264 research outputs found

    ASCA and contemporaneous ground-based observations of the BL Lacertae objects 1749+096 and 2200+420 (BL Lac)

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    We present ASCA observations of the radio-selected BL Lacertae objects 1749+096 (z=0.32) and 2200+420 (BL Lac, z=0.069) performed in 1995 Sept and Nov, respectively. The ASCA spectra of both sources can be described as a first approximation by a power law with photon index Gamma ~ 2. This is flatter than for most X-ray-selected BL Lacs observed with ASCA, in agreement with the predictions of current blazar unification models. While 1749+096 exhibits tentative evidence for spectral flattening at low energies, a concave continuum is detected for 2200+420: the steep low-energy component is consistent the high-energy tail of the synchrotron emission responsible for the longer wavelengths, while the harder tail at higher energies is the onset of the Compton component. The spectral energy distributions from radio to gamma-rays are consistent with synchrotron-self Compton emission from a single homogeneous region shortward of the IR/optical wavelengths, with a second component in the radio domain related to a more extended emission region. For 2200+420, comparing the 1995 Nov state with the optical/GeV flare of 1997 July, we find that models requiring inverse Compton scattering of external photons provide a viable mechanism for the production of the highest (GeV) energies during the flare. An increase of the external radiation density and of the power injected in the jet can reproduce the flat gamma-ray continuum observed in 1997 July. A directly testable prediction of this model is that the line luminosity in 2200+420 should vary shortly after (~1 month) a non-thermal synchrotron flare.Comment: 28 pages,6 figures, 5 tables; LaTeX document. accepted for publication in the Astrophysical Journa

    The Hubble Ultra Deep Field

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    This paper presents the Hubble Ultra Deep Field (HUDF), a one million second exposure of an 11 square minute-of-arc region in the southern sky with the Hubble Space Telescope. The exposure time was divided among four filters, F435W (B435), F606W (V606), F775W (i775), and F850LP (z850), to give approximately uniform limiting magnitudes mAB~29 for point sources. The image contains at least 10,000 objects presented here as a catalog. Few if any galaxies at redshifts greater than ~4 resemble present day spiral or elliptical galaxies. Using the Lyman break dropout method, we find 504 B-dropouts, 204 V-dropouts, and 54 i-dropouts. Using these samples that are at different redshifts but derived from the same data, we find no evidence for a change in the characteristic luminosity of galaxies but some evidence for a decrease in their number densities between redshifts of 4 and 7. The ultraviolet luminosity density of these samples is dominated by galaxies fainter than the characteristic luminosity, and the HUDF reveals considerably more luminosity than shallower surveys. The apparent ultraviolet luminosity density of galaxies appears to decrease from redshifts of a few to redshifts greater than 6. The highest redshift samples show that star formation was already vigorous at the earliest epochs that galaxies have been observed, less than one billion years after the Big Bang.Comment: 44 pages, 18 figures, to appear in the Astronomical Journal October 200

    High-resolution mapping of losses and gains of Earth’s tidal wetlands

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    Tidal wetlands are expected to respond dynamically to global environmental change, but the extent to which wetland losses have been offset by gains remains poorly understood. We developed a global analysis of satellite data to simultaneously monitor change in three highly interconnected intertidal ecosystem types—tidal flats, tidal marshes, and mangroves—from 1999 to 2019. Globally, 13,700 square kilometers of tidal wetlands have been lost, but these have been substantially offset by gains of 9700 km2, leading to a net change of −4000 km2 over two decades. We found that 27% of these losses and gains were associated with direct human activities such as conversion to agriculture and restoration of lost wetlands. All other changes were attributed to indirect drivers, including the effects of coastal processes and climate change

    Mental, social, and physical well-being in New Hampshire, Oregon, and Washington, 2010 Behavioral Risk Factor Surveillance System: implications for public health research and practice related to Healthy People 2020 foundation health measures on well-being

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    BACKGROUND: Well-being is now accepted as one of four cross-cutting measures in gauging progress for Healthy People 2020. This shift to population indicators of well-being redresses notions of health that have focused on absence of illness (negative health) as a primary or sufficient indicator of positive functioning. The purpose of this study was to estimate mental, social, and physical well-being in three US states using new measures piloted on the 2010 Behavioral Risk Factor Surveillance Survey System (BRFSS). Baseline estimates were provided for states overall, and within states for demographic subgroups, those with chronic health conditions or disabilities, and those with behavioral risk factors. METHODS: Ten validated questions designed to assess mental (e.g., satisfaction with life, satisfaction with life domains, happiness), physical (e.g., satisfaction with energy level), and social dimensions (e.g., frequency of social support) of well-being were selected with state input for inclusion on BRFSS. 18,622 individuals responded to the BRFSS surveys administered by New Hampshire (N = 3,139), Oregon (N = 2,289), and Washington (N = 13,194). Multivariate adjusted proportions of positive responses to well-being items were examined. RESULTS: After adjustment for confounders, about 67% of adults in these states had high levels of well-being, including >80% reporting experiencing happiness. Most adults were satisfied with their work, neighborhood, and education, but significant differences were seen in subgroups. Well-being differed by demographic characteristics such as marital status, health behaviors, chronic conditions, and disability status, with those who reported a disability and smokers consistently experiencing the worst well-being. CONCLUSIONS: Well-being is accepted as one of four cross-cutting measures in gauging progress for Healthy People 2020. Well-being differs by important sociodemographic factors and health conditions (e.g., age, employment, smoking, disability status). These findings provide baseline estimates for the three states to use in gauging improvements in well-being and can serve as a model for other state-level or national surveillance systems. These findings also assist states in identifying vulnerable subgroups who may benefit from potential interventions such as those in the National Prevention Strategy that focus on enhancing well-being where such disparities exist

    Astro2020 Science White Paper: Triggered High-Priority Observations of Dynamic Solar System Phenomena

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    Unexpected dynamic phenomena have surprised solar system observers in the past and have led to important discoveries about solar system workings. Observations at the initial stages of these events provide crucial information on the physical processes at work. We advocate for long-term/permanent programs on ground-based and space-based telescopes of all sizes - including Extremely Large Telescopes (ELTs) - to conduct observations of high-priority dynamic phenomena, based on a predefined set of triggering conditions. These programs will ensure that the best initial dataset of the triggering event are taken; separate additional observing programs will be required to study the temporal evolution of these phenomena. While not a comprehensive list, the following are notional examples of phenomena that are rare, that cannot be anticipated, and that provide high-impact advances to our understandings of planetary processes. Examples include: new cryovolcanic eruptions or plumes on ocean worlds; impacts on Jupiter, Saturn, Uranus, or Neptune; extreme eruptions on Io; convective superstorms on Saturn, Uranus, or Neptune; collisions within the asteroid belt or other small-body populations; discovery of an interstellar object passing through our solar system (e.g. 'Oumuamua); and responses of planetary atmospheres to major solar flares or coronal mass ejections.Comment: Astro2020 white pape

    Review of the influence of farrowing and lactation housing and positive human contact on sow and piglet welfare

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    Farrowing crates continue to be the most common system of housing farrowing and lactating sows, however continuous confinement is one of the most contentious welfare issues in livestock production. This review aims to critically evaluate the scientific literature on the implications of two important determinants of sow and piglet welfare: housing and human contact. While the evidence in sows is contradictory, there is consistent evidence of a greater short-term cortisol response in gilts introduced to farrowing crates than pens and there is limited evidence of changes in the HPA axis consistent with sustained stress in gilts during the fourth week of lactation. Confinement of sows during lactation increases stereotypic behaviour, reduces sow-piglet interactions, nursing duration and lying behaviour, and may contribute to leg and shoulder injuries in sows. Piglets reared by sows in pens display more play and less oral manipulative behaviours and generally have better growth rates than those reared in farrowing crates. However, there is increasing interest in developing alternate housing systems with minimal sow confinement and reduced piglet mortality risk. Recent research on temporary crating of sows suggests that confinement briefly around farrowing may be the best compromise between continuous housing in farrowing crates and pens, as it may reduce live-born piglet mortality, while providing the opportunity for the sow to move more freely prior to parturition. Together with housing, the behaviour of stockpeople is a key determinant of pig welfare. Recent evidence shows that positive handling of piglets during lactation reduces fear behaviour and physiological stress responses of pigs to humans, novelty and routine husbandry practices, and thus may be enriching for piglets. As a source of enrichment, positive human interactions provide several advantages: close interactions with piglets usually occur several times daily, positive interactions can be combined with routine checks, human interactions invariably provide variability in their predictability which will minimise habituation, and positive interactions may not require additional physical resources. There is a clear need for comprehensive research examining both the short- and long-term welfare implications and the practicality of less confinement of the sow, and positive handling of both sows and piglets during lactation

    The Atacama Cosmology Telescope: Data Characterization and Map Making

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    We present a description of the data reduction and mapmaking pipeline used for the 2008 observing season of the Atacama Cosmology Telescope (ACT). The data presented here at 148 GHz represent 12% of the 90 TB collected by ACT from 2007 to 2010. In 2008 we observed for 136 days, producing a total of 1423 hours of data (11 TB for the 148 GHz band only), with a daily average of 10.5 hours of observation. From these, 1085 hours were devoted to a 850 deg^2 stripe (11.2 hours by 9.1 deg) centered on a declination of -52.7 deg, while 175 hours were devoted to a 280 deg^2 stripe (4.5 hours by 4.8 deg) centered at the celestial equator. We discuss sources of statistical and systematic noise, calibration, telescope pointing, and data selection. Out of 1260 survey hours and 1024 detectors per array, 816 hours and 593 effective detectors remain after data selection for this frequency band, yielding a 38% survey efficiency. The total sensitivity in 2008, determined from the noise level between 5 Hz and 20 Hz in the time-ordered data stream (TOD), is 32 micro-Kelvin sqrt{s} in CMB units. Atmospheric brightness fluctuations constitute the main contaminant in the data and dominate the detector noise covariance at low frequencies in the TOD. The maps were made by solving the least-squares problem using the Preconditioned Conjugate Gradient method, incorporating the details of the detector and noise correlations. Cross-correlation with WMAP sky maps, as well as analysis from simulations, reveal that our maps are unbiased at multipoles ell > 300. This paper accompanies the public release of the 148 GHz southern stripe maps from 2008. The techniques described here will be applied to future maps and data releases.Comment: 20 pages, 18 figures, 6 tables, an ACT Collaboration pape

    The Atacama Cosmology Telescope: Cosmological parameters from three seasons of data

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    We present constraints on cosmological and astrophysical parameters from high-resolution microwave background maps at 148 GHz and 218 GHz made by the Atacama Cosmology Telescope (ACT) in three seasons of observations from 2008 to 2010. A model of primary cosmological and secondary foreground parameters is fit to the map power spectra and lensing deflection power spectrum, including contributions from both the thermal Sunyaev-Zeldovich (tSZ) effect and the kinematic Sunyaev-Zeldovich (kSZ) effect, Poisson and correlated anisotropy from unresolved infrared sources, radio sources, and the correlation between the tSZ effect and infrared sources. The power ell^2 C_ell/2pi of the thermal SZ power spectrum at 148 GHz is measured to be 3.4 +\- 1.4 muK^2 at ell=3000, while the corresponding amplitude of the kinematic SZ power spectrum has a 95% confidence level upper limit of 8.6 muK^2. Combining ACT power spectra with the WMAP 7-year temperature and polarization power spectra, we find excellent consistency with the LCDM model. We constrain the number of effective relativistic degrees of freedom in the early universe to be Neff=2.79 +\- 0.56, in agreement with the canonical value of Neff=3.046 for three massless neutrinos. We constrain the sum of the neutrino masses to be Sigma m_nu < 0.39 eV at 95% confidence when combining ACT and WMAP 7-year data with BAO and Hubble constant measurements. We constrain the amount of primordial helium to be Yp = 0.225 +\- 0.034, and measure no variation in the fine structure constant alpha since recombination, with alpha/alpha0 = 1.004 +/- 0.005. We also find no evidence for any running of the scalar spectral index, dns/dlnk = -0.004 +\- 0.012.Comment: 26 pages, 22 figures. This paper is a companion to Das et al. (2013) and Dunkley et al. (2013). Matches published JCAP versio
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