known at z > 5. High-resolution Hubble Space Telescope imaging reveals a multiple imaged system with a maximum image separation theta similar to 0 ''.2, best explained by a model of three quasar images lensed by a low-luminosity galaxy at z similar to 0.7, with a magnification factor of similar to 50. The existence of this source suggests that a significant population of strongly lensed, high-redshift quasars could have been missed by previous surveys, as standard color selection techniques would fail when the quasar color is contaminated by the lensing galaxy.
  • Understanding the atmospheric properties and chemical composition of the ultra-hot Jupiter HAT-P-7b II. Mapping the effects of gas kinetics

    Molaverdikhani, K.; Helling, Ch.; Lew, B. W. P.; MacDonald, R. J.; Samra, D.; Iro, N.; Woitke, P.; Parmentier, V.; Univ Arizona, Lunar & Planetary Lab (EDP SCIENCES S A, 2020-03-03)
    Aims. The atmospheres of ultra-hot Jupiters (UHJs) are commonly considered to be at thermochemical equilibrium. We aim to provide disequilibrium chemistry maps for a global understanding of the chemistry in the atmosphere of HAT-P-7b and assess the importance of disequilibrium chemistry on UHJs. Methods. We applied a hierarchical modeling approach using 97 1D atmospheric profiles from a 3D general circulation model of HAT-P-7b. For each atmospheric 1D profile, we evaluated our kinetic cloud formation model consistently with the local gas-phase composition in chemical equilibrium. This served as input to study the quenching of dominating CHNO-binding molecules. We evaluated quenching results from a zeroth-order approximation in comparison to a kinetic gas-phase approach. Results. We find that the zeroth-order approach of estimating quenching points agrees well with the full gas-kinetic modeling results. However, it underestimates the quenching levels by about one order of magnitude at high temperatures. Chemical disequilibrium has the greatest effect on the nightside and morning abundance of species such as H, H2O, CH4, CO2, HCN, and all CnHm molecules; heavier CnHm molecules are more affected by disequilibrium processes. The CO abundance, however, is affected only marginally. While dayside abundances also notably change, those around the evening terminator of HAT-P-7b are the least affected by disequilibrium processes. The latter finding may partially explain the consistency of observed transmission spectra of UHJs with atmospheres in thermochemical equilibrium. Photochemistry only negligibly affects molecular abundances and quenching levels. Conclusions. In general, the quenching points of the atmosphere of HAT-P-7b are at much lower pressures than in the cooler hot-jupiters. We propose several avenues to determining the effect of disequilibrium processes on UHJs that are in general based on abundance and opacity measurements at different local times. It remains a challenge to completely disentangle this from the chemical effects of clouds and that of a primordial nonsolar abundance.
  • Stellar spectroscopy in the near-infrared with a laser frequency comb

    Metcalf, Andrew J.; Anderson, Tyler; Bender, Chad F.; Blakeslee, Scott; Brand, Wesley; Carlson, David R.; Cochran, William D.; Diddams, Scott A.; Endl, Michael; Fredrick, Connor; et al. (OPTICAL SOC AMER, 2019-02-20)
    The discovery and characterization of exoplanets around nearby stars are driven by profound scientific questions about the uniqueness of Earth and our solar system, and the conditions under which life could exist elsewhere in our galaxy. Doppler spectroscopy, or the radial velocity (RV) technique, has been used extensively to identify hundreds of exoplanets, but with notable challenges in detecting terrestrial mass planets orbiting within habitable zones. We describe infrared RV spectroscopy at the 10 m Hobby-Eberly Telescope that leverages a 30 GHz electro-optic laser frequency comb with a nanophotonic supercontinuum to calibrate the Habitable Zone Planet Finder spectrograph. Demonstrated instrument precision <10 cm/s and stellar RVs approaching 1 m/s open the path to discovery and confirmation of habitable-zone planets around M-dwarfs, the most ubiquitous type of stars in our galaxy. (c) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
  • Mass Calibration of Optically Selected DES Clusters Using a Measurement of CMB-cluster Lensing with SPTpol Data

    Raghunathan, S.; Patil, S.; Baxter, E.; Benson, B. A.; Bleem, L. E.; Chou, T. L.; Crawford, T. M.; Holder, G. P.; McClintock, T.; Reichardt, C. L.; et al. (IOP PUBLISHING LTD, 2019-02-20)
    We use cosmic microwave background (CMB) temperature maps from the 500 deg(2) SPTpol survey to measure the stacked lensing convergence of galaxy clusters from the Dark Energy Survey (DES) Year-3 redMaPPer (RM) cluster catalog. The lensing signal is extracted through a modified quadratic estimator designed to be unbiased by the thermal Sunyaev-Zel'dovich (tSZ) effect. The modified estimator uses a tSZ-free map, constructed from the SPTpol 95 and 150 GHz data sets, to estimate the background CMB gradient. For lensing reconstruction, we employ two versions of the RM catalog: a flux-limited sample containing 4003 clusters and a volume-limited sample with 1741 clusters. We detect lensing at a significance of 8.7 sigma(6.7 sigma) with the flux (volume)-limited sample. By modeling the reconstructed convergence using the Navarro-Frenk-White profile, we find the average lensing masses to be M-200 m =(1.62(-0.25)(+0.35) [stat.] +/- 0.04 [sys.] and (1.28(-0.18)(+0.14) [stat.] +/- 0.03 [sys.] x 10(14) M-circle dot for the volume- and flux-limited samples, respectively. The systematic error budget is much smaller than the statistical uncertainty and is dominated by the uncertainties in the RM cluster centroids. We use the volume-limited sample to calibrate the normalization of the mass-richness scaling relation, and find a result consistent with the galaxy weak-lensing measurements from DES.
  • OSSOS XI. No active centaurs in the Outer Solar System Origins Survey

    Cabral, Nahuel; Guilbert-Lepoutre, Aurélie; Fraser, Wesley C.; Marsset, Michaël; Volk, Kathryn; Petit, Jean-Marc; Rousselot, Philippe; Alexandersen, Mike; Bannister, Michele T.; Chen, Ying-Tung; et al. (EDP SCIENCES S A, 2019-01-15)
    Context. Centaurs are icy objects in transition between the trans-Neptunian region and the inner solar system, orbiting the Sun in the giant planet region. Some centaurs display cometary activity, which cannot be sustained by the sublimation of water ice in this part of the solar system, and has been hypothesized to be due to the crystallization of amorphous water ice. Aims. In this work, we investigate centaurs discovered by the Outer Solar System Origins Survey (OSSOS) and search for cometary activity. Tentative detections would improve understanding of the origins of activity among these objects. Methods. We search for comae and structures by fitting and subtracting both point spread functions and trailed point-spread functions from the OSSOS images of each centaur. When available, Col-OSSOS images were used to search also for comae. Results. No cometary activity is detected in the OSSOS sample. We track the recent orbital evolution of each new centaur to confirm that none would actually be predicted to be active, and we provide size estimates for the objects. Conclusions. The addition of 20 OSSOS objects to the population of similar to 250 known centaurs is consistent with the currently understood scenario, in which drastic drops in perihelion distance induce changes in the thermal balance prone to trigger cometary activity in the giant planet region.

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