Century-scale records of land-based activities recorded in Mesoamerican coral cores     

Jessica E. Carilli  Nancy G. Prouty  Konrad A. Hughen  Richard D. Norris 《Marine pollution bulletin》2009,58(12):1835-1842

The Mesoamerican Reef, the second-largest barrier reef in the world, is located in the western Caribbean Sea off the coasts of Mexico, Belize, Guatemala, and Honduras. Particularly in the south, the surrounding watersheds are steep and the climate is extremely wet. With development and agricultural expansion, the potential for negative impacts to the reef from land-based runoff becomes high. We constructed annually resolved century-scale records of metal/calcium ratios in coral skeletons collected from four sites experiencing a gradient of land-based runoff. Our proxy data indicate that runoff onto the reef has increased relatively steadily over time at all sites, consistent with land use trends from historical records. Sediment supply to the reef is greater in the south, and these more exposed reefs will probably benefit most immediately from management that targets runoff reduction. However, because runoff at all sites is steadily increasing, even distal sites will benefit from watershed management.  相似文献   

The AGN/Starburst connection in luminous infrared galaxies     

L.J. Kewley  C.A. Heisler  M.A. Dopita  R.P. Norris 《Astrophysics and Space Science》1999,266(1-2):131-136

We are addressing the issue of whether there exists an evolutionaryconnection between starburst and AGN in luminous infrared galaxies. We are combining theoretical modelling with optical, radio and infrared data from IRAS for a large sample of 285 infrared galaxies with a range ofluminosities. In this paper, we present a comparison between the optical spectroscopic data with the incidence of compact radio cores for a subsample of these galaxies. We find 90% of AGN type galaxies contain compact radio cores, while 37% of starburst galaxies contain compact radio cores. The compact radio cores in the starburst galaxies have a minimum brightness temperature of 3 × 10⁵ K, higher than those of standard extended HII regions and may be obscured AGN or complexes of extremely luminous supernovae such as that seen in Arp 220.  相似文献   

Different Periodicities in the Sunspot Area and the Occurrence of Solar Flares and Coronal Mass Ejections in Solar Cycle 23 – 24     

D. P. Choudhary  J. K. Lawrence  M. Norris  A. C. Cadavid 《Solar physics》2014,289(2):649-656

In order to investigate the relationship between magnetic-flux emergence, solar flares, and coronal mass ejections (CMEs), we study the periodicity in the time series of these quantities. It has been known that solar flares, sunspot area, and photospheric magnetic flux have a dominant periodicity of about 155 days, which is confined to a part of the phase of the solar cycle. These periodicities occur at different phases of the solar cycle during successive phases. We present a time-series analysis of sunspot area, flare and CME occurrence during Cycle 23 and the rising phase of Cycle 24 from 1996 to 2011. We find that the flux emergence, represented by sunspot area, has multiple periodicities. Flares and CMEs, however, do not occur with the same period as the flux emergence. Using the results of this study, we discuss the possible activity sources producing emerging flux.  相似文献   

Development of the Coastal Storm Modeling System (CoSMoS) for predicting the impact of storms on high-energy,active-margin coasts     

Patrick L. Barnard  Maarten van Ormondt  Li H. Erikson  Jodi Eshleman  Cheryl Hapke  Peter Ruggiero  Peter N. Adams  Amy C. Foxgrover 《Natural Hazards》2014,74(2):1095-1125

The Coastal Storm Modeling System (CoSMoS) applies a predominantly deterministic framework to make detailed predictions (meter scale) of storm-induced coastal flooding, erosion, and cliff failures over large geographic scales (100s of kilometers). CoSMoS was developed for hindcast studies, operational applications (i.e., nowcasts and multiday forecasts), and future climate scenarios (i.e., sea-level rise + storms) to provide emergency responders and coastal planners with critical storm hazards information that may be used to increase public safety, mitigate physical damages, and more effectively manage and allocate resources within complex coastal settings. The prototype system, developed for the California coast, uses the global WAVEWATCH III wave model, the TOPEX/Poseidon satellite altimetry-based global tide model, and atmospheric-forcing data from either the US National Weather Service (operational mode) or Global Climate Models (future climate mode), to determine regional wave and water-level boundary conditions. These physical processes are dynamically downscaled using a series of nested Delft3D-WAVE (SWAN) and Delft3D-FLOW (FLOW) models and linked at the coast to tightly spaced XBeach (eXtreme Beach) cross-shore profile models and a Bayesian probabilistic cliff failure model. Hindcast testing demonstrates that, despite uncertainties in preexisting beach morphology over the ~500 km alongshore extent of the pilot study area, CoSMoS effectively identifies discrete sections of the coast (100s of meters) that are vulnerable to coastal hazards under a range of current and future oceanographic forcing conditions, and is therefore an effective tool for operational and future climate scenario planning.  相似文献   

Bipolar outflows in OH/IR stars     

Albert A. Zijlstra  J. M. Chapman  P. te Lintel Hekkert  L. Likkel  F. Comeron  R. P. Norris  F. J. Molster  R. J. Cohen 《Monthly notices of the Royal Astronomical Society》2001,322(2):280-308

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MIGRAT: A COMPUTER-ASSISTED INSTRUCTIONAL PROGRAM FOR THE SIMULATION OF MIGRATION     

Robert E. Norris 《The Professional geographer》1973,25(2):167-168

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Distant field blue horizontal branch stars and the mass of the Galaxy – II. Photometry and spectroscopy of UKST candidates 16 < B < 19.5, 11 < R < 52 kpc     

L. Clewley  S. J. Warren  P. C. Hewett  John E. Norris  N. W. Evans 《Monthly notices of the Royal Astronomical Society》2004,352(1):285-298

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A Collimated Stellar Wind Emanating from a Massive Protostar     

Guido Garay  Kate J. Brooks  Diego Mardones  Ray Norris 《Astrophysics and Space Science》2004,292(1-4):517-523

We report multi-wavelength observations towards IRAS 16547–4247, a luminous infrared source with a bolometric luminosity of 6.2 × 10⁴ L _⊙. Dust continuum observations at 1.2-mm indicate that this object is associated with a dust cloud with a size of about 0.4 pc in diameter and a mass of about 1.3 × 10³ M _⊙. Radio continuum observations show the presence of a triple radio source consisting of a compact central object and two outer lobes, separated by about 0.3 pc, symmetrically located from the central source. Molecular hydrogen line observations show a chain of knots that trace a collimated flow extending over 1.5 pc. We suggest that IRAS 16547–4247 corresponds to a dense massive core which hosts near its central region a high-mass star in an early stage of evolution. This massive YSO is undergoing the ejection of a collimated stellar wind which drives the H₂ flow. The radio emission from the lobes arises in shocks resulting from the interaction of the collimated wind with the surrounding medium. We conclude that the thermal jets found in the formation of low-mass stars are also produced in high-mass stars.  相似文献   

Very long baseline interferometry detection of an Infrared-Faint Radio Source     

Ray P. Norris  Steven Tingay  Chris Phillips  Enno Middelberg  Adam Deller  Philip N. Appleton 《Monthly notices of the Royal Astronomical Society》2007,378(4):1434-1438

Infrared-Faint Radio Sources represent a new and unexpected class of object which is bright at radio wavelengths but unusually faint at infrared wavelengths. If, like most mJy radio sources, they were either conventional active or star-forming galaxies in the local Universe, we would expect them to be detectable at infrared wavelengths, and so their non-detection by the Spitzer Space Telescope is surprising. Here, we report the detection of one of these sources using very long baseline interferometry, from which we conclude that the sources are driven by active galactic nuclei. We suggest that these sources are either normal radio-loud quasars at high redshift or abnormally obscured radio galaxies.  相似文献   

Evolutionary Map of the Universe: Tracing Clusters to High Red-shift     

Ray P. Norris  the EMU Team 《Journal of Astrophysics and Astronomy》2011,32(4):599-607

The Australian SKA Pathfinder (ASKAP) is a new radio-telescope being built in Western Australia. One of the key surveys for which it is being built is EMU (Evolutionary Map of the Universe), which will make a deep (∼10 μJy/bm rms) radio continuum survey covering the entire sky as far North as +30°. EMU may be compared to the NRAO VLA Sky Survey (NVSS), except that it will have about 45 times the sensitivity, and five times the resolution. EMU will also have much better sensitivity to diffuse emission than previous large surveys, and is expected to produce a large catalogue of relics, tailed galaxies, and halos, and will increase the number of known clusters by a significant factor. Here we describe the EMU project and its impact on the astrophysics of clusters.  相似文献