What about the messenger
01 Dec 2006-Vol. 2006, Iss: 4, pp 18-19
TL;DR: In this article, NAFU SA and other role players expressed some criticism about government programmes. The criticism was not so much about the objectives and content of these programmes, but rather about their accessibility, or lack thereof, to emerging farmers.
Abstract: Recently NAFU SA and other role players expressed some criticism about government programmes. The criticism was not so much about the objectives and content of these programmes, but rather about their accessibility, or lack thereof, to emerging farmers.
Citations
More filters
Max Planck Society1, McGill University2, University of Toronto3, University of Manchester4, University of Sheffield5, German Aerospace Center6, University of Amsterdam7, ASTRON8, Lebedev Physical Institute9, University of Warwick10, West Virginia University11, University of Virginia12, National Radio Astronomy Observatory13, University of British Columbia14
TL;DR: Pulsar J0348+0432 is only the second neutron star with a precisely determined mass of 2 M☉
Abstract: Many physically motivated extensions to general relativity (GR) predict significant deviations at energies present in massive neutron stars. We report the measurement of a 2.01 \(\pm \) 0.04 solar mass (M\(_\odot \)) pulsar in a 2.46-h orbit around a 0.172 \(\pm \) 0.003 M\(_\odot \) white dwarf. The high pulsar mass and the compact orbit make this system a sensitive laboratory of a previously untested strong-field gravity regime. Thus far, the observed orbital decay agrees with GR, supporting its validity even for the extreme conditions present in the system. The resulting constraints on deviations support the use of GR-based templates for ground-based gravitational wave detection experiments. Additionally, the system strengthens recent constraints on the properties of dense matter and provides novel insight to binary stellar astrophysics and pulsar recycling.
3,224 citations
University of California, Santa Cruz1, University of Arizona2, University of Oxford3, Lawrence Berkeley National Laboratory4, Seoul National University5, University of California, Berkeley6, Princeton University7, University of Texas at Austin8, Max Planck Society9, University of Chicago10, National Taiwan University11, University of Florida12, University of Virginia13, Herzberg Institute of Astrophysics14, Johns Hopkins University15, New Mexico State University16
TL;DR: The DEEP2 and COMBO-17 surveys are compared to study luminosity functions of red and blue galaxies to z ~ 1, and the results imply that the number and total stellar mass of blue galaxies have been substantially constant since z = 1, whereas those of red galaxies (near L*) have been significantly rising as mentioned in this paper.
Abstract: The DEEP2 and COMBO-17 surveys are compared to study luminosity functions of red and blue galaxies to z ~ 1. The two surveys have different methods and sensitivities, but nevertheless results agree. After z ~ 1, M has dimmed by 1.2-1.3 mag for all colors of galaxies, * for blue galaxies has hardly changed, and * for red galaxies has at least doubled (our formal value is ~0.5 dex). Luminosity density jB has fallen by 0.6 dex for blue galaxies but has remained nearly constant for red galaxies. These results imply that the number and total stellar mass of blue galaxies have been substantially constant since z ~ 1, whereas those of red galaxies (near L*) have been significantly rising. To explain the new red galaxies, a ``mixed'' scenario is proposed in which star formation in blue cloud galaxies is quenched, causing them to migrate to the red sequence, where they merge further in a small number of stellar mergers. This mixed scenario matches the local boxy-disky transition for nearby ellipticals, as well as red sequence stellar population scaling laws such as the color-magnitude and Mg-? relations (which are explained as fossil relics from blue progenitors). Blue galaxies enter the red sequence via different quenching modes, each of which peaks at a different characteristic mass and time. The red sequence therefore likely builds up in different ways at different times and masses, and the concept of a single process that is ``downsizing'' (or upsizing) probably does not apply. Our claim in this paper of a rise in the number of red galaxies applies to galaxies near L*. Accurate counts of brighter galaxies on the steep part of the Schechter function require more accurate photometry than is currently available.
1,193 citations
TL;DR: A review of the results of quantitative studies in nearby dwarf galaxies can be found in this paper, where the combination of spectroscopy and imaging and what they have taught us about dwarf galaxy formation and evolution is the aim of this work.
Abstract: Within the Local Universe galaxies can be studied in great detail star by star, and here we review the results of quantitative studies in nearby dwarf galaxies. The color-magnitude diagram synthesis method is well established as the most accurate way to determine star-formation histories of galaxies back to the earliest times. This approach received a large boost from the exceptional data sets that wide-field CCD imagers on the ground and the Hubble Space Telescope could provide. Spectroscopic studies using large ground-based telescopes such as VLT, Magellan, Keck, and HET have allowed the determination of abundances and kinematics for significant samples of stars in nearby dwarf galaxies. These studies have shown how the properties of stellar populations can vary spatially and temporally. This leads to important constraints to theories of galaxy formation and evolution. The combination of spectroscopy and imaging and what they have taught us about dwarf galaxy formation and evolution is the aim of this r...
1,165 citations
Curtin University1, Massachusetts Institute of Technology2, Arizona State University3, University of Washington4, University of Western Australia5, Monash University6, Harvard University7, Commonwealth Scientific and Industrial Research Organisation8, Raman Research Institute9, Victoria University of Wellington10, University of Wisconsin–Milwaukee11, National Centre for Radio Astrophysics12, National Radio Astronomy Observatory13, University of Melbourne14
TL;DR: The Murchison Widefield Array (MWA) as discussed by the authors is one of three Square Kilometre Array Precursor telescopes and is located at the MUR-astronomy Observatory in Western Australia, a location chosen for its extremely low levels of radio frequency interference.
Abstract: The Murchison Widefield Array (MWA) is one of three Square Kilometre Array Precursor telescopes and is located at the Murchison Radio-astronomy Observatory in the Murchison Shire of the mid-west of Western Australia, a location chosen for its extremely low levels of radio frequency interference. The MWA operates at low radio frequencies, 80-300 MHz, with a processed bandwidth of 30.72 MHz for both linear polarisations, and consists of 128 aperture arrays (known as tiles) distributed over a ∼3-km diameter area. Novel hybrid hardware/software correlation and a real-time imaging and calibration systems comprise the MWA signal processing backend. In this paper, the as-built MWA is described both at a system and sub-system level, the expected performance of the array is presented, and the science goals of the instrument are summarised. © 2013 Astronomical Society of Australia.
1,144 citations
Cites methods from "What about the messenger"
...The MWA data archive will utilise the ngas software (Wicenec & Knudstrup 2007) and is implemented on a single server machine....
[...]
Harvard University1, Fermilab2, Stanford University3, University of California, Berkeley4, Johns Hopkins University5, Space Telescope Science Institute6, University of Notre Dame7, University of Washington8, Australian National University9, Pontifical Catholic University of Chile10, University of Toronto11, University of Copenhagen12, Texas A&M University13, European Southern Observatory14, Ohio State University15, Stockholm University16, University of Hawaii17
TL;DR: In this paper, a set of constraints on the dark energy equation-of-state parameter w = P/(rho c(2)) were derived using 60 SNe Ia from the ESSENCE supernova survey.
Abstract: We present constraints on the dark energy equation-of-state parameter, w = P/(rho c(2)), using 60 SNe Ia fromthe ESSENCE supernova survey. We derive a set of constraints on the nature of the dark energy assuming a flat universe. By including constraints on (Omega(M), w) from baryon acoustic oscillations, we obtain a value for a static equation-of-state parameter w = -1:05(-0.12)(+0: 13) (stat 1 sigma) +/- 0: 13 (sys) and Omega(M) = 0:274(-0.020)(+0:033) (stat 1 sigma) with a bestfit chi(2)/dof of 0.96. These results are consistent with those reported by the Supernova Legacy Survey from the first year of a similar program measuring supernova distances and redshifts. We evaluate sources of systematic error that afflict supernova observations and present Monte Carlo simulations that explore these effects. Currently, the largest systematic with the potential to affect our measurements is the treatment of extinction due to dust in the supernova host galaxies. Combining our set of ESSENCE SNe Ia with the first-results Supernova Legacy Survey SNe Ia, we obtain a joint constraint of w = -1:07(-0: 09)(+0:09) (stat 1 sigma) +/- 0: 13 ( sys), Omega(M) 0:267(-0:028)(+0:028) (stat 1 sigma) with a best-fit chi(2)/dof of 0.91. The current global SN Ia data alone rule out empty (Omega(M) = 0), matter-only Omega(M) = 0: 3, and Omega(M) = 1 universes at > 4.5 sigma. The current SN Ia data are fully consistent with a cosmological constant.
989 citations
References
More filters
Max Planck Society1, McGill University2, University of Toronto3, University of Manchester4, University of Sheffield5, German Aerospace Center6, University of Amsterdam7, ASTRON8, Lebedev Physical Institute9, University of Warwick10, West Virginia University11, University of Virginia12, National Radio Astronomy Observatory13, University of British Columbia14
TL;DR: Pulsar J0348+0432 is only the second neutron star with a precisely determined mass of 2 M☉
Abstract: Many physically motivated extensions to general relativity (GR) predict significant deviations at energies present in massive neutron stars. We report the measurement of a 2.01 \(\pm \) 0.04 solar mass (M\(_\odot \)) pulsar in a 2.46-h orbit around a 0.172 \(\pm \) 0.003 M\(_\odot \) white dwarf. The high pulsar mass and the compact orbit make this system a sensitive laboratory of a previously untested strong-field gravity regime. Thus far, the observed orbital decay agrees with GR, supporting its validity even for the extreme conditions present in the system. The resulting constraints on deviations support the use of GR-based templates for ground-based gravitational wave detection experiments. Additionally, the system strengthens recent constraints on the properties of dense matter and provides novel insight to binary stellar astrophysics and pulsar recycling.
3,224 citations
University of California, Santa Cruz1, University of Arizona2, University of Oxford3, Lawrence Berkeley National Laboratory4, Seoul National University5, University of California, Berkeley6, Princeton University7, University of Texas at Austin8, Max Planck Society9, University of Chicago10, National Taiwan University11, University of Florida12, University of Virginia13, Herzberg Institute of Astrophysics14, Johns Hopkins University15, New Mexico State University16
TL;DR: The DEEP2 and COMBO-17 surveys are compared to study luminosity functions of red and blue galaxies to z ~ 1, and the results imply that the number and total stellar mass of blue galaxies have been substantially constant since z = 1, whereas those of red galaxies (near L*) have been significantly rising as mentioned in this paper.
Abstract: The DEEP2 and COMBO-17 surveys are compared to study luminosity functions of red and blue galaxies to z ~ 1. The two surveys have different methods and sensitivities, but nevertheless results agree. After z ~ 1, M has dimmed by 1.2-1.3 mag for all colors of galaxies, * for blue galaxies has hardly changed, and * for red galaxies has at least doubled (our formal value is ~0.5 dex). Luminosity density jB has fallen by 0.6 dex for blue galaxies but has remained nearly constant for red galaxies. These results imply that the number and total stellar mass of blue galaxies have been substantially constant since z ~ 1, whereas those of red galaxies (near L*) have been significantly rising. To explain the new red galaxies, a ``mixed'' scenario is proposed in which star formation in blue cloud galaxies is quenched, causing them to migrate to the red sequence, where they merge further in a small number of stellar mergers. This mixed scenario matches the local boxy-disky transition for nearby ellipticals, as well as red sequence stellar population scaling laws such as the color-magnitude and Mg-? relations (which are explained as fossil relics from blue progenitors). Blue galaxies enter the red sequence via different quenching modes, each of which peaks at a different characteristic mass and time. The red sequence therefore likely builds up in different ways at different times and masses, and the concept of a single process that is ``downsizing'' (or upsizing) probably does not apply. Our claim in this paper of a rise in the number of red galaxies applies to galaxies near L*. Accurate counts of brighter galaxies on the steep part of the Schechter function require more accurate photometry than is currently available.
1,193 citations
Curtin University1, Massachusetts Institute of Technology2, Arizona State University3, University of Washington4, University of Western Australia5, Monash University6, Harvard University7, Commonwealth Scientific and Industrial Research Organisation8, Raman Research Institute9, Victoria University of Wellington10, University of Wisconsin–Milwaukee11, National Centre for Radio Astrophysics12, National Radio Astronomy Observatory13, University of Melbourne14
TL;DR: The Murchison Widefield Array (MWA) as discussed by the authors is one of three Square Kilometre Array Precursor telescopes and is located at the MUR-astronomy Observatory in Western Australia, a location chosen for its extremely low levels of radio frequency interference.
Abstract: The Murchison Widefield Array (MWA) is one of three Square Kilometre Array Precursor telescopes and is located at the Murchison Radio-astronomy Observatory in the Murchison Shire of the mid-west of Western Australia, a location chosen for its extremely low levels of radio frequency interference. The MWA operates at low radio frequencies, 80-300 MHz, with a processed bandwidth of 30.72 MHz for both linear polarisations, and consists of 128 aperture arrays (known as tiles) distributed over a ∼3-km diameter area. Novel hybrid hardware/software correlation and a real-time imaging and calibration systems comprise the MWA signal processing backend. In this paper, the as-built MWA is described both at a system and sub-system level, the expected performance of the array is presented, and the science goals of the instrument are summarised. © 2013 Astronomical Society of Australia.
1,144 citations
TL;DR: In this article, a set of constraints on the dark energy equation-of-state parameter w =P/(rho c^2) were derived for 60 Type Ia supernovae from the ESSENCE supernova survey.
Abstract: We present constraints on the dark energy equation-of-state parameter, w=P/(rho c^2), using 60 Type Ia supernovae (SNe Ia) from the ESSENCE supernova survey. We derive a set of constraints on the nature of the dark energy assuming a flat Universe. By including constraints on (Omega_M, w) from baryon acoustic oscillations, we obtain a value for a static equation-of-state parameter w=-1.05^{+0.13}_{-0.12} (stat; 1 sigma) +- 0.11 (sys) and Omega_M=0.274^{+0.033}_{-0.020} (stat; 1 sigma) with a best-fit chi^2/DoF of 0.96. These results are consistent with those reported by the SuperNova Legacy Survey in a similar program measuring supernova distances and redshifts. We evaluate sources of systematic error that afflict supernova observations and present Monte Carlo simulations that explore these effects. Currently, the largest systematic currently with the potential to affect our measurements is the treatment of extinction due to dust in the supernova host galaxies. Combining our set of ESSENCE SNe Ia with the SuperNova Legacy Survey SNe Ia, we obtain a joint constraint of w=-1.07^{+0.09}_{-0.09} (stat; 1 sigma) +- 0.12 (sys), Omega_M=0.267^{+0.028}_{-0.018} (stat; 1 sigma) with a best-fit chi^2/DoF of 0.91. The current SN Ia data are fully consistent with a cosmological constant.
863 citations
Australia Telescope National Facility1, Swinburne University of Technology2, Universidad de Guanajuato3, University of Melbourne4, Mount Stromlo Observatory5, University of New Mexico6, University of Colorado Boulder7, European Southern Observatory8, Cardiff University9, University of Western Sydney10, University of Queensland11, University of Sydney12, ASTRON13, University of Leicester14
TL;DR: The HIPASS Bright Galaxy Catalog (BGC) as mentioned in this paper contains 1000 H I brightest galaxies in the southern sky as obtained from the H i Parkes All-Sky Survey ( HIPASS).
Abstract: We present the HIPASS Bright Galaxy Catalog (BGC), which contains the 1000 H I brightest galaxies in the southern sky as obtained from the H i Parkes All-Sky Survey ( HIPASS). The selection of the brightest sources is based on their H I peak flux density (S-peak greater than or similar to116 mJy) as measured from the spatially integrated HIPASS spectrum. The derived H I masses range from similar to10(7) to 4 x 10(10) M-.. While the BGC ( z 10degrees. Therefore, the BGC yields no evidence for a population of free-floating'' intergalactic H I clouds without associated optical counterparts. HIPASS provides a clear view of the local large-scale structure. The dominant features in the sky distribution of the BGC are the Supergalactic Plane and the Local Void. In addition, one can clearly see the Centaurus Wall, which connects via the Hydra and Antlia Clusters to the Puppis Filament. Some previously hardly noticable galaxy groups stand out quite distinctly in the H I sky distribution. Several new structures, including some not behind the Milky Way, are seen for the first time.
513 citations