Now showing items 12892-12911 of 12955

    • X Marks the Spot: Nexus of Filaments, Cores, and Outflows in a Young Star-forming Region

      Imara, Nia; Lada, Charles; Lewis, John; Bieging, John H.; Kong, Shuo; Lombardi, Marco; Alves, Joao; Univ Arizona, Steward Observ (IOP PUBLISHING LTD, 2017-05-15)
      We present a multiwavelength investigation of a region of a nearby giant molecular cloud that is distinguished by a minimal level of star formation activity. With our new (CO)-C-12(J = 2-1) and (CO)-C-13(J = 2-1) observations of a remote region within the middle of the California molecular cloud, we aim to investigate the relationship between filaments, cores, and a molecular outflow in a relatively pristine environment. An extinction map of the region from Herschel Space Observatory observations reveals the presence of two 2 pc long filaments radiating from a highextinction clump. Using the (CO)-C-13 observations, we show that the filaments have coherent velocity gradients and that their mass-per-unit-lengths may exceed the critical value above which filaments are gravitationally unstable. The region exhibits structure with eight cores, at least one of which is a starless, prestellar core. We identify a low-velocity, low-mass molecular outflow that may be driven by a flat spectrum protostar. The outflow does not appear to be responsible for driving the turbulence in the core with which it is associated, nor does it provide significant support against gravitational collapse.
    • The X-Ray and Mid-infrared Luminosities in Luminous Type 1 Quasars

      Chen(陳建廷), Chien-Ting J.; Hickox, Ryan C.; Goulding, Andrew D.; Stern, Daniel; Assef, Roberto; Kochanek, C. S.; Brown, Michael J. I.; Harrison, Chris M.; Hainline, Kevin N.; Alberts, Stacey; et al. (IOP PUBLISHING LTD, 2017-03-13)
      Several recent studies have reported different intrinsic correlations between the active galactic nucleus (AGN) mid-IR luminosity (L-MIR) and the rest-frame 2-10 keV luminosity (L-X) for luminous quasars. To understand the origin of the difference in the observed L-X-L-MIR relations, we study a sample of 3247 spectroscopically confirmed type 1 AGNs collected from Bootes, XMM-COSMOS, XMM-XXL-North, and the Sloan Digital Sky Survey quasars in the Swift/XRT footprint spanning over four orders of magnitude in luminosity. We carefully examine how different observational constraints impact the observed L-X-L-MIR relations, including the inclusion of X-ray-nondetected objects, possible X-ray absorption in type 1 AGNs, X-ray flux limits, and star formation contamination. We find that the primary factor driving the different L-X-L-MIR relations reported in the literature is the X-ray flux limits for different studies. When taking these effects into account, we find that the X-ray luminosity and mid-IR luminosity (measured at rest-frame 6 mu m, or L-6 mu m) of our sample of type 1 AGNs follow a bilinear relation in the log-log plane: log L-X = (0.84 +/- 0.03) logL(6) (mu m) /10(45)erg s(-1) + (44.60. +/- 0.01) for L-6 (mu m) < 10(44.79) erg s(-1), and log L-X (0.40 +/- 0.03) log L-6 (mu m)/10(45) erg s(-1) + (44.51 +/- 0.01) for L-6 mu m. 1044.79 erg s(-1). This suggests that the luminous type 1 quasars have a shallower LX-L6mmcorrelation than the approximately linear relations found in local Seyfert galaxies. This result is consistent with previous studies reporting a luminosity-dependent LX-LMIRrelation and implies that assuming a linear LX-L-6 mu m relation to infer the neutral gas column density for X-ray absorption might overestimate the column densities in luminous quasars.
    • X-ray constraints on the fraction of obscured active galactic nuclei at high accretion luminosities

      Georgakakis, A.; Salvato, M.; Liu, Z.; Buchner, J.; Brandt, W. N.; Ananna, T. Tasnim; Schulze, A.; Shen, Yue; LaMassa, S.; Nandra, K.; et al. (OXFORD UNIV PRESS, 2017-08)
      The wide-area XMM-XXL X-ray survey is used to explore the fraction of obscured active galactic nuclei (AGNs) at high accretion luminosities, L-X(2-10 keV) greater than or similar to 10(44) erg s(-1), and out to redshift z approximate to 1.5. The sample covers an area of about 14 deg(2) and provides constraints on the space density of powerful AGNs over a wide range of neutral hydrogen column densities extending beyond the Compton-thick limit, N-H approximate to 10(24) cm(-2). The fraction of obscured Compton-thin (N-H = 10(22) - 10(24) cm(-2)) AGNs is estimated to be approximate to 0.35 for luminosities L-X(2-10 keV) > 10(44) erg s(-1), independent of redshift. For less luminous sources, the fraction of obscured Compton-thin AGNs increases from 0.45 +/- 0.10 at z = 0.25 to 0.75 +/- 0.05 at z = 1.25. Studies that select AGNs in the infrared via template fits to the observed spectral energy distribution of extragalactic sources estimate space densities at high accretion luminosities consistent with the XMM-XXL constraints. There is no evidence for a large population of AGNs (e.g. heavily obscured) identified in the infrared and missed at X-ray wavelengths. We further explore the mid-infrared colours of XMM-XXL AGNs as a function of accretion luminosity, column density and redshift. The fraction of XMM-XXL sources that lie within the mid-infrared colour wedges defined in the literature to select AGNs is primarily a function of redshift. This fraction increases from about 20-30 per cent at z = 0.25 to about 50-70 per cent at z = 1.5.
    • X-ray Lightcurves from Realistic Polar Cap Models: Inclined Pulsar Magnetospheres and Multipole Fields

      Lockhart, Will; Gralla, Samuel E; Özel, Feryal; Psaltis, Dimitrios; Univ Arizona, Dept Phys; Univ Arizona, Dept Astron; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2019-09-09)
      Thermal X-ray emission from rotation-powered pulsars is believed to originate from localized ‘hotspots’ on the stellar surface occurring where large-scale currents from the magnetosphere return to heat the atmosphere. Light-curve modelling has primarily been limited to simple models, such as circular antipodal emitting regions with constant temperature. We calculate more realistic temperature distributions within the polar caps, taking advantage of recent advances in magnetospheric theory, and we consider their effect on the predicted light curves. The emitting regions are non-circular even for a pure dipole magnetic field, and the inclusion of an aligned magnetic quadrupole moment introduces a north–south asymmetry. As the quadrupole moment is increased, one hotspot grows in size before becoming a thin ring surrounding the star. For the pure dipole case, moving to the more realistic model changes the light curves by 5−10percent for millisecond pulsars, helping to quantify the systematic uncertainty present in current dipolar models. Including the quadrupole gives considerable freedom in generating more complex light curves. We explore whether these simple dipole+quadrupole models can account for the qualitative features of the light curve of PSR J0437−4715.
    • X-ray measurement model and information-theoretic metric incorporating material variability with spatial and energy correlations

      Ding, Yijun; Ashok, Amit; Univ Arizona, James C Wyant Coll Opt Sci; Univ Arizona, Dept Elect & Comp Engn (SPIE-INT SOC OPTICAL ENGINEERING, 2020-06-01)
      Extending our prior work, we propose an X-ray measurement model that incorporates spatial-correlated material variability. The model enables more accurate task-specific assessment of the performance of X-ray imaging and sensing systems. More specifically, the model can be used to calculate bounds on the probability of error (P-e) for threat-detection tasks. We analyze the performance of a prototypical X-ray measurement system to compare the new spatial- and energy-correlated model with the previous model, which ignores the spatial correlation.
    • X-Ray Measurements of the Particle Acceleration Properties at Inward Shocks in Cassiopeia A

      Sato, Toshiki; Katsuda, Satoru; Morii, Mikio; Bamba, Aya; Hughes, John P.; Maeda, Yoshitomo; Ishida, Manabu; Fraschetti, Federico; Univ Arizona, Dept Planetary Sci & Astron (IOP PUBLISHING LTD, 2018-01-22)
      We present new evidence that the bright nonthermal X-ray emission features in the interior of the Cassiopeia A supernova remnant are caused by inward-moving shocks, based on Chandra and NuSTAR observations. Several bright inward-moving filaments were identified using monitoring data taken by Chandra in 2000-2014. These inward-moving shock locations are nearly coincident with hard X-ray (15-40 keV) hot spots seen by NuSTAR. From proper-motion measurements, the transverse velocities were estimated to be in the range of similar to 2100-3800 km s(-1) for a distance of 3.4 kpc. The shock velocities in the frame of the expanding ejecta reach values of similar to 5100-8700 km s(-1), which is slightly higher than the typical speed of the forward shock. Additionally, we find flux variations (both increasing and decreasing) on timescales of a few years in some of the inward-moving shock filaments. The rapid variability timescales are consistent with an amplified magnetic field of B similar to 0.5-1 mG. The high speed and low photon cut-off energy of the inward-moving shocks are shown to imply a particle diffusion coefficient that departs from the Bohm regime (k(0) = D-0/D-0,D-Bohm similar to 3-8) for the few simple physical configurations we consider in this study. The maximum electron energy at these shocks is estimated to be similar to 8-11 TeV, which is smaller than the values of similar to 15-34 TeV that were inferred for the forward shock. Cassiopeia A is dynamically too young for its reverse shock to appear to be moving inward in the observer frame. We propose instead that the inward-moving shocks are a consequence of the forward shock encountering a density jump of 5-8 in the surrounding material.
    • X-Ray Observations of a [CII]-bright, z=6.59 Quasar/Companion System

      Connor, Thomas; Banados, Eduardo; Mazzucchelli, Chiara; Stern, Daniel; Decarli, Roberto; Fan, Xiaohui; Farina, Emanuele Paolo; Lusso, Elisabeta; Neeleman, Marcel; Walter, Fabian; et al. (IOP PUBLISHING LTD, 2020-09)
      We present deep Chandra observations of PSO J231.6576-20.8335, a quasar at redshift z = 6.59 with a nearby (similar to 8 proper kpc) companion galaxy. The Atacama Large Millimeter/submillimeter Array observed both the quasar and companion to be bright in [CII], and the system has significant extended Ly alpha emission around the quasar, suggesting that a galaxy merger is ongoing. Unlike previous studies of two similar systems, and despite observing the system with Chandra for 140 ks, we do not detect the companion in X-rays. The quasar itself is detected, but only 13.3(-3.7)(+4.8) net counts are observed. From a basic spectral analysis, the X-ray spectrum of the quasar is soft (hardness ratio of HR = -0.60(-0.27)(+0.17), power-law index of Gamma = 2.6(-0.9)(+1.0)), which results in a rest-frame X-ray luminosity comparable to other bright quasars L-2.10 = 1.09(-.070)(+2.20) x 10(45) ers s(-1)) despite the faint observed X-ray flux. We highlight two possible interpretations of this result: the quasar has a steep value of Gamma-potentially related to observed ongoing Eddington accretion-thereby pushing much of the emission out of our observed band, or the quasar has a more normal spectrum (Gamma similar to 2) but is therefore less X-ray luminous (L2-10 similar to 0.6 x 1(04) erg s(-1)).
    • X-Ray Observations of a z ∼ 6.2 Quasar/Galaxy Merger

      Connor, Thomas; Bañados, Eduardo; Stern, Daniel; Decarli, Roberto; Schindler, Jan-Torge; Fan, Xiaohui; Farina, Emanuele Paolo; Mazzucchelli, Chiara; Mulchaey, John S.; Walter, Fabian; et al. (IOP PUBLISHING LTD, 2019-12-18)
      Quasars at early redshifts (z > 6) with companion galaxies offer unique insights into the growth and evolution of the first supermassive black holes. Here, we report on a 150 ks Chandra observation of PSO.J308.0416-21.2339, a z = 6.23 quasar with a merging companion galaxy identified in [C II] and rest-frame UV emission. With 72.3(-8.6)(+9.6) net counts, we find that PSO.J308.0416-21.2339 is powerful (L-X = 2.31(-0.76)(+1.14) x 10(45) erg s(-1) cm(-2) in rest-frame 2.0-10.0 keV) yet soft (spectral power-law index Gamma = 2.39(-0.36)(+0.37) and optical-to-X-ray slope alpha(OX) = -1.41 +/- 0.11). In addition, we detect three hard-energy photons 2 ''.0 to the west of the main quasar, cospatial with the brightest UV emission of the merging companion. As no soft-energy photons are detected in the same area, this is potentially indicative of a highly obscured source. With conservative assumptions, and accounting for both background fluctuations and the extended wings of the quasar's emission, these photons only have a probability P = 0.021 of happening by chance. If confirmed by deeper observations, this system is the first high-redshift quasar and companion individually detected in X-rays and is likely a dual active galactic nucleus.
    • X-ray scaling relations from a complete sample of the richest maxBCG clusters

      Ge, Chong; Sun, Ming; Rozo, Eduardo; Sehgal, Neelima; Vikhlinin, Alexey; Forman, William; Jones, Christine; Nagai, Daisuke; Univ Arizona, Dept Phys (OXFORD UNIV PRESS, 2019-04)
      We use a complete sample of 38 richest maxBCG clusters to study the ICM-galaxy scaling relations and the halo mass selection properties of the maxBCG algorithm, based on X-ray and optical observations. The clusters are selected from the two largest bins of optical richness in the Planck stacking work with the maxBCG richness N-200 >= 78. We analyse their Chandra and XMM Newton data to derive the X-ray properties of the ICM. We then use the distribution of P(X vertical bar N), X = T-X, L-X, Y-X, to study the mass selection P(M vertical bar N) of maxBCG. Compared with previous works based on the whole richness sample, a significant fraction of blended systems with boosted richness is skewed into this richest sample. Parts of the blended haloes are picked apart by the redMaPPer, an updated red-sequence cluster finding algorithm with lower mass scatter. Moreover, all the optical blended haloes are resolved as individual X-ray haloes, following the established L-X-T-X and L-X-Y-X relations. We further discuss that the discrepancy between ICM-galaxy scaling relations, especially for future blind stacking, can come from several factors, including miscentring, projection, contamination of low-mass systems, mass bias, and covariance bias. We also evaluate the fractions of relaxed and cool core clusters in our sample. Both are smaller than those from SZ or X-ray selected samples. Moreover, disturbed clusters show a higher level of mass bias than relaxed clusters.
    • X-ray study of the double source plane gravitational lens system Eye of Horus observed with XMM-Newton

      Tanaka, Keigo; Tsuji, Ayumi; Akamatsu, Hiroki; Chan, J H H; Coupon, Jean; Egami, Eiichi; Finet, Francois; Fujimoto, Ryuichi; Ichinohe, Yuto; Jaelani, Anton T; et al. (OXFORD UNIV PRESS, 2019-11-15)
      A double source plane (DSP) system is a precious probe for the density profile of distant galaxies and cosmological parameters. However, these measurements could be affected by the surrounding environment of the lens galaxy. Thus, it is important to evaluate the cluster-scale mass for detailed mass modelling. We observed the Eye of Horus, a DSP system discovered by the Hyper Suprime-Cam Subaru Strategic Survey (HSC-SSP), with XMM-Newton. We detected two X-ray extended emissions, originating from two clusters, one centred at the Eye of Horus, and the other located similar to 100 arcsec north-east to the Eye of Horus. We determined the dynamical mass assuming hydrostatic equilibrium, and evaluated their contributions to the lens mass interior of the Einstein radius. The contribution of the former cluster is 1.1(-0.5)(+1.2) x 10(12) M-circle dot, which is 21-76 per cent of the total mass within the Einstein radius. The discrepancy is likely due to the complex gravitational structure along the line of sight. On the other hand, the contribution of the latter cluster is only similar to 2 per cent on the Eye of Horus. Therefore, the influence associated with this cluster can be ignored.
    • X-Rays from the Redshift 7.54 Quasar ULAS J1342+0928

      Bañados, Eduardo; Connor, Thomas; Stern, Daniel; Mulchaey, John; Fan, Xiaohui; Decarli, R.; Farina, Emanuele P.; Mazzucchelli, C.; Venemans, B. P.; Walter, Fabian; et al. (IOP PUBLISHING LTD, 2018-03-27)
      We present a 45 ks Chandra observation of the quasar ULAS J1342+0928 at z=7.54. We detect 14.0(-3.7)(+4.8) counts from the quasar in the observed-frame energy range 0.5-7.0 keV (6 sigma detection), representing the most distant non-transient astronomical source identified in X-rays to date. The present data are sufficient only to infer rough constraints on the spectral parameters. We find an X-ray hardness ratio of HR = -0.51(-0.28)(+0.26) between the 0.5-2.0 keV and 2.0-7.0 keV ranges and derive a power-law photon index of Gamma= 1.95(-0.53)(+0.55). Assuming a typical value for high-redshift quasars of Gamma = 1.9, ULAS J1342+0928 has a 2-10 keV rest-frame X-ray luminosity of L2-10 = 11.6(-3.5)(+4.3) x 10(44) erg s(-1). Its X-ray-to-optical power-law slope is alpha(OX) = -1.67(-0.10)(+0.16), consistent with the general trend indicating that the X-ray emission in the most bolometrically powerful quasars is weaker relative to their optical emission.
    • X-shooter study of accretion in Chamaeleon I

      Manara, C. F.; Testi, L.; Herczeg, G. J.; Pascucci, I.; Alcalá, J. M.; Natta, A.; Antoniucci, S.; Fedele, D.; Mulders, G. D.; Henning, T.; et al. (EDP SCIENCES S A, 2017-08-25)
      The dependence of the mass accretion rate on the stellar properties is a key constraint for star formation and disk evolution studies. Here we present a study of a sample of stars in the Chamaeleon I star-forming region carried out using spectra taken with the ESO VLT/X-shooter spectrograph. The sample is nearly complete down to stellar masses (M-star) similar to 0.1 M-circle dot for the young stars still harboring a disk in this region. We derive the stellar and accretion parameters using a self-consistent method to fit the broadband flux-calibrated medium resolution spectrum. The correlation between accretion luminosity to stellar luminosity, and of mass accretion rate to stellar mass in the logarithmic plane yields slopes of 1.9 +/- 0.1 and 2.3 +/- 0.3, respectively. These slopes and the accretion rates are consistent with previous results in various star-forming regions and with different theoretical frameworks. However, we find that a broken power-law fit, with a steeper slope for stellar luminosity lower than similar to 0.45 L-circle dot and for stellar masses lower than similar to 0.3 M-circle dot is slightly preferred according to different statistical tests, but the single power-law model is not excluded. The steeper relation for lower mass stars can be interpreted as a faster evolution in the past for accretion in disks around these objects, or as different accretion regimes in different stellar mass ranges. Finally, we find two regions on the mass accretion versus stellar mass plane that are empty of objects: one region at high mass accretion rates and low stellar masses, which is related to the steeper dependence of the two parameters we derived. The second region is located just above the observational limits imposed by chromospheric emission, at M-star similar to 0.3-0.4 M-circle dot. These are typical masses where photoevaporation is known to be effective. The mass accretion rates of this region are similar to 10(-10) M-circle dot/yr, which is compatible with the value expected for photoevaporation to rapidly dissipate the inner disk.
    • X-shooter survey of disk accretion in Upper Scorpius

      Manara, C. F.; Natta, A.; Rosotti, G. P.; Alcalá, J. M.; Nisini, B.; Lodato, G.; Testi, L.; Pascucci, I.; Hillenbrand, L.; Carpenter, J.; et al. (EDP SCIENCES S A, 2020-07-07)
      Determining the mechanisms that drive the evolution of protoplanetary disks is a necessary step toward understanding how planets form. For this work, we measured the mass accretion rate for young stellar objects with disks at age > 5 Myr, a critical test for the current models of disk evolution. We present the analysis of the spectra of 36 targets in the similar to 5-10 Myr old Upper Scorpius star-forming region for which disk masses were measured with ALMA. We find that the mass accretion rates in this sample of old but still surviving disks are similarly high as those of the younger (similar to 1-3 Myr old) star-forming regions of Lupus and Chamaeleon I, when considering the dependence on stellar and disk mass. In particular, several disks show high mass accretion rates greater than or similar to 10(-9) M-circle dot yr(-1) while having low disk masses. Furthermore, the median values of the measured mass accretion rates in the disk mass ranges where our sample is complete at a level similar to 60-80% are compatible in these three regions. At the same time, the spread of mass accretion rates at any given disk mass is still > 0.9 dex, even at age > 5 Myr. These results are in contrast with simple models of viscous evolution, which would predict that the values of the mass accretion rate diminish with time, and a tighter correlation with disk mass at age > 5 Myr. Similarly, simple models of internal photoevaporation cannot reproduce the observed mass accretion rates, while external photoevaporation might explain the low disk masses and high accretion rates. A possible partial solution to the discrepancy with the viscous models is that the gas-to-dust ratio of the disks at similar to 5-10 Myr is significantly different and higher than the canonical 100, as suggested by some dust and gas disk evolution models. The results shown here require the presence of several interplaying processes, such as detailed dust evolution, external photoevaporation, and possibly MHD winds, to explain the secular evolution of protoplanetary disks.
    • Xm(2) Scores for Estimating Total Exposure to Multimodal Strategies Identified by Pharmacists for Managing Pain: Validity Testing and Clinical Relevance

      Axon, David Rhys; Bhattacharjee, Sandipan; Warholak, Terri L; Slack, Marion K; Univ Arizona, Coll Pharm, Dept Pharm Practice & Sci (HINDAWI LTD, 2018-01-01)
      Objective. To assess the validity of an exposure score obtained from the Xm(2) tool for all pharmacological and nonpharmacological strategies used by individuals to manage chronic pain. Methods. Using data from individuals with chronic pain, eXposure multimodal (Xm(2)) scores were calculated by assigning one point for every 100 mg of morphine equivalent used (opioid medications); 25% of the maximum recommended exposure used (nonopioid medications); and any use of another strategy then summed. Content, criterion, construct, and convergent validity were assessed. Results. The sample of 149 individuals used a mean of 12.6 (SD = 4.6) strategies to manage pain and had a mean Xm(2) score of 16.8 (SD = 9.1). Content validity was established by demonstrating that the pain management strategies identified were also reported in the literature. Criterion validity was established by the positive association of exposure scores with the following: interference with work (odds ratio (OR) = 2.23, 95% confidence interval (CI) = 1.14-4.36), daily activities (OR = 2.10, CI = 1.07-4.13), relationships (OR = 1.98, CI = 1.01-3.88), and leisure activities (OR = 2.31, CI = 1.18-4.50); workdays missed (OR = 5.10, CI = 1.92-13.58); emergency department visits (OR = 3.40, CI = 1.17-9.91); hospitalizations (OR = 4.18, CI = 0.86-20.37); and by a negative association with satisfaction (OR = 0.40, CI = 0.18-0.88). Construct validity was established by the positive association of exposure with baseline pain intensity (p < 0.01) and odds of experiencing an adverse event (OR = 2.31, CI = 1.18-4.52). Convergent validity was established through correlations of pain intensity from the Xm(2) score and existing quantitative analgesic questionnaire (QAQ) score. Discussion. Xm(2) scores represent a valid estimate of total exposure to multimodal strategies used and provide clinically relevant information for deciding what strategies to use at what level.
    • XMM–Newton observation of the ultraluminous quasar SDSS J010013.02+280225.8 at redshift 6.326

      Ai, Yanli; Fabian, A. C.; Fan, Xiaohui; Walker, S. A.; Ghisellini, G.; Sbarrato, T.; Dou, Liming; Wang, Feige; Wu, Xue-Bing; Feng, Longlong; et al. (OXFORD UNIV PRESS, 2017-09)
      A brief Chandra observation of the ultraluminous quasar SDSS J010013.02+280225.8 at redshift 6.326 showed it to be a relatively bright, soft X-ray source with a count rate of about 1 count ks(-1). In this article, we present results for the quasar from a 65-ks XMM-Newton observation, which constrains its spectral shape well. The quasar is clearly detected with a total of similar to 460 net counts in the 0.2-10 keV band. The spectrum is characterized by a simple power-law model with a photon index of Gamma = 2.30(-0.10)(+0.10) and the intrinsic 2-10 keV luminosity is 3.14 x 10(45) erg s(-1). The 1 sigma upper limit to any intrinsic absorption column density is N-H = 6.07 x 10(22) cm(-2). No significant iron emission lines were detected. We derive an X-ray-to- optical flux ratio alpha(ox) of -1.74 +/- 0.01, consistent with the values found in other quasars of comparable ultraviolet luminosity. We did not detect significant flux variations either in the XMM-Newton exposure or between XMM-Newton and Chandra observations, which are separated by similar to 8 months. The X-ray observation enables the bolometric luminosity to be calculated after modelling the spectral energy distribution: the accretion rate is found to be sub-Eddington.
    • XQ-100: A legacy survey of one hundred 3.5 ≲ z ≲ 4.5 quasars observed with VLT/X-shooter

      López, S.; D’Odorico, V.; Ellison, S. L.; Becker, G. D.; Christensen, L.; Cupani, G.; Denney, K. D.; Pâris, I.; Worseck, G.; Berg, T. A. M.; et al. (EDP SCIENCES S A, 2016-10-18)
      We describe the execution and data reduction of the European Southern Observatory Large Programme "Quasars and their absorption lines: a legacy survey of the high-redshift Universe with VLT/X-shooter" (hereafter "XQ-100"). XQ-100 has produced and made publicly available a homogeneous and high-quality sample of echelle spectra of 100 quasars (QSOs) at redshifts z similar or equal to 3.5-4.5 observed with full spectral coverage from 315 to 2500 nm at a resolving power ranging from R similar to 4000 to 7000, depending on wavelength. The median signal-to-noise ratios are 33, 25 and 43, as measured at rest-frame wavelengths 1700, 3000 and 3600 angstrom, respectively. This paper provides future users of XQ-100 data with the basic statistics of the survey, along with details of target selection, data acquisition and data reduction. The paper accompanies the public release of all data products, including 100 reduced spectra. XQ-100 is the largest spectroscopic survey to date of high-redshift QSOs with simultaneous rest-frame UV/optical coverage, and as such enables a wide range of extragalactic research, from cosmology and galaxy evolution to AGN astrophysics.
    • XR Accessibility Initiatives in Academic Libraries

      Lischer‐Katz, Zack; Clark, Jasmine; University of Arizona (Wiley, 2021-10-13)
      Virtual reality and other extended reality (XR) technologies are being integrated into academic libraries to support research and teaching in innovative ways; however, new technologies are often adopted without considering disabled users. XR accessibility depends on establishing appropriate policies and best practices. This paper examines the current state of XR accessibility initiatives in academic libraries by reporting findings from a survey sent to the academic library community from February to May 2021.
    • XUV Transient Absorption Spectroscopy: Probing Laser-Perturbed Dipole Polarization in Single Atom, Macroscopic, and Molecular Regimes

      Liao, Chen-Ting; Sandhu, Arvinder; Univ Arizona, Coll Opt Sci; Univ Arizona, Dept Phys (MDPI AG, 2017-03-08)
      We employ an extreme ultraviolet (XUV) pulse to impulsively excite dipole polarization in atoms or molecules, which corresponds to coherently prepared superposition of excited states. A delayed near infrared (NIR) pulse then perturbs the fast evolving polarization, and the resultant absorbance change is monitored in dilute helium, dense helium, and sulfur hexafluoride (SF6) molecules. We observe and quantify the time-dependence of various transient phenomena in helium atoms, including laser-induced phase (LIP), time-varying (AC) Stark shift, quantum path interference, and laser-induced continuum structure. In the case of dense helium targets, we discuss nonlinear macroscopic propagation effects pertaining to LIP and resonant pulse propagation, which account for the appearance of new spectral features in transient lineshapes. We then use tunable NIR photons to demonstrate the wavelength dependence of the transient laser induced effects. In the case of molecular polarization experiment in SF6, we show suppression of XUV photoabsorption corresponding to inter-valence transitions in the presence of a strong NIR field. In each case, the temporal evolution of transient absorption spectra allows us to observe and understand the transient laser induced modifications of the electronic structure of atoms and molecules.
    • The Yarlung suture mélange, Lopu Range, southern Tibet: Provenance of sandstone blocks and transition from oceanic subduction to continental collision

      Metcalf, Kathryn; Kapp, Paul; Department of Geosciences, University of Arizona, Tucson, AZ, USA (ELSEVIER SCIENCE BV, 2017-08)
      With the aim of better understanding the history of ocean closure and suturing between India and Asia, we conducted a geologic investigation of a siliciclastic matrix tectonic melange within the western Yarlung suture zone of southern Tibet (Lopu Range region, similar to 50 km northwest of Saga). The siliciclastic matrix melange includes abundant blocks of ocean plate stratigraphy and sparse blocks of sandstone. Metapelite and metabasite blocks in the melange exhibit lower greenschist fades mineral assemblages, indicating that they were not deeply subducted. We obtained detrital zircon U-Pb geochronologic and sandstone petrographic data from sandstone blocks in the melange and sandstone beds from Tethyan Himalayan strata exposed to the south of the suture. The sandstones from both units are all similar in U-Pb detrital zircon age spectra and petrography to the nearby Tethyan Cretaceous-Paleocene Sangdanlin section, which records the earliest appearance (at similar to 59 Ma) of arc-affinity strata deposited conformably on Indian-affinity strata. Two Paleocene sandstones, one of which is a schistose block incorporated in the siliciclastic matrix melange, yielded indistinguishable maximum depositional ages of similar to 59 Ma. Mesozoic Asian-affinity sandstone blocks previously documented in the siliciclastic matrix melange 200-500 km along strike to the east are notably absent in the Lopu Range region. We documented a gradational transition in structural style from the block-in-matrix melange in the northeast to the south-vergent Tethyan thrust belt in the southwest. Blocks of Tethyan Himalayan strata increase in size and the volumetric proportion of matrix decreases from northeast to southwest. We conclude that no arc-affinity sandstone blocks were incorporated into the subduction complex until India-Asia collision at similar to 59 Ma when the Xigaze forearc basin became overfilled and Tethyan Himalayan strata entered the trench. As collision progressed, there was a gradual transition in structural style from block-in-matrix melange formation to imbricate-style thrust belt formation. (C) 2017 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
    • Yaws resurgence in Bankim, Cameroon: The relative effectiveness of different means of detection in rural communities

      Boock, Alphonse Um; Awah, Paschal Kum; Mou, Ferdinand; Nichter, Mark; Univ Arizona, Sch Anthropol (PUBLIC LIBRARY SCIENCE, 2017-05-08)
      Background Yaws is an infectious, debilitating and disfiguring disease of poverty that mainly affects children in rural communities in tropical areas. In Cameroon, mass-treatment campaigns carried out in the 1950s reduced yaws to such low levels that it was presumed the disease was eradicated. In 2010, an epidemiological study in Bankim Health District detected 29 cases of yaws. Five different means of detecting yaws in clinical and community settings were initiated in Bankim over the following five years. Methodology This observational study reviews data on the number of cases of yaws identified by each of the five yaws detection approaches: 1) passive yaws detection at local clinics after staff attended Neglected Tropical Disease awareness workshops, 2) community-based case detection carried out in remote communities by hospital staff who relied on community health workers to identify cases, 3) yaws screening following mass Buruli Ulcer outreach programs being piloted in the district, 4) school-based screening programs conducted as stand-alone and follow-up activities to mass outreach events, and 5) house to house active surveillance activities conducted in thirty-eight communities. Implementation of each of the four community-based approaches was observed by a team of health social scientists tasked with assessing the strengths and limitations of each detection method. Findings Eight hundred and fifteen cases of yaws were detected between 2012 and 2015. Only 7% were detected at local clinics. Small outreach programs and household surveys detected yaws in a broad spectrum of communities. The most successful means of yaws detection, accounting for over 70% of cases identified, were mass outreach programs and school based screenings in communities where yaws was detected. Conclusion The five interventions for detecting yaws had a synergistic effect and proved to be valuable components of a yaws eradication program. Well planned, culturally sensitive mass out-reach educational programs accompanied by school-based programs proved to be particularly effective in Bankim. Including yaws detection in a Buruli Ulcer outreach program constituted a win-win situation, as the demonstration effect of yaws treatment (rapid cure) increased confidence in early Buruli ulcer treatment. Mass outreach programs functioned as magnets for both diseases as well as other kinds of chronic wounds that future outreach programs need to address.