Palomar 13: An Unusual Stellar System in the Galactic Halo

We have measured Keck/HIRES radial velocities for 30 candidate red giants in the direction of Palomar 13: an object traditionally cataloged as a compact, low-luminosity globular cluster. From a sample of 21 confirmed members, we find a systemic velocity of 24.1 km/s and a projected, intrinsic velocity dispersion of 2.2 km/s. Although small, this dispersion is several times larger than that expected for a globular cluster of this luminosity and central concentration. Taken at face value, this dispersion implies a mass-to-light ratio of ~ 40 (in solar units) based on the best-fit King-Michie model. The surface density profile of Palomar 13 also appears to be anomalous among Galactic globular clusters -- depending upon the details of background subtraction and model-fitting, Palomar 13 either contains a substantial population of "extra-tidal" stars, or it is far more spatially extended than previously suspected. The full surface density profile is equally well-fit by a King-Michie model having a high concentration and large tidal radius, or by a NFW model. We examine -- and tentatively reject -- a number of possible explanations for the observed characteristics of Palomar 13 (e.g., velocity "jitter" among the red giants, spectroscopic binary stars, non-standard mass functions, modified Newtonian dynamics), and conclude that the two most plausible scenarios are either catastrophic heating during a recent perigalacticon passage, or the presence of a massive dark halo. Thus, the available evidence suggests that Palomar 13 is either a globular cluster which is now in the process of dissolving into the Galactic halo, or a faint, dark-matter-dominated stellar system (ABRIDGED).Comment: 31 pages, 13 postscript figures and 1 color gif image. Also available at http://www.physics.rutgers.edu/ast/ast-rap.html. Accepted for publication in the Astrophysical Journa

Andes Basin Focal Project

The CPWF Basin Focal Project for the Andes system of basins worked with a range of local stakeholders to develop a better understanding of the mechanisms for improving the productivity of water in the Andes. We considered productivity in broad terms as the productivity of energy (HEP), food and fiber (agriculture) and livelihoods (industry, transport and benefit sharing such as Payments for Environmental Services schemes (PES)). In addition to the compiled data bases and analyses on poverty and institutions, one of the key deliverables of the project was the development and deployment of the AguAAndes policy support system (PSS). This integrates analyses of water availability and productivity within the local environmental and policy context. It is a web-based policy support system combining an extensive spatial database with process-based models for hydrology, crop production and socio-economic processes. It is intended to allow analysts and decision makers to test the potential onsite and offsite impacts of land and water management decisions in terms of their ability to sustain environmental services and human wellbeing. Interventions and recommendations for future actions on water and food in the region are presented

Optical characterization of porous alumina from vacuum ultraviolet to mid-infrared

Porous alumina was fabricated and optically characterized over a wide spectral range. Layers were formed electrochemically in oxalic acid solution from 10-μm-thick aluminum films evaporated onto silicon wafers. The layer formation was monitored with in situ spectroscopic ellipsometry in the visible and near-infrared wavelength range to accurately determine the thickness and dielectric functions. Anisotropy due to the columnar nature of the porous structure was determined using optical modeling. The porous alumina layer was found to have a small but significant absorption tail throughout the visible region. Atomic force microscopy and scanning electron microscopy were used throughout the process to assess the quality of pore formation. The mean pore center-to-center spacing was approximately 100 nm with thicknesses up to 5 μm. The infrared spectra revealed absorption peaks previously seen in ceramic alumina and peaks not associated with bulk alumina

The 2HWC HAWC Observatory Gamma Ray Catalog

We present the first catalog of TeV gamma-ray sources realized with the recently completed High Altitude Water Cherenkov Observatory (HAWC). It is the most sensitive wide field-of-view TeV telescope currently in operation, with a 1-year survey sensitivity of ~5-10% of the flux of the Crab Nebula. With an instantaneous field of view >1.5 sr and >90% duty cycle, it continuously surveys and monitors the sky for gamma ray energies between hundreds GeV and tens of TeV. HAWC is located in Mexico at a latitude of 19 degree North and was completed in March 2015. Here, we present the 2HWC catalog, which is the result of the first source search realized with the complete HAWC detector. Realized with 507 days of data and represents the most sensitive TeV survey to date for such a large fraction of the sky. A total of 39 sources were detected, with an expected contamination of 0.5 due to background fluctuation. Out of these sources, 16 are more than one degree away from any previously reported TeV source. The source list, including the position measurement, spectrum measurement, and uncertainties, is reported. Seven of the detected sources may be associated with pulsar wind nebulae, two with supernova remnants, two with blazars, and the remaining 23 have no firm identification yet.Comment: Submitted 2017/02/09 to the Astrophysical Journa

The Sensitivity of HAWC to High-Mass Dark Matter Annihilations

The High Altitude Water Cherenkov (HAWC) observatory is a wide field-of-view detector sensitive to gamma rays of 100 GeV to a few hundred TeV. Located in central Mexico at 19 degrees North latitude and 4100 m above sea level, HAWC will observe gamma rays and cosmic rays with an array of water Cherenkov detectors. The full HAWC array is scheduled to be operational in Spring 2015. In this paper, we study the HAWC sensitivity to the gamma-ray signatures of high-mass (multi- TeV) dark matter annihilation. The HAWC observatory will be sensitive to diverse searches for dark matter annihilation, including annihilation from extended dark matter sources, the diffuse gamma-ray emission from dark matter annihilation, and gamma-ray emission from non-luminous dark matter subhalos. Here we consider the HAWC sensitivity to a subset of these sources, including dwarf galaxies, the M31 galaxy, the Virgo cluster, and the Galactic center. We simulate the HAWC response to gamma rays from these sources in several well-motivated dark matter annihilation channels. If no gamma-ray excess is observed, we show the limits HAWC can place on the dark matter cross-section from these sources. In particular, in the case of dark matter annihilation into gauge bosons, HAWC will be able to detect a narrow range of dark matter masses to cross-sections below thermal. HAWC should also be sensitive to non-thermal cross-sections for masses up to nearly 1000 TeV. The constraints placed by HAWC on the dark matter cross-section from known sources should be competitive with current limits in the mass range where HAWC has similar sensitivity. HAWC can additionally explore higher dark matter masses than are currently constrained.Comment: 15 pages, 4 figures, version to be published in PR

First Results from High Angular Resolution ALMA Observations Toward the HL Tau Region

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations from the 2014 Long Baseline Campaign in dust continuum and spectral line emission from the HL Tau region. The continuum images at wavelengths of 2.9, 1.3, and 0.87 mm have unprecedented angular resolutions of 0.075 arcseconds (10 AU) to 0.025 arcseconds (3.5 AU), revealing an astonishing level of detail in the circumstellar disk surrounding the young solar analogue HL Tau, with a pattern of bright and dark rings observed at all wavelengths. By fitting ellipses to the most distinct rings, we measure precise values for the disk inclination (46.72pm0.05 degrees) and position angle (+138.02pm0.07 degrees). We obtain a high-fidelity image of the 1.0 mm spectral index ($\alpha$), which ranges from $\alpha\sim2.0$ in the optically-thick central peak and two brightest rings, increasing to 2.3-3.0 in the dark rings. The dark rings are not devoid of emission, we estimate a grain emissivity index of 0.8 for the innermost dark ring and lower for subsequent dark rings, consistent with some degree of grain growth and evolution. Additional clues that the rings arise from planet formation include an increase in their central offsets with radius and the presence of numerous orbital resonances. At a resolution of 35 AU, we resolve the molecular component of the disk in HCO+ (1-0) which exhibits a pattern over LSR velocities from 2-12 km/s consistent with Keplerian motion around a ~1.3 solar mass star, although complicated by absorption at low blue-shifted velocities. We also serendipitously detect and resolve the nearby protostars XZ Tau (A/B) and LkHa358 at 2.9 mm.Comment: 11 pages, 5 figures, 2 tables, accepted for publication in the Astrophysical Journal Letter

Differential effect of obesity on bone mineral density in White, Hispanic and African American women: a cross sectional study

Osteoporosis is a major public health problem with low bone mass affecting nearly half the women aged 50 years or older. Evidence from various studies has shown that higher body mass index (BMI) is a protective factor for bone mineral density (BMD). Most of the evidence, however, is from studies with Caucasian women and it is unclear to what extent ethnicity plays a role in modifying the effect of BMI on BMD. A cross sectional study was performed in which records of postmenopausal women who presented for screening for osteoporosis at 2 urban medical centres were reviewed. Using logistic regression, we examined the interaction of race and BMI after adjusting for age, family history of osteoporosis, maternal fracture, smoking, and sedentary lifestyle on BMD. Low BMD was defined as T-score at the lumbar spine < -1. Among 3,206 patients identified, the mean age of the study population was 58.3 ± 0.24 (Years ± SEM) and the BMI was 30.6 kg/m(2). 2,417 (75.4%) were African Americans (AA), 441(13.6%) were Whites and 348 (10.9%) were Hispanics. The AA women had lower odds of having low BMD compared to Whites [Odds ratio (OR) = 0.079 (0.03–0.24) (95% CI), p < 0.01]. The odds ratio of low BMD was not statistically significant between White and Hispanic women. We examined the interaction between race and BMD. For White women; as the BMI increases by unity, the odds of low BMD decreases [OR = 0.9 (0.87–0.94), p < 0.01; for every unit increase in BMI]. AA women had slightly but significantly higher odds of low BMD compared to Whites [OR 1.015 (1.007–1.14), p <0.01 for every unit increase in BMI]. This effect was not observed when Hispanic women were compared to Whites. There is thus a race-dependent effect of BMI on BMD. With each unit increase in BMI, BMD increases for White women, while a slight but significant decrease in BMD occurs in African American women

First month prednisone dose predicts prednisone burden during the following 11 months: An observational study from the RELES cohort

Aim: To study the influence of prednisone dose during the first month after systemic lupus erythematosus (SLE) diagnosis (prednisone-1) on glucocorticoid burden during the subsequent 11 months (prednisone-2–12). Methods: 223 patients from the Registro Español de Lupus Eritematoso Sistémico inception cohort were studied. The cumulative dose of prednisone-1 and prednisone-2–12 were calculated and recoded into a four-level categorical variable: no prednisone, low dose (up to 7.5 mg/day), medium dose (up to 30 mg/day) and high dose (over 30 mg/day). The association between the cumulative prednisone-1 and prednisone-2–12 doses was tested. We analysed whether the four-level prednisone-1 categorical variable was an independent predictor of an average dose >7.5 mg/day of prednisone-2–12. Adjusting variables included age, immunosuppressives, antimalarials, methyl-prednisolone pulses, lupus nephritis and baseline SLE Disease Activity Index (SLEDAI). Results: Within the first month, 113 patients (51%) did not receive any prednisone, 24 patients (11%) received average low doses, 46 patients (21%) received medium doses and 40 patients (18%) received high doses. There was a strong association between prednisone-1 and prednisone-2–12 dose categories (p7.5 mg/day, while patients receiving low-dose prednisone-1 were not (adjusted OR 1.4, 95% CI 0. 0.38 to 5.2). If the analysis was restricted to the 158 patients with a baseline SLEDAI of =6, the model did not change. Conclusion: The dose of prednisone during the first month after the diagnosis of SLE is an independent predictor of prednisone burden during the following 11 months