Showing papers by "Jet Propulsion Laboratory published in 2012"
TL;DR: In this paper, the authors demonstrate the ability to multiplex and transfer data between twisted beams of light with different amounts of orbital angular momentum, which provides new opportunities for increasing the data capacity of free-space optical communications links.
Abstract: Researchers demonstrate the ability to multiplex and transfer data between twisted beams of light with different amounts of orbital angular momentum — a development that provides new opportunities for increasing the data capacity of free-space optical communications links.
3,556 citations
University of Leeds1, Jet Propulsion Laboratory2, University of Colorado Boulder3, Technical University of Denmark4, Durham University5, University of Texas at Austin6, Ohio State University7, University College London8, Technische Universität München9, Lamont–Doherty Earth Observatory10, Johns Hopkins University Applied Physics Laboratory11, University of Tasmania12, Newcastle University13, Utrecht University14, University of Kansas15, Swansea University16, Goddard Space Flight Center17, University of Ottawa18, University of California, Irvine19, University of Bristol20, British Antarctic Survey21, University of Innsbruck22, Delft University of Technology23
TL;DR: There is good agreement between different satellite methods—especially in Greenland and West Antarctica—and that combining satellite data sets leads to greater certainty, and the mass balance of Earth’s polar ice sheets is estimated by combining the results of existing independent techniques.
Abstract: We combined an ensemble of satellite altimetry, interferometry, and gravimetry data sets using common geographical regions, time intervals, and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of Earth’s polar ice sheets. We find that there is good agreement between different satellite methods—especially in Greenland and West Antarctica—and that combining satellite data sets leads to greater certainty. Between 1992 and 2011, the ice sheets of Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula changed in mass by –142 ± 49, +14 ± 43, –65 ± 26, and –20 ± 14 gigatonnes year−1, respectively. Since 1992, the polar ice sheets have contributed, on average, 0.59 ± 0.20 millimeter year−1 to the rate of global sea-level rise.
1,215 citations
University of California, Berkeley1, Ames Research Center2, San Jose State University3, Lowell Observatory4, Jet Propulsion Laboratory5, University of Texas at Austin6, Harvard University7, Las Cumbres Observatory Global Telescope Network8, Space Telescope Science Institute9, Niels Bohr Institute10, Aarhus University11, National Center for Atmospheric Research12, NASA Exoplanet Science Institute13, Massachusetts Institute of Technology14, Fermilab15, University of California, Santa Cruz16, Yale University17, University of Florida18, California Institute of Technology19, University of California, Santa Barbara20, University of Hertfordshire21, San Diego State University22, Carnegie Institution for Science23, Lawrence Hall of Science24, Villanova University25
TL;DR: In this paper, the authors report the distribution of planets as a function of planet radius, orbital period, and stellar effective temperature for orbital periods less than 50 days around solar-type (GK) stars.
Abstract: We report the distribution of planets as a function of planet radius, orbital period, and stellar effective temperature for orbital periods less than 50 days around solar-type (GK) stars. These results are based on the 1235 planets (formally "planet candidates") from the Kepler mission that include a nearly complete set of detected planets as small as 2 R_⊕. For each of the 156,000 target stars, we assess the detectability of planets as a function of planet radius, R_p, and orbital period, P, using a measure of the detection efficiency for each star. We also correct for the geometric probability of transit, R_*/a. We consider first Kepler target stars within the "solar subset" having T_eff = 4100-6100 K, log g = 4.0-4.9, and Kepler magnitude K_p 2 R_⊕ we measure an occurrence of less than 0.001 planets per star. For all planets with orbital periods less than 50 days, we measure occurrence of 0.130 ± 0.008, 0.023 ± 0.003, and 0.013 ± 0.002 planets per star for planets with radii 2-4, 4-8, and 8-32 R_⊕, in agreement with Doppler surveys. We fit occurrence as a function of P to a power-law model with an exponential cutoff below a critical period P_0. For smaller planets, P_0 has larger values, suggesting that the "parking distance" for migrating planets moves outward with decreasing planet size. We also measured planet occurrence over a broader stellar T_eff range of 3600-7100 K, spanning M0 to F2 dwarfs. Over this range, the occurrence of 2-4 R_⊕ planets in the Kepler field increases with decreasing T_eff, with these small planets being seven times more abundant around cool stars (3600-4100 K) than the hottest stars in our sample (6600-7100 K).
1,159 citations
University of Sussex1, California Institute of Technology2, Jet Propulsion Laboratory3, European Space Agency4, Ames Research Center5, University of Edinburgh6, Paris Diderot University7, Imperial College London8, University of Paris-Sud9, Aix-Marseille University10, Cornell University11, University of La Laguna12, Spanish National Research Council13, Complutense University of Madrid14, UK Astronomy Technology Centre15, University of Colorado Boulder16, University of California, Irvine17, Goddard Space Flight Center18, University of Nottingham19, Cardiff University20, University of Padua21, Institut d'Astrophysique de Paris22, University of Cambridge23, University of British Columbia24, European Space Research and Technology Centre25, University of Manchester26, University College London27, University of Lethbridge28, Rutherford Appleton Laboratory29, University of Oxford30, Commonwealth Scientific and Industrial Research Organisation31, University of Hertfordshire32, Harvard University33
TL;DR: The Herschel Multi-tiered Extragalactic Survey (HerMES) is a legacy program designed to map a set of nested fields totalling ∼380deg^2 as mentioned in this paper.
Abstract: The Herschel Multi-tiered Extragalactic Survey (HerMES) is a legacy programme designed to map a set of nested fields totalling ∼380 deg^2. Fields range in size from 0.01 to ∼20 deg^2, using the Herschel-Spectral and Photometric Imaging Receiver (SPIRE) (at 250, 350 and 500 μm) and the Herschel-Photodetector Array Camera and Spectrometer (PACS) (at 100 and 160 μm), with an additional wider component of 270 deg^2 with SPIRE alone. These bands cover the peak of the redshifted thermal spectral energy distribution from interstellar dust and thus capture the reprocessed optical and ultraviolet radiation from star formation that has been absorbed by dust, and are critical for forming a complete multiwavelength understanding of galaxy formation and evolution.
The survey will detect of the order of 100 000 galaxies at 5σ in some of the best-studied fields in the sky. Additionally, HerMES is closely coordinated with the PACS Evolutionary Probe survey. Making maximum use of the full spectrum of ancillary data, from radio to X-ray wavelengths, it is designed to facilitate redshift determination, rapidly identify unusual objects and understand the relationships between thermal emission from dust and other processes. Scientific questions HerMES will be used to answer include the total infrared emission of galaxies, the evolution of the luminosity function, the clustering properties of dusty galaxies and the properties of populations of galaxies which lie below the confusion limit through lensing and statistical techniques.
This paper defines the survey observations and data products, outlines the primary scientific goals of the HerMES team, and reviews some of the early results.
852 citations
University of Sussex1, Jet Propulsion Laboratory2, California Institute of Technology3, European Space Agency4, Ames Research Center5, University of Edinburgh6, Paris Diderot University7, Imperial College London8, Aix-Marseille University9, Cornell University10, University of La Laguna11, Spanish National Research Council12, Complutense University of Madrid13, UK Astronomy Technology Centre14, University of Colorado Boulder15, University of California, Irvine16, Goddard Space Flight Center17, University of Nottingham18, Cardiff University19, University of Padua20, Institut d'Astrophysique de Paris21, University of Cambridge22, University of British Columbia23, European Space Research and Technology Centre24, University of Manchester25, University College London26, Rutherford Appleton Laboratory27, University of Lethbridge28, University of Oxford29, Commonwealth Scientific and Industrial Research Organisation30, University of Hertfordshire31, Harvard University32
TL;DR: The Herschel Multi-tiered Extragalactic Survey (HerMES) is a legacy program designed to map a set of nested fields totalling ~380 deg^2 as mentioned in this paper.
Abstract: The Herschel Multi-tiered Extragalactic Survey, HerMES, is a legacy program designed to map a set of nested fields totalling ~380 deg^2. Fields range in size from 0.01 to ~20 deg^2, using Herschel-SPIRE (at 250, 350 and 500 \mu m), and Herschel-PACS (at 100 and 160 \mu m), with an additional wider component of 270 deg^2 with SPIRE alone. These bands cover the peak of the redshifted thermal spectral energy distribution from interstellar dust and thus capture the re-processed optical and ultra-violet radiation from star formation that has been absorbed by dust, and are critical for forming a complete multi-wavelength understanding of galaxy formation and evolution.
The survey will detect of order 100,000 galaxies at 5\sigma in some of the best studied fields in the sky. Additionally, HerMES is closely coordinated with the PACS Evolutionary Probe survey. Making maximum use of the full spectrum of ancillary data, from radio to X-ray wavelengths, it is designed to: facilitate redshift determination; rapidly identify unusual objects; and understand the relationships between thermal emission from dust and other processes. Scientific questions HerMES will be used to answer include: the total infrared emission of galaxies; the evolution of the luminosity function; the clustering properties of dusty galaxies; and the properties of populations of galaxies which lie below the confusion limit through lensing and statistical techniques.
This paper defines the survey observations and data products, outlines the primary scientific goals of the HerMES team, and reviews some of the early results.
707 citations
TL;DR: In this article, a variety of configurations for the representation of tropospheric and stratospheric chemistry, wet removal, and online and offline meteorology are compared with surface, aircraft and satellite observations.
Abstract: . We discuss and evaluate the representation of atmospheric chemistry in the global Community Atmosphere Model (CAM) version 4, the atmospheric component of the Community Earth System Model (CESM). We present a variety of configurations for the representation of tropospheric and stratospheric chemistry, wet removal, and online and offline meteorology. Results from simulations illustrating these configurations are compared with surface, aircraft and satellite observations. Major biases include a negative bias in the high-latitude CO distribution, a positive bias in upper-tropospheric/lower-stratospheric ozone, and a positive bias in summertime surface ozone (over the United States and Europe). The tropospheric net chemical ozone production varies significantly between configurations, partly related to variations in stratosphere-troposphere exchange. Aerosol optical depth tends to be underestimated over most regions, while comparison with aerosol surface measurements over the United States indicate reasonable results for sulfate , especially in the online simulation. Other aerosol species exhibit significant biases. Overall, the model-data comparison indicates that the offline simulation driven by GEOS5 meteorological analyses provides the best simulation, possibly due in part to the increased vertical resolution (52 levels instead of 26 for online dynamics). The CAM-chem code as described in this paper, along with all the necessary datasets needed to perform the simulations described here, are available for download at www.cesm.ucar.edu .
623 citations
San Diego State University1, Harvard University2, University of California, Santa Cruz3, University of Florida4, Ames Research Center5, Villanova University6, Georgia State University7, Massachusetts Institute of Technology8, Search for extraterrestrial intelligence9, San Jose State University10, Katholieke Universiteit Leuven11, University of Texas at Austin12, University of Copenhagen13, Niels Bohr Institute14, NASA Exoplanet Science Institute15, Jet Propulsion Laboratory16, Space Telescope Science Institute17, University of California, Berkeley18, Tel Aviv University19, Las Cumbres Observatory Global Telescope Network20, University of California, Santa Barbara21, Fermilab22
TL;DR: The observed rate of circumbinary planets in this sample implies that more than ∼1% of close binary stars have giant planets in nearly coplanar orbits, yielding a Galactic population of at least several million.
Abstract: Most Sun-like stars in the Galaxy reside in gravitationally bound pairs of stars (binaries). Although long anticipated the existence of a ‘circumbinary planet’ orbiting such a pair of normal stars was not definitively established until the discovery of the planet transiting (that is, passing in front of) Kepler-16. Questions remained, however, about the prevalence of circumbinary planets and their range of orbital and physical properties. Here we report two additional transiting circumbinary planets: Kepler-34 (AB)b and Kepler-35 (AB)b, referred to here as Kepler-34 b and Kepler-35 b, respectively. Each is a low-density gas-giant planet on an orbit closely aligned with that of its parent stars. Kepler-34 b orbits two Sun-like stars every 289 days, whereas Kepler-35 b orbits a pair of smaller stars (89% and 81% of the Sun’s mass) every 131 days. The planets experience large multi-periodic variations in incident stellar radiation arising from the orbital motion of the stars. The observed rate of circumbinary planets in our sample implies that more than ~1% of close binary stars have giant planets in nearly coplanar orbits, yielding a Galactic population of at least several million.
520 citations
Goddard Space Flight Center1, Jet Propulsion Laboratory2, Centre national de la recherche scientifique3, Institut Universitaire de France4, University of Michigan5, Carnegie Institution for Science6, Georgia Institute of Technology7, Rensselaer Polytechnic Institute8, University of Hawaii9, University of Colorado Boulder10, Concordia University Wisconsin11, Cornell University12, National Autonomous University of Mexico13, Ames Research Center14, École Centrale Paris15, Honeybee Robotics16
TL;DR: The Sample Analysis at Mars (SAM) investigation of the Mars Science Laboratory (MSL) addresses the chemical and isotopic composition of the atmosphere and volatiles extracted from solid samples.
Abstract: The Sample Analysis at Mars (SAM) investigation of the Mars Science Laboratory (MSL) addresses the chemical and isotopic composition of the atmosphere and volatiles extracted from solid samples. The SAM investigation is designed to contribute substantially to the mission goal of quantitatively assessing the habitability of Mars as an essential step in the search for past or present life on Mars. SAM is a 40 kg instrument suite located in the interior of MSL’s Curiosity rover. The SAM instruments are a quadrupole mass spectrometer, a tunable laser spectrometer, and a 6-column gas chromatograph all coupled through solid and gas processing systems to provide complementary information on the same samples. The SAM suite is able to measure a suite of light isotopes and to analyze volatiles directly from the atmosphere or thermally released from solid samples. In addition to measurements of simple inorganic compounds and noble gases SAM will conduct a sensitive search for organic compounds with either thermal or chemical extraction from sieved samples delivered by the sample processing system on the Curiosity rover’s robotic arm.
475 citations
Max Planck Society1, California Institute of Technology2, Centre national de la recherche scientifique3, University of Milano-Bicocca4, University of Cambridge5, Washington University in St. Louis6, Institut de Ciències de l'Espai7, Radboud University Nijmegen8, Katholieke Universiteit Leuven9, Jet Propulsion Laboratory10, Institut d'Astrophysique de Paris11
TL;DR: The New Gravitational-Wave Observatory (NGO) as discussed by the authors, a mission under study by the European Space Agency for launch in the early 2020s, will survey the low-frequency gravitational wave sky (from 0.1 mHz to 1 Hz), detecting and characterizing a broad variety of systems and events throughout the Universe, including the coalescences of massive black holes brought together by galaxy mergers, the inspirals of stellar-mass black holes and compact stars into central galactic black holes; several millions of ultra-compact binaries, both detached and mass transferring, in
Abstract: We review the expected science performance of the New Gravitational-Wave Observatory (NGO, a.k.a. eLISA), a mission under study by the European Space Agency for launch in the early 2020s. eLISA will survey the low-frequency gravitational-wave sky (from 0.1 mHz to 1 Hz), detecting and characterizing a broad variety of systems and events throughout the Universe, including the coalescences of massive black holes brought together by galaxy mergers; the inspirals of stellar-mass black holes and compact stars into central galactic black holes; several millions of ultra-compact binaries, both detached and mass transferring, in the Galaxy; and possibly unforeseen sources such as the relic gravitational-wave radiation from the early Universe. eLISA's high signal-to-noise measurements will provide new insight into the structure and history of the Universe, and they will test general relativity in its strong-field dynamical regime.
462 citations
TL;DR: In this article, Cushing et al. presented the discovery of another seven Y dwarfs from the Wide-Field Infrared Survey Explorer (WISE) and used these objects, as well as the first six WISE Y dwarf discoveries, to explore the transition between spectral types T and Y. They found that the T/Y boundary roughly coincides with the spot where the J-H colors of brown dwarfs turn back to the red.
Abstract: We present the discovery of another seven Y dwarfs from the Wide-field Infrared Survey Explorer (WISE). Using these objects, as well as the first six WISE Y dwarf discoveries from Cushing et al., we further explore the transition between spectral types T and Y. We find that the T/Y boundary roughly coincides with the spot where the J-H colors of brown dwarfs, as predicted by models, turn back to the red. Moreover, we use preliminary trigonometric parallax measurements to show that the T/Y boundary may also correspond to the point at which the absolute H (1.6 µm) and W2 (4.6 µm) magnitudes plummet. We use these discoveries and their preliminary distances to place them in the larger context of the Solar Neighborhood. We present a table that updates the entire stellar and substellar constituency within 8 parsecs of the Sun, and we show that the current census has hydrogen-burning stars outnumbering brown dwarfs by roughly a factor of six. This factor will decrease with time as more brown dwarfs are identified within this volume, but unless there is a vast reservoir of cold brown dwarfs invisible to WISE, the final space density of brown dwarfs is still expected to fall well below that of stars. We also use these new Y dwarf discoveries, along with newly discovered T dwarfs from WISE, to investigate the field substellar mass function. We find that the overall space density of late-T and early-Y dwarfs matches that from simulations describing the mass function as a power law with slope -0.5 < α < 0.0; however, a power-law may provide a poor fit to the observed object counts as a function of spectral type because there are tantalizing hints that the number of brown dwarfs continues to rise from late-T to early-Y. More detailed monitoring and characterization of these Y dwarfs, along with dedicated searches aimed at identifying more examples, are certainly required.
411 citations
TL;DR: In this paper, the authors presented a new computationally efficient hydraulic model for simulating the spatially distributed dynamics of water surface elevation, wave speed, and inundation extent over large data sparse domains.
Abstract: [1] This paper presents a new computationally efficient hydraulic model for simulating the spatially distributed dynamics of water surface elevation, wave speed, and inundation extent over large data sparse domains. The numerical scheme is based on an extension of the hydraulic model LISFLOOD-FP to include a subgrid-scale representation of channelized flows, which allows river channels with any width below that of the grid resolution to be simulated. The scheme is shown to be numerically stable and scalable, before being applied to an 800 km reach of the river Niger in Mali. The Niger application focused on the performance of four different model structures: a model without channels (two-dimensional (2-D) model), a model without a floodplain (one-dimensional (1-D) model), a model of the main channels and floodplain (1-D/2-D model), and the subgrid approach developed here. Inclusion of both the channel network and the floodplain was shown to be essential, meaning that large scale models of this region, including routing models for land surface schemes, will require a floodplain component. Including subgrid-scale channels on the floodplain changed inundation dynamics over the delta significantly and increased simulation accuracy in terms of water level, wave propagation speed, and inundation extent. Furthermore, only the subgrid model showed a consistent parameterization when calibrated against either gauge or ICESat water level data, suggesting that connectivity provided by small channels is a strong control on the hydraulics of the floodplain, or, at the very least, that low resolution gridded hydraulic models require additional connectivity to represent the delta flow dynamics.
Netherlands Institute for Space Research1, University of Cologne2, California Institute of Technology3, Chalmers University of Technology4, Kapteyn Astronomical Institute5, École Normale Supérieure6, Centre national de la recherche scientifique7, University of Bordeaux8, Max Planck Society9, University of Toulouse10, Hoffmann-La Roche11, Spanish National Research Council12, University of Waterloo13, INAF14, Maynooth University15, Stockholm University16, ETH Zurich17, Polish Academy of Sciences18, Jet Propulsion Laboratory19, Leiden University20, Katholieke Universiteit Leuven21, University of Michigan22, University of Amsterdam23
TL;DR: In this paper, the calibration and in-orbit performance of the Heterodyne Instrument for the Far-Infrared (HIFI) is described based on a combination of ground and in flight tests.
Abstract: Aims. In this paper the calibration and in-orbit performance of the Heterodyne Instrument for the Far-Infrared (HIFI) is described. Methods. The calibration of HIFI is based on a combination of ground and in-flight tests. Dedicated ground tests to determine those instrument parameters that can only be measured accurately using controlled laboratory stimuli were carried out in the instrument level test (ILT) campaign. Special in-flight tests during the commissioning phase (CoP) and performance verification (PV) allowed the determination of the remaining instrument parameters. The various instrument observing modes, as specified in astronomical observation templates (AOTs), were validated in parallel during PV by observing selected celestial sources. Results. The initial calibration and in-orbit performance of HIFI has been established. A first estimate of the calibration budget is given. The overall in-flight instrument performance agrees with the original specification. Issues remain at only a few frequencies.
TL;DR: A revised analysis of measured changes in the net radiation imbalance at the top of the atmosphere, and the ocean heat content to a depth of 1,800m, suggests that these two sets of observations are consistent within error margins as mentioned in this paper.
Abstract: Global climate change results from a small yet persistent imbalance between the amount of sunlight absorbed by the Earth and the thermal radiation emitted back to space. A revised analysis of measured changes in the net radiation imbalance at the top of the atmosphere, and the ocean heat content to a depth of 1,800 m, suggests that these two sets of observations are consistent within error margins.
TL;DR: The Hubble Deep Field provides one of the deepest multiwavelength views of the distant Universe and has led to the detection of thousands of galaxies seen throughout cosmic time, with a redshift significantly higher than earlier estimates and higher than those of most of the hundreds of submillimetre-bright galaxies identified so far.
Abstract: The Hubble Deep Field provides one of the deepest multiwavelength views of the distant Universe and has led to the detection of thousands of galaxies seen throughout cosmic time1. An early map of the Hubble Deep Field at a wavelength of 850 micrometres, which is sensitive to dust emission powered by star formation, revealed the brightest source in the field, dubbed HDF 850.1 (ref. 2). For more than a decade, and despite significant efforts, no counterpart was found at shorter wavelengths, and it was not possible to determine its redshift, size or mass3, 4, 5, 6, 7. Here we report a redshift of z = 5.183 for HDF 850.1, from a millimetre-wave molecular line scan. This places HDF 850.1 in a galaxy overdensity at z ≈ 5.2, corresponding to a cosmic age of only 1.1 billion years after the Big Bang. This redshift is significantly higher than earlier estimates3, 4, 6, 8 and higher than those of most of the hundreds of submillimetre-bright galaxies identified so far. The source has a star-formation rate of 850 solar masses per year and is spatially resolved on scales of 5 kiloparsecs, with an implied dynamical mass of about 1.3 × 1011 solar masses, a significant fraction of which is present in the form of molecular gas. Despite our accurate determination of redshift and position, a counterpart emitting starlight remains elusive
TL;DR: CuGaTe(2) with a chalcopyrite structure demonstrates promising thermoelectric properties and the maximum figure of merit ZT is 1.4 at 950 K.
Abstract: CuGaTe_2 with a chalcopyrite structure demonstrates promising thermoelectric properties. The maximum figure of merit ZT is 1.4 at 950 K. CuGaTe_2 and related chalcopyrites are a new class of high-efficiency bulk thermoelectric material for high-temperature applications.
TL;DR: In this paper, the authors compare the data dimensionality of two contrasting scenes (a built environment at Stanford University and a lowland tropical forest in Amazonia) and demonstrate that precision data fusion greatly increases the dimensionality.
TL;DR: The Rover Environmental Monitoring Station (REMS) as discussed by the authors was designed to record air and ground temperatures, pressure, relative humidity, wind speed in the horizontal and vertical directions, as well as ultraviolet radiation in different bands.
Abstract: The Rover Environmental Monitoring Station (REMS) will investigate environmental factors directly tied to current habitability at the Martian surface during the Mars Science Laboratory (MSL) mission. Three major habitability factors are addressed by REMS: the thermal environment, ultraviolet irradiation, and water cycling. The thermal environment is determined by a mixture of processes, chief amongst these being the meteorological. Accordingly, the REMS sensors have been designed to record air and ground temperatures, pressure, relative humidity, wind speed in the horizontal and vertical directions, as well as ultraviolet radiation in different bands. These sensors are distributed over the rover in four places: two booms located on the MSL Remote Sensing Mast, the ultraviolet sensor on the rover deck, and the pressure sensor inside the rover body. Typical daily REMS observations will collect 180 minutes of data from all sensors simultaneously (arranged in 5 minute hourly samples plus 60 additional minutes taken at times to be decided during the course of the mission). REMS will add significantly to the environmental record collected by prior missions through the range of simultaneous observations including water vapor; the ability to take measurements routinely through the night; the intended minimum of one Martian year of observations; and the first measurement of surface UV irradiation. In this paper, we describe the scientific potential of REMS measurements and describe in detail the sensors that constitute REMS and the calibration procedures.
TL;DR: In this paper, the authors estimate the total rate of sea level change at selected individual islands, as a result of climate variability and change, plus vertical ground motion where available, and reconstruct a global sea level field from 1950 to 2009, combining long (over 1950-2009) good quality tide gauge records with 50-year-long gridded sea surface heights from the Ocean General Circulation Model DRAKKAR.
Paris Diderot University1, University of Paris-Sud2, Aix-Marseille University3, University of Colorado Boulder4, Ames Research Center5, University of Edinburgh6, Max Planck Society7, Jet Propulsion Laboratory8, California Institute of Technology9, University of Hawaii10, University of La Laguna11, Spanish National Research Council12, Complutense University of Madrid13, Imperial College London14, University of California, Irvine15, Cardiff University16, University of Sussex17, University of Padua18, UK Astronomy Technology Centre19, University of British Columbia20, Institut d'Astrophysique de Paris21, University College London22, University of Lethbridge23, Rutherford Appleton Laboratory24, University of Oxford25, Commonwealth Scientific and Industrial Research Organisation26, Harvard University27, University of the Western Cape28, European Space Agency29
TL;DR: In this paper, the authors derived the number counts and redshift distributions of the bright SPIRE sources in the COSMOS field with a method using the positions, the flux densities, and the redshifts of the 24 μm sources as a prior.
Abstract: Aims. The Spectral and Photometric Imaging REceiver (SPIRE) onboard the Herschel space telescope has provided confusion limited maps of deep fields at 250 μm, 350 μm, and 500 μm, as part of the Herschel Multi-tiered Extragalactic Survey (HerMES). Unfortunately, due to confusion, only a small fraction of the cosmic infrared background (CIB) can be resolved into individually-detected sources. Our goal is to produce deep galaxy number counts and redshift distributions below the confusion limit at SPIRE wavelengths (~20 mJy), which we then use to place strong constraints on the origins of the cosmic infrared background and on models of galaxy evolution.
Methods. We individually extracted the bright SPIRE sources (>20 mJy) in the COSMOS field with a method using the positions, the flux densities, and the redshifts of the 24 μm sources as a prior, and derived the number counts and redshift distributions of the bright SPIRE sources. For fainter SPIRE sources (<20 mJy), we reconstructed the number counts and the redshift distribution below the confusion limit using the deep 24 μm catalogs associated with photometric redshift and information provided by the stacking of these sources into the deep SPIRE maps of the GOODS-N and COSMOS fields. Finally, by integrating all these counts, we studied the contribution of the galaxies to the CIB as a function of their flux density and redshift.
Results. Through stacking, we managed to reconstruct the source counts per redshift slice down to ~2 mJy in the three SPIRE bands, which lies about a factor 10 below the 5σ confusion limit. Our measurements place tight constraints on source population models. None of the pre-existing models are able to reproduce our results at better than 3-σ. Finally, we extrapolate our counts to zero flux density in order to derive an estimate of the total contribution of galaxies to the CIB, finding 10.1_(-2.3)^(+2.6) nW m^(-2) sr^(-1), 6.5_(-1.6)^(+1.7) nW m^(-2) sr^(-1), and 2.8_(-0.8)^(+0.9) nW m^(-2) sr^(-1) at 250 μm, 350 μm, and 500 μm, respectively. These values agree well with FIRAS absolute measurements, suggesting our number counts and their extrapolation are sufficient to explain the CIB. We find that half of the CIB is emitted at z = 1.04, 1.20, and 1.25, respectively. Finally, combining our results with other works, we estimate the energy budget contained in the CIB between 8 μm and 1000 μm: 26_(-3)^(+7) nW m^(-2) sr^(-1).
[...]
TL;DR: Gravity data from six flybys of Saturn's moon, Titan, by the Cassini spacecraft suggest that Titan's interior is flexible on tidal time scales with the magnitude of the observed tidal deformations being consistent with the existence of a global subsurface water ocean.
Abstract: We have detected in Cassini spacecraft data the signature of the periodic tidal stresses within Titan, driven by the eccentricity (e = 0.028) of its 16-day orbit around Saturn. Precise measurements of the acceleration of Cassini during six close flybys between 2006 and 2011 have revealed that Titan responds to the variable tidal field exerted by Saturn with periodic changes of its quadrupole gravity, at about 4% of the static value. Two independent determinations of the corresponding degree-2 Love number yield k_2 = 0.589 ± 0.150 and k2 = 0.637 ± 0.224 (2σ). Such a large response to the tidal field requires that Titan’s interior be deformable over time scales of the orbital period, in a way that is consistent with a global ocean at depth.
TL;DR: In this article, a number of commonly available satellite-derived high-resolution precipitation products (HRPPs) covering northwest Europe over a 6-yr period were evaluated and compared with the European Centre for Medium-Range Weather Forecasting (ECMWF) operational forecast model products.
Abstract: Satellite-derived high-resolution precipitation products (HRPP) have been developed to address the needs of the user community and are now available with 0.25° × 0.25° (or less) subdaily resolutions. This paper evaluates a number of commonly available satellite-derived HRPPs covering northwest Europe over a 6-yr period. Precipitation products include the Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA), the Climate Prediction Center (CPC) morphing (CMORPH) technique, the CPC merged microwave technique, the Naval Research Laboratory (NRL) blended technique, and the Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN) technique. In addition, the Geosynchronous Operational Environmental Satellite (GOES) precipitation index (GPI) and the European Centre for Medium-Range Weather Forecasting (ECMWF) operational forecast model products are included for comparison. Surface reference data from the European radar network...
TL;DR: In this paper, the authors present the results of a mid-infrared survey of 11 outer Galaxy massive star-forming regions and 3 open clusters with data from the Wide-field Infrared Survey Explorer (WISE).
Abstract: We present the results of a mid-infrared survey of 11 outer Galaxy massive star-forming regions and 3 open clusters with data from the Wide-field Infrared Survey Explorer (WISE). Using a newly developed photometric scheme to identify young stellar objects and exclude extragalactic contamination, we have studied the distribution of young stars within each region. These data tend to support the hypothesis that latter generations may be triggered by the interaction of winds and radiation from the first burst of massive star formation with the molecular cloud material leftover from that earlier generation of stars. We dub this process the "fireworks hypothesis" since star formation by this mechanism would proceed rapidly and resemble a burst of fireworks. We have also analyzed small cutout WISE images of the structures around the edges of these massive star-forming regions. We observe large (1-3 pc size) pillar and trunk-like structures of diffuse emission nebulosity tracing excited polycyclic aromatic hydrocarbon molecules and small dust grains at the perimeter of the massive star-forming regions. These structures contain small clusters of emerging Class I and Class II sources, but some are forming only a single to a few new stars.
University of Hawaii1, Max Planck Society2, University of Paris-Sud3, Paris Diderot University4, Jet Propulsion Laboratory5, California Institute of Technology6, University of Massachusetts Amherst7, Centre national de la recherche scientifique8, University of British Columbia9, European Space Agency10, Dalhousie University11, University of Cambridge12, Imperial College London13, University of Colorado Boulder14, University of Nottingham15, University of California, Irvine16, Virginia Tech17, UK Astronomy Technology Centre18, University of Edinburgh19, University of Oxford20, University of Sussex21, University College London22, Rutherford Appleton Laboratory23, Commonwealth Scientific and Industrial Research Organisation24
TL;DR: In this article, Keck spectroscopic observations and redshifts for a sample of 767 Herschel-SPIRE selected galaxies (HSGs) at 250, 350, and 500 μm were taken with the Keck I Low Resolution Imaging Spectrometer and the KECK II DEep Imaging Multi-Object Spectrograph.
Abstract: We present Keck spectroscopic observations and redshifts for a sample of 767 Herschel-SPIRE selected galaxies (HSGs) at 250, 350, and 500 μm, taken with the Keck I Low Resolution Imaging Spectrometer and the Keck II DEep Imaging Multi-Object Spectrograph. The redshift distribution of these SPIRE sources from the Herschel Multitiered Extragalactic Survey peaks at z = 0.85, with 731 sources at z < 2 and a tail of sources out to z ~ 5. We measure more significant disagreement between photometric and spectroscopic redshifts (〈Δz/(1 + z_(spec))〉 = 0.29) than is seen in non-infrared selected samples, likely due to enhanced star formation rates and dust obscuration in infrared-selected galaxies. The infrared data are used to directly measure integrated infrared luminosities and dust temperatures independent of radio or 24 μm flux densities. By probing the dust spectral energy distribution (SED) at its peak, we estimate that the vast majority (72%-83%) of z < 2 Herschel-selected galaxies would drop out of traditional submillimeter surveys at 0.85-1 mm. We find that dust temperature traces infrared luminosity, due in part to the SPIRE wavelength selection biases, and partially from physical effects. As a result, we measure no significant trend in SPIRE color with redshift; if dust temperature were independent of luminosity or redshift, a trend in SPIRE color would be expected. Composite infrared SEDs are constructed as a function of infrared luminosity, showing the increase in dust temperature with luminosity, and subtle change in near-infrared and mid-infrared spectral properties. Moderate evolution in the far-infrared (FIR)/radio correlation is measured for this partially radio-selected sample, with q_(IR) ∝(1 + z)^(–0.30±0.02) at z < 2. We estimate the luminosity function and implied star formation rate density contribution of HSGs at z < 1.6 and find overall agreement with work based on 24 μm extrapolations of the LIRG, ULIRG, and total infrared contributions. This work significantly increased the number of spectroscopically confirmed infrared-luminous galaxies at z » 0 and demonstrates the growing importance of dusty starbursts for galaxy evolution studies and the build-up of stellar mass throughout cosmic time.
TL;DR: Dawn’s global mapping of Vesta reveals that its observed south polar depression is composed of two overlapping giant impact features, which provide exceptional windows into impact processes at planetary scales, and spacecraft data provide a detailed characterization of the second most massive asteroid in the solar system.
Abstract: Since 17 July 2011, NASA's spacecraft Dawn has been orbiting the asteroid Vesta—the second most massive and the third largest asteroid in the solar system (see the cover). Russell et al. (p. [684][1]) use Dawn's observations to confirm that Vesta is a small differentiated planetary body with an inner core, and represents a surviving proto-planet from the earliest epoch of solar system formation; Vesta is also confirmed as the source of the howardite-eucrite-diogenite (HED) meteorites. Jaumann et al. (p. [687][2]) report on the asteroid's overall geometry and topography, based on global surface mapping. Vesta's surface is dominated by numerous impact craters and large troughs around the equatorial region. Marchi et al. (p. [690][3]) report on Vesta's complex cratering history and constrain the age of some of its major regions based on crater counts. Schenk et al. (p. [694][4]) describe two giant impact basins located at the asteroid's south pole. Both basins are young and excavated enough amounts of material to form the Vestoids—a group of asteroids with a composition similar to that of Vesta—and HED meteorites. De Sanctis et al. (p. [697][5]) present the mineralogical characterization of Vesta, based on data obtained by Dawn's visual and infrared spectrometer, revealing that this asteroid underwent a complex magmatic evolution that led to a differentiated crust and mantle. The global color variations detailed by Reddy et al. (p. [700][6]) are unlike those of any other asteroid observed so far and are also indicative of a preserved, differentiated proto-planet.
[1]: /lookup/doi/10.1126/science.1219381
[2]: /lookup/doi/10.1126/science.1219122
[3]: /lookup/doi/10.1126/science.1218757
[4]: /lookup/doi/10.1126/science.1223272
[5]: /lookup/doi/10.1126/science.1219270
[6]: /lookup/doi/10.1126/science.1219088
TL;DR: The Radiation Assessment Detector (RAD) on the Mars Science Laboratory (MSL) is an energetic particle detector designed to measure a broad spectrum of energetic particle radiation as mentioned in this paper.
Abstract: The Radiation Assessment Detector (RAD) on the Mars Science Laboratory (MSL) is an energetic particle detector designed to measure a broad spectrum of energetic particle radiation. It will make the first-ever direct radiation measurements on the surface of Mars, detecting galactic cosmic rays, solar energetic particles, secondary neutrons, and other secondary particles created both in the atmosphere and in the Martian regolith. The radiation environment on Mars, both past and present, may have implications for habitability and the ability to sustain life. Radiation exposure is also a major concern for future human missions. The RAD instrument combines charged- and neutral-particle detection capability over a wide dynamic range in a compact, low-mass, low-power instrument. These capabilities are required in order to measure all the important components of the radiation environment. RAD consists of the RAD Sensor Head (RSH) and the RAD Electronics Box (REB) integrated together in a small, compact volume. The RSH contains a solid-state detector telescope with three silicon PIN diodes for charged particle detection, a thallium doped Cesium Iodide scintillator, plastic scintillators for neutron detection and anti-coincidence shielding, and the front-end electronics. The REB contains three circuit boards, one with a novel mixed-signal ASIC for processing analog signals and an associated control FPGA, another with a second FPGA to communicate with the rover and perform onboard analysis of science data, and a third board with power supplies and power cycling or “sleep”-control electronics. The latter enables autonomous operation, independent of commands from the rover. RAD is a highly capable and highly configurable instrument that paves the way for future compact energetic particle detectors in space.
TL;DR: In this article, the authors show that WISE colors alone are effective in isolating stars (or local early-type galaxies), star-forming galaxies and strong AGN/QSOs at z 0.9+-0.5mJy.
Abstract: The Wide-field Infrared Survey Explorer (WISE) has completed its all-sky survey at 3.4-22 micron. We merge the WISE data with optical SDSS data and provide a phenomenological characterization of mid-IR, extragalactic sources. WISE is most sensitive at 3.4micron(W1) and least at 22micron(W4). The W1 band probes massive early-type galaxies out to z\gtrsim1. This is more distant than SDSS identified early-type galaxies, consistent with the fact that 28% of 3.4micron sources have faint or no r-band counterparts (r>22.2). In contrast, 92-95% of 12 and 22micron sources have SDSS optical counterparts with r 7, but only 18.9% at 22micron with SNR(W4)>5. We show that WISE colors alone are effective in isolating stars (or local early-type galaxies), star-forming galaxies and strong AGN/QSOs at z 0.8 and W2 0.8, W2 6 (Vega) colors can be used to identify type-2 AGN candidates. The fraction of these type-2 AGN candidates is 1/3rd of all WISE color-selected AGNs. (3) Selection of ULIRGs at z\sim2 with extremely red colors, r-W4>14 or well-detected 22micron sources lacking detections in the 3.4 and 4.6micron bands. The surface density of z~2 r-W4>14 ULIRGs is 0.9+-0.07/deg^2 at SNR(W4)>5 (flux(W4)>=2.5mJy), which is consistent with that inferred from smaller area Spitzer surveys. Optical spectroscopy of a small number of these high-redshift ULIRGs confirms our selection, and reveals a possible trend that optically fainter or r-W4 redder candidates are at higher redshifts.
TL;DR: The atomic C II fine-structure line is one of the brightest lines in a typical star-forming galaxy spectrum with a luminosity ~ 1% of the bolometric luminosity as discussed by the authors.
Abstract: The atomic C II fine-structure line is one of the brightest lines in a typical star-forming galaxy spectrum with a luminosity ~01%-1% of the bolometric luminosity It is potentially a reliable tracer of the dense gas distribution at high redshifts and could provide an additional probe to the era of reionization By taking into account the spontaneous, stimulated, and collisional emission of the C II line, we calculate the spin temperature and the mean intensity as a function of the redshift When averaged over a cosmologically large volume, we find that the C II emission from ionized carbon in individual galaxies is larger than the signal generated by carbon in the intergalactic medium Assuming that the C II luminosity is proportional to the carbon mass in dark matter halos, we also compute the power spectrum of the C II line intensity at various redshifts In order to avoid the contamination from CO rotational lines at low redshift when targeting a C II survey at high redshifts, we propose the cross-correlation of C II and 21 cm line emission from high redshifts To explore the detectability of the C II signal from reionization, we also evaluate the expected errors on the C II power spectrum and C II-21 cm cross power spectrum based on the design of the future millimeter surveys We note that the C II-21 cm cross power spectrum contains interesting features that capture physics during reionization, including the ionized bubble sizes and the mean ionization fraction, which are challenging to measure from 21 cm data alone We propose an instrumental concept for the reionization C II experiment targeting the frequency range of ~200-300 GHz with 1, 3, and 10 m apertures and a bolometric spectrometer array with 64 independent spectral pixels with about 20,000 bolometers
TL;DR: In this article, a ring fiber with 0.05 up-doping is designed in simulation to support up to 10 OAM modes while maintaining single-mode condition radially, and the mode index difference can be maintained above 10-4 over hundreds of nanometers optical bandwidth.
Abstract: We simulate and analyze the mode properties and propagation effects of orbital angular momentum (OAM) modes in a ring fiber. A ring fiber with 0.05 up-doping is designed in simulation to support up to 10 OAM modes while maintaining single-mode condition radially. With a multiple-ring fiber, tens of OAM modes can be potentially multiplexed to greatly enhance the system capacity and spectral efficiency. The mode index difference can be maintained above 10-4 over hundreds of nanometers optical bandwidth. Higher order OAM modes' azimuthal intensity and odd-order OAM modes' azimuthal phase show better tolerance to the fiber ellipticity. Moreover, higher order OAM modes also have longer 2π and 10-ps walk-off length. After 600-km propagation, OAM0,4 mode shows <; 10-ps mode walk- off, even in a ring fiber with 1% ellipticity. Also, in such an elliptical fiber, the well-aligned OAM modes with different charges have <;-20 dB intermode crosstalk. The improvement of the circularity for the ring fiber is expected to reduce the crosstalk and increase the demultiplexing efficiency.
Posted Content•
TL;DR: In this paper, the authors present six Impact Challenges to explicitly focus the field's energy and attention on problems of import to the larger world of science and society, and discuss existing obstacles that must be addressed.
Abstract: Much of current machine learning (ML) research has lost its connection to problems of import to the larger world of science and society. From this perspective, there exist glaring limitations in the data sets we investigate, the metrics we employ for evaluation, and the degree to which results are communicated back to their originating domains. What changes are needed to how we conduct research to increase the impact that ML has? We present six Impact Challenges to explicitly focus the field?s energy and attention, and we discuss existing obstacles that must be addressed. We aim to inspire ongoing discussion and focus on ML that matters.
[...]
01 Dec 2012
TL;DR: The signature of the periodic tidal stresses within Titan, driven by the eccentricity (e = 0.028) of its 16-day orbit around Saturn, was detected in Cassini spacecraft data.
Abstract: We have detected in Cassini spacecraft data the signature of the periodic tidal stresses within Titan, driven by the eccentricity (e = 0.028) of its 16-day orbit around Saturn. Precise measurements of the acceleration of Cassini during six close flybys between 2006 and 2011 have revealed that Titan responds to the variable tidal field exerted by Saturn with periodic changes of its quadrupole gravity, at about 4% of the static value. Two independent determinations of the corresponding degree-2 Love number yield k_2 = 0.589 ± 0.150 and k2 = 0.637 ± 0.224 (2σ). Such a large response to the tidal field requires that Titan’s interior be deformable over time scales of the orbital period, in a way that is consistent with a global ocean at depth.