Now showing items 1-20 of 7088

    • 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.
    • Mapping observations of complex organic molecules around Sagittarius B2 with the ARO 12 m telescope

      Li, Juan; Wang, Junzhi; Qiao, Haihua; Quan, Donghui; Fang, Min; Du, Fujun; Li, Fei; Shen, Zhiqiang; Li, Shanghuo; Li, Di; et al. (OXFORD UNIV PRESS, 2020-01-04)
      We have performed high-sensitivity mapping observations of several complex organic molecules around Sagittarius B2 with the ARO 12 m telescope at 3 mm wavelength. Based on their spatial distribution, molecules can be classified as either 'extended', those detected not only in Sgr B2(N) and Sgr B2(M), or 'compact', those only detected toward or near Sgr B2(N) and Sgr B2(M). The 'extended' molecules include glycolaldehyde (CH2OHCHO), methyl formate (CH3OCHO), formic acid (t-HCOOH), ethanol (C2H5OH) and methyl amine (CH3NH2), while the 'compact' molecules include dimethyl ether (CH3OCH3), ethyl cyanide (C2H5CN), and amino acetonitrile (H2NCH2CN). These 'compact' molecules are likely produced under strong UV radiation, while the 'extended' molecules are likely formed at low temperatures, via gas-phase or grain-surface reactions. The spatial distribution of 'warm' CH2OHCHO at 89 GHz differs from the spatial distribution of 'cold' CH2OHCHO observed at 13 GHz. We found evidence for an overabundance of CH2OHCHO compared to that expected from the gas-phase model, which indicates that grain-surface reactions are necessary to explain the origin of CH2OHCHO in Sagittarius B2. Grain-surface reactions are also needed to explain the correlation between the abundances of 'cold' CH2OHCHO and C2H5OH. These results demonstrate the importance of grain-surface chemistry in the production of complex organic molecules.
    • Homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code – II. The Southern clusters and overview

      Mészáros, Szabolcs; Masseron, Thomas; García-Hernández, D A; Allende Prieto, Carlos; Beers, Timothy C; Bizyaev, Dmitry; Chojnowski, Drew; Cohen, Roger E; Cunha, Katia; Dell’Agli, Flavia; et al. (OXFORD UNIV PRESS, 2019-12-16)
      We investigate the Fe, C, N, O, Mg, Al, Si, K, Ca, Ce, and Nd abundances of 2283 red giant stars in 31 globular clusters from high-resolution spectra observed in both the Northern and Southern hemisphere by the SDSS-IV APOGEE-2 survey. This unprecedented homogeneous data set, largest to date, allows us to discuss the intrinsic Fe spread, the shape, and statistics of Al-Mg and N-C anti-correlations as a function of cluster mass, luminosity, age, and metallicity for all 31 clusters. We find that the Fe spread does not depend on these parameters within our uncertainties including cluster metallicity, contradicting earlier observations. We do not confirm the metallicity variations previously observed in M22 and NGC 1851. Some clusters show a bimodal Al distribution, while others exhibit a continuous distribution as has been previously reported in the literature. We confirm more than two populations in omega Cen and NGC 6752, and find new ones in M79. We discuss the scatter of Al by implementing a correction to the standard chemical evolution of Al in the Milky Way. After correction, its dependence on cluster mass is increased suggesting that the extent of Al enrichment as a function of mass was suppressed before the correction. We observe a turnover in the Mg-Al anticorrelation at very low Mg in omega Cen, similar to the pattern previously reported in M15 and M92. omega Cen may also have a weak K-Mg anticorrelation, and if confirmed, it would be only the third cluster known to show such a pattern.
    • WASP-52b. The effect of starspot correction on atmospheric retrievals

      Bruno, Giovanni; Lewis, Nikole K; Alam, Munazza K; López-Morales, Mercedes; Barstow, Joanna K; Wakeford, Hannah R; Sing, David; Henry, Gregory W; Ballester, Gilda E; Bourrier, Vincent; et al. (OXFORD UNIV PRESS, 2019-11-18)
      We perform atmospheric retrievals on the full optical to infrared (0.3-5 mu m) transmission spectrum of the inflated hot Jupiter WASP-52b by combining HST/STIS, WFC3 IR, and Spitzer/IRAC observations. As WASP-52 is an active star that shows both out-of-transit photometric variability and star-spot crossings during transits, we account for the contribution of non-occulted active regions in the retrieval. We recover a 0.1-10x solar atmospheric composition, in agreement with core accretion predictions for giant planets, and no significant contribution of aerosols. We also obtain a <3000K temperature for the star-spots, a measure which is likely affected by the models used to fit instrumental effects in the transits, and a 5 per cent star-spot fractional coverage, compatible with expectations for the host star's spectral type. Such constraints on the planetary atmosphere and on the activity of its host star will inform future JWST GTO observations of this target.
    • 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.
    • Cosmology with Stacked Cluster Weak Lensing and Cluster-Galaxy Cross-Correlations

      Salcedo, Andrés N; Wibking, Benjamin D; Weinberg, David H; Wu, Hao-Yi; Ferrer, Douglas; Eisenstein, Daniel; Pinto, Philip; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2019-10-23)
      Cluster weak lensing is a sensitive probe of cosmology, particularly the amplitude of matter clustering sigma(8) and matter density parameter Omega(m). The main nuisance parameter in a cluster weak lensing cosmological analysis is the scatter between the true halo mass and the relevant cluster observable, denoted sigma(lnMc). We show that combining the cluster weak lensing observable Delta Sigma with the projected cluster-galaxy cross-correlation function w(p,cg) and galaxy autocorrelation function w(p,g)g can break the degeneracy between sigma(8) and s(lnMc) to achieve tight, per cent-level constraints on sigma(8). Using a grid of cosmological N-body simulations, we compute derivatives of Delta Sigma, w(p,cg), and w(p,gg) with respect to sigma(8), Omega(m), sigma(lnMc), and halo occupation distribution (HOD) parameters describing the galaxy population. We also compute covariance matrices motivated by the properties of the Dark Energy Survey cluster and weak lensing survey and the BOSS CMASS galaxy redshift survey. For our fiducial scenario combining Delta Sigma, w(p,cg), and w(p,gg) measured over 0.3-30.0 h(-1) Mpc, for clusters at z = 0.35-0.55 above a mass threshold M-c approximate to 2 x 10(14) h(-1) M-circle dot, we forecast a 1.4 per cent constraint on sigma(8) while marginalizing over sigma(lnMc) and all HOD parameters. Reducing the mass threshold to 1 x 10(14) h(-1) M-circle dot and adding a z = 0.15-0.35 redshift bin sharpens this constraint to 0.8 per cent. The small-scale (r(p) < 3.0 h(-1) Mpc) 'mass function' and large-scale (r(p) > 3.0 h(-1) Mpc) 'halo-mass cross-correlation' regimes of Delta Sigma have comparable constraining power, allowing internal consistency tests from such an analysis.
    • Metal-enriched Galaxies in the First ∼1 Billion Years: Evidence of a Smooth Metallicity Evolution at z ∼ 5

      Poudel, Suraj; Kulkarni, Varsha P; Cashman, Frances H; Frye, Brenda; Péroux, Céline; Rahmani, Hadi; Quiret, Samuel; Univ Arizona, Dept Astron; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2019-10-30)
      We present seven new abundance measurements of the elements O, C, and Si at z > 4.5, doubling the existing sample of weakly depleted elements in gas-rich galaxies, in order to constrain the first similar to 1 billion years of cosmic metal evolution. These measurements are based on quasar spectra of damped Lyman alpha absorbers (DLAs) and sub-DLAs obtained with the Magellan Inamori Kyocera Echelle (MIKE) and Magellan Echellette (MagE) spectrographs on Magellan-South, and the X-Shooter spectrograph on the Very Large Telescope. We combine these new measurements with those drawn from the literature to estimate the N-HI-weighted binned mean metallicity of -1.51 +/- 0.18 at z = 4.8. This metallicity value is in excellent agreement with the prediction from lower redshift DLAs, supporting the interpretation that the metallicity evolution is smooth at z similar to 5, rather than showing a sudden decline at z > 4.7. Furthermore, the metallicity evolution trends for the DLAs and sub-DLAs are similar within our uncertainties. We also find that the [C/O] ratios for z similar to 5 DLAs are consistent with those of the very metal-poor DLAs. Additionally, using [C/O] and [Si/O] to constrain the nucleosynthesis models, we estimate that the probability distributions of the progenitor star masses for three relatively metal-poor DLAs are centred around 12-17 M-circle dot. Finally, the z similar to 5 absorbers show a different metallicity-velocity dispersion relation than lower redshift DLAs, suggesting that they may be tracing a different population of galaxies.
    • The Stellar Population of Metal-Poor Galaxies at z ≈ 0.8 and the Evolution of the Mass–Metallicity Relation

      Weldon, Andrew; Ly, Chun; Cooper, Michael; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2019-11-04)
      We present results from deep Spitzer/Infrared Array Camera (IRAC) observations of 28 metal-poor, strongly star-forming galaxies selected from the DEEP2 Galaxy Survey. By modelling infrared and optical photometry, we derive stellar masses and other stellar properties. We determine that these metal-poor galaxies have low stellar masses, M-* approximate to 10(8.1)-10(9.5) M-circle dot. Combined with the Balmer-derived star formation rates (SFRs), these galaxies have average inverse SFR/M-* of approximate to 100 Myr. The evolution of stellar mass-gas metallicity relation to z approximate to 0.8 is measured by combining the modelled masses with previously obtained spectroscopic measurements of metallicity from [O III] lambda 4363 detections. Here, we include measurements for 79 galaxies from the Metal Abundances across Cosmic Time Survey. Our mass-metallicity relation is lower at a given stellar mass than at z = 0.1 by 0.27 dex. This demonstrates a strong evolution in the mass-metallicity relation, (1+z)(-1.45-0.76+0.61 .) We find that the shape of the z approximate to 0.8 mass-metallicity relation, a steep rise in metallicity at low stellar masses, transitioning to a plateau at higher masses, is consistent with z similar to 0.1 studies. We also compare the evolution in metallicity between z approximate to 0.8 and z similar to 0.1 against recent strong-line diagnostic studies at intermediate redshifts and find good agreement. Specifically, we find that lower mass galaxies (4 x 10(8) M-circle dot) built up their metal content 1.6 times more rapidly than higher mass galaxies (10(10) M-circle dot). Finally, we examine whether the mass-metallicity relation has a secondary dependence on SFR, and statistically concluded that there is no strong secondary dependence for z approximate to 0.8 low-mass galaxies.
    • How well do the spring indices predict phenological activity across plant species?

      Gerst, Katharine L; Crimmins, Theresa M; Posthumus, Erin E; Rosemartin, Alyssa H; Schwartz, Mark D; Univ Arizona, Sch Nat Resources & Environm (SPRINGER, 2020-02-27)
      The spring indices, models that represent the onset of spring season biological activity, were developed using a long-term observational record from the mid-to-late twentieth century of three species of lilacs and honeysuckles contributed by volunteer observers across the nation. The USA National Phenology Network (USA-NPN) produces and freely delivers maps of spring index onset dates at fine spatial scale for the USA. These maps are used widely in natural resource planning and management applications. The extent to which the models represent activity in a broad suite of plant species is not well documented. In this study, we used a rich record of observational plant phenology data (37,819 onset records) collected in recent years (1981-2017) to evaluate how well gridded maps of the spring index models predict leaf and flowering onset dates in (a) 19 species of ecologically important, broadly distributed deciduous trees and shrubs, and (b) the lilac and honeysuckle species used to construct the models. The extent to which the spring indices predicted vegetative and reproductive phenology varied by species and with latitude, with stronger relationships revealed for shrubs than trees and with the Bloom Index compared to the Leaf Index, and reduced concordance between the indices at higher latitudes. These results allow us to use the indices as indicators of when to expect activity across widely distributed species and can serve as a yardstick to assess how future changes in the timing of spring will impact a broad array of trees and shrubs across the USA.
    • Formation of close binaries by disc fragmentation and migration, and its statistical modelling

      Tokovinin, Andrei; Moe, Maxwell; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2019-11-26)
      Joint statistics of periods and mass ratios of close binaries and its dependence on primary mass can be explained by assuming that seed binary companions are formed by disc fragmentation at random intervals during assemblage of stellar mass and migrate inwards as they accrete from the circumbinary disc. A toy model based on simple prescriptions for the companion growth and migration reproduces such aspects of close solar-mass binaries as the distribution of binary periods P, the brown dwarf desert at short P, the nearly uniform distribution of mass ratios, and a population of equal-mass binaries (twins) that decreases linearly in frequency with log P. For massive stars, the model predicts a large fraction of early mergers, a distribution of log P with a negative slope, and a mass-ratio distribution that is also uniform but with a substantially reduced twin fraction. By treating disc fragmentation as a stochastic process, we also reproduce the observed properties of compact triples. Success of our toy model suggests that most close binaries and compact triples indeed formed by disc fragmentation followed by accretion-driven inward migration.
    • Spectral library of age-benchmark low-mass stars and brown dwarfs

      Manjavacas, E; Lodieu, N; Béjar, V J S; Zapatero-Osorio, M R; Boudreault, S; Bonnefoy, M; Univ Arizona, Steward Observ, Dept Astron (OXFORD UNIV PRESS, 2019-12-27)
      In recent years, some extremely red brown dwarfs have been discovered. They were believed to have a low surface gravity, but many of their spectral characteristics are similar to those of high-surface-gravity brown dwarfs, showing that the spectral characteristics of young brown dwarfs are poorly understood. We aim to test surface-gravity indicators in late-M and early-L brown dwarf spectra using data obtained with the X-shooter spectrograph at the Very Large Telescope. We select a benchmark sample of brown dwarf members ofChamaeleon I (similar to 2 Myr), Upper Scorpius (5-10 Myr), the Pleiades (132 +/- 27 Myr) and Praesepe (590-790 Myr) with well-constrained ages and similar metallicities. We provide a consistent spectral classification of the sample in the optical and in the near-infrared. We measure the equivalent widths of their alkali lines, finding that they have a moderate correlation with age, especially for objects with spectral types M8 and later. We use spectral indices defined in the literature to estimate surface gravity, finding that their gravity assignment is accurate for 75 per cent of our sample. We investigate the correlation between red colour and age, finding that after similar to 10 Myr, the colour does not change significantly for our sample with spectral types M6.0-L3.0. In this case, the red colours might be associated with circumstellar discs, ring structures, extinction, or viewing angle. Finally, we calculate the bolometric luminosity, and J and K bolometric corrections for our sample. We find that six objects are overluminous compared with other members of the same association. These objects are flagged as binary candidates by the Gaia survey.
    • Understanding extreme quasar optical variability with CRTS - II. Changing-state quasars

      Graham, Matthew J; Ross, Nicholas P; Stern, Daniel; Drake, Andrew J; McKernan, Barry; Ford, K E Saavik; Djorgovski, S G; Mahabal, Ashish A; Glikman, Eilat; Larson, Steve; et al. (OXFORD UNIV PRESS, 2019-11-20)
      We present the results of a systematic search for quasars in the Catalina Real-time Transient Survey exhibiting both strong photometric variability and spectroscopic variability over a decadal baseline. We identify 111 sources with specific patterns of optical and mid-infrared photometric behaviour and a defined spectroscopic change. These 'changing-state' quasars (CSQs) form a higher luminosity sample to complement existing sets of 'changing-look' AGNs and quasars in the literature. The CSQs (by selection) exhibit larger photometric variability than the changing-look quasars (CLQs). The spectroscopic variability is marginally stronger in the CSQs than CLQs as defined by the change in H beta/[O III] ratio. We find 48 sources with declining H beta flux and 63 sources with increasing H beta flux, and discover 8 sources with z > 0.8, further extending the redshift arm. Our CSQ sample compares to the literature CLQ objects in similar distributions of H beta flux ratios and differential Eddington ratios between high (bright) and low (dim) states. Taken as a whole, we find that this population of extreme varying quasars is associated with changes in the Eddington ratio and the time-scales imply cooling/heating fronts propagating through the disc.
    • Significant luminosity differences of two twin Type Ia supernovae

      Foley, Ryan J; Hoffmann, Samantha L; Macri, Lucas M; Riess, Adam G; Brown, Peter J; Filippenko, Alexei V; Graham, Melissa L; Milne, Peter A; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2019-11-28)
      The Type Ia supernovae (SNe Ia) 2011by, hosted in NGC 3972, and 2011fe, hosted in M101, are optical 'twins,' having almost identical optical light-curve shapes, colours, and near-maximum-brightness spectra. However, SN 2011fe had significantly more ultraviolet (UV; 1600 < lambda < 2500 angstrom) flux than SN 2011by before and at peak luminosity. Several theoretical models predict that SNe Ia with higher progenitor metallicity should (1) have additional UV opacity and thus lower UV flux; (2) have an essentially unchanged optical spectral-energy distribution; (3) have a similar optical light-curve shape; and (4) because of the excess neutrons, produce more stable Fe-group elements at the expense of radioactive Ni-56 and thus have a lower peak luminosity. Following these predictions, Foley and Kirshner suggested that the difference in UV flux between SNe 2011by and 2011fe was the result of their progenitors having significantly different metallicities. They also measured a large, but insignificant, difference between the peak absolute magnitudes of the SNe (Delta M-V,M- peak = 0.60 +/- 0.36 mag), with SN 2011fe being more luminous. We present a new Cepheid-based distance to NGC 3972, substantially improving the precision of the distance measurement for SN 2011by. With these new data, we determine that the SNe have significantly different peak luminosities (Delta M-V,M- peak = 0.335 +/- 0.069 mag). Consequently, SN 2011fe produced 38 per cent more Ni-56 than SN 2011by, consistent with predictions for progenitor metallicity differences for these SNe, although alternative models may also explain this difference. We discuss how progenitor metallicity differences can contribute to the intrinsic scatter for light-curve-shape-corrected SN luminosities, the use of 'twin' SNe for measuring distances, and implications for using SNe Ia for constraining cosmological parameters.
    • The growth of brightest cluster galaxies and intracluster light over the past 10 billion years

      DeMaio, Tahlia; Gonzalez, Anthony H; Zabludoff, Ann; Zaritsky, Dennis; Aldering, Greg; Brodwin, Mark; Connor, Thomas; Donahue, Megan; Hayden, Brian; Mulchaey, John S; et al. (OXFORD UNIV PRESS, 2019-11-23)
      We constrain the evolution of the brightest cluster galaxy plus intracluster light (BCG + ICL) using an ensemble of 42 galaxy groups and clusters that span redshifts of z = 0.05-1.75 and masses of M-500,M-c = 2 x 10(13)-10(15) M-circle dot. Specifically, we measure the relationship between the BCG + ICL stellar mass M-star and M-500,M-c at projected radii 10 < r < 100 kpc for three different epochs. At intermediate redshift ((z) over bar = 0.40), where we have the best data, we find M-star M-500,c(0.48 +/- 0.06). Fixing the exponent of this power law for all redshifts, we constrain the normalization of this relation to be 2.08 +/- 0.21 times higher at (z) over bar = 0.40 than at high redshift ((z) over bar = 1.55). We find no change in the relation from intermediate to low redshift ((z) over bar = 0.10). In other words, for fixed M-500,M-c, M-star at 10 < r < 100 kpc increases from (z) over bar = 1.55 to (z) over bar = 0.40 and not significantly thereafter. Theoretical models predict that the physical mass growth of the cluster from z = 1.5 to z = 0 within r(500,c) is 1.4x, excluding evolution due to definition of r(500,c). We find that M-star within the central 100 kpc increases by similar to 3.8x over the same period. Thus, the growth of M-star in this central region is more than a factor of 2 greater than the physical mass growth of the cluster as a whole. Furthermore, the concentration of the BCG + ICL stellar mass, defined by the ratio of stellar mass within 10 kpc to the total stellar mass within 100 kpc, decreases with increasing M-500,M-c at all z. We interpret this result as evidence for inside-out growth of the BCG + ICL over the past 10 Gyr, with stellar mass assembly occurring at larger radii at later times.
    • Mixed Messages: II. Outcomes Associated with the Proportion and Placement of Negative Statements in Support Messages

      Ray, Colter D; Harvey, Jacquelyn; Floyd, Kory; Bonito, Joseph A; Reblin, Maija; Univ Arizona, Dept Commun (ROUTLEDGE JOURNALS, TAYLOR & FRANCIS LTD, 2020-02-17)
      Few studies on emotional support have investigated mixed messages - instances when emotional support messages contain both positive and negative statements. Although researchers have recognized that mixed messages occur, most supportive communication research has ignored these ambivalent messages. We contend based on the negativity bias that the more negative statements that occur in an emotional support message, the less effective the message is. To test this possibility, we presented cancer patients (N = 417) with messages that consisted of 0%, 20%, 40%, 60%, or 80% negative statements. Patients rated the messages on five variables: message effectiveness, affective improvement, supporter competence, likelihood to seek future support, and being better off if the supporter had said nothing. A significant positive linear trend occurred for all five variables. The results suggest that the presence and amount of negative statements within an emotional support message has a considerable influence on the recipient's perception of the message and supporter. From a practical standpoint, the results suggest that cancer patients' supporters should act cautiously when communicating negative statements within supportive messages, as even a brief negative statement may cause irreparable damage to the overall quality of a support message.
    • When galaxies align: intrinsic alignments of the progenitors of elliptical galaxies in the Horizon-AGN simulation

      Bate, James; Chisari, Nora Elisa; Codis, Sandrine; Martin, Garreth; Dubois, Yohan; Devriendt, Julien; Pichon, Christophe; Slyz, Adrianne; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2019-11-18)
      Elliptical galaxies today appear aligned with the large-scale structure of the Universe, but it is still an open question when they acquire this alignment. Observational data are currently insufficient to provide constraints on the time evolution of intrinsic alignments, and hence existing models range from assuming that galaxies gain some primordial alignment at formation, to suggesting that they react instantaneously to tidal interactions with the large-scale structure. Using the cosmological hydrodynamical simulation Horizon-AGN, we measure the relative alignments between the major axes of galaxies and eigenvectors of the tidal field as a function of redshift. We focus on constraining the time evolution of the alignment of the main progenitors of massive z = 0 elliptical galaxies, the main weak-lensing contaminant at low redshift. We show that this population, which at z = 0 has a stellar mass above 10(10.4) M-circle dot, transitions from having no alignment with the tidal field at z = 3, to a significant alignment by z = 1. From z = 0.5, they preserve their alignment at an approximately constant level until z = 0. We find a mass dependence of the alignment signal of elliptical progenitors, whereby ellipticals that are less massive today (10(10.4) < M/M-circle dot < 10(10.7)) do not become aligned till later redshifts (z < 2), compared to more massive counterparts. We also present an extended study of progenitor alignments in the parameter space of stellar mass and galaxy dynamics, the impact of shape definition, and tidal field smoothing.
    • Lasting peace or temporary calm? Rebel group decapitation and civil war outcomes

      Ryckman, Kirssa Cline; Univ Arizona, Sch Govt & Publ Policy (SAGE Publications, 2017-09-18)
      Existing research has found that killing or capturing rebel group leaders can lead to the termination of civil wars. This paper considers the quality of those terminations, examining how wars end and whether this produces a lasting peace or only a temporary reprieve from violence. Decapitation is expected to weaken rebel groups, shifting the balance of power to the government; however, results suggest that killing or capturing a rebel group leader tends to produce termination through inactivity rather than outright government victories. Decapitation is also found to have no effect on the chances of civil war recurrence. This suggests that the removal of rebel group leaders is effective primarily as a short-term strategy that does not tend to generate a lasting peace.
    • Magnitude of and Characteristics Associated With the Treatment of Calcium Channel Blocker-Induced Lower-Extremity Edema With Loop Diuretics

      Vouri, Scott Martin; Jiang, Xinyi; Manini, Todd M; Solberg, Laurence M; Pepine, Carl; Malone, Daniel C; Winterstein, Almut G; Univ Arizona, Coll Pharm, Dept Pharm Practice & Sci (AMER MEDICAL ASSOC, 2019-12-02)
      IMPORTANCE Calcium channel blockers, specifically dihydropyridine calcium channel blockers (DH CCBs, eg, amlodipine), may cause lower-extremity edema. Anecdotal reports suggest this may result in a prescribing cascade, where DH CCB-induced edema is treated with loop diuretics. OBJECTIVE To assess the magnitude and characteristics of the DH CCB prescribing cascade. DESIGN, SETTING, AND PARTICIPANTS This cohort study used a prescription sequence symmetry analysis to assess loop diuretic initiation before and after the initiation of DH CCBs among patients aged 20 years or older without heart failure. Data from a private insurance claims database from 2005 to 2017 was analyzed. Use of loop diuretics associated with initiation of angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and other commonly used medications was used as negative controls. Data were analyzed from March 2019 through October 2019. EXPOSURES Initiation of DH CCB or negative control medications. MAIN OUTCOMES AND MEASURES The temporality of loop diuretic initiation relative to DH CCB or negative control initiation. Secular trend-adjusted sequence ratios (aSRs) with 95% CIs were calculated using data from 360 days before and after initiation of DH CCBs. RESULTS Among 1 206 093 DH CCB initiators, 55 818 patients (4.6%) (33 100 [59.3%] aged <65 years; 32 916 [59.0%] women) had a new loop diuretic prescription 360 days before or after DH CCB initiation, resulting in an aSR of 1.87 (95% CI, 1.84-1.90). An estimated 1.44% of DH CCB initiators experienced the prescribing cascade. The aSR was disproportionately higher among DH CCB initiators who were prescribed high doses (aSR, 2.20; 95% CI, 2.13-2.27), initiated amlodipine (aSR, 1.89; 95% CI, 1.86-1.93), were men (aSR, 1.96; 95% CI, 1.91-2.01), and used fewer antihypertensive classes (aSR, 2.55; 95% CI, 2.47-2.64). The evaluation of ACE inhibitors or ARBs as negative controls suggested hypertension progression may have tempered the incidence of the prescribing cascade (aSR for ACE inhibitors and ARBs, 1.27; 95% CI, 1.24-1.29). CONCLUSIONS AND RELEVANCE This study found an excessive use of loop diuretics following initiation of DH CCBs that cannot be completely explained by secular trends or hypertension progression. The prescribing cascade was more pronounced among those initially prescribed a high dose of DH CCBs.