Abstract
We present measurements of the weak gravitational lensing shear power spectrum based on
$450 \deg ^2$
of imaging data from the Kilo Degree Survey. We employ a quadratic estimator in two and ...three redshift bins and extract band powers of redshift autocorrelation and cross-correlation spectra in the multipole range 76 ≤ ℓ ≤ 1310. The cosmological interpretation of the measured shear power spectra is performed in a Bayesian framework assuming a ΛCDM model with spatially flat geometry, while accounting for small residual uncertainties in the shear calibration and redshift distributions as well as marginalizing over intrinsic alignments, baryon feedback and an excess-noise power model. Moreover, massive neutrinos are included in the modelling. The cosmological main result is expressed in terms of the parameter combination
$S_8 \equiv \sigma _8 \sqrt{\Omega _{\rm m}/0.3}$
yielding S
8 = 0.651 ± 0.058 (three z-bins), confirming the recently reported tension in this parameter with constraints from Planck at 3.2σ (three z-bins). We cross-check the results of the three z-bin analysis with the weaker constraints from the two z-bin analysis and find them to be consistent. The high-level data products of this analysis, such as the band power measurements, covariance matrices, redshift distributions and likelihood evaluation chains are available at http://kids.strw.leidenuniv.nl.
We present cosmological parameter constraints from a tomographic weak gravitational lensing analysis of ~450 deg super( 2) of imaging data from the Kilo Degree Survey (KiDS). For a flat ... cold dark ...matter (...CDM) cosmology with a prior on H sub( 0) that encompasses the most recent direct measurements, we find S sub( 8) ... = 0.745 plus or minus 0.039. This result is in good agreement with other low-redshift probes of large-scale structure, including recent cosmic shear results, along with pre-Planck cosmic microwave background constraints. A 2.3... tension in S sub( 8) and 'substantial discordance' in the full parameter space is found with respect to the Planck 2015 results. We use shear measurements for nearly 15 million galaxies, determined with a new improved 'self-calibrating' version of lensfit validated using an extensive suite of image simulations. Four-band ugri photometric redshifts are calibrated directly with deep spectroscopic surveys. The redshift calibration is confirmed using two independent techniques based on angular cross-correlations and the properties of the photometric redshift probability distributions. Our covariance matrix is determined using an analytical approach, verified numerically with large mock galaxy catalogues. We account for uncertainties in the modelling of intrinsic galaxy alignments and the impact of baryon feedback on the shape of the non-linear matter power spectrum, in addition to the small residual uncertainties in the shear and redshift calibration. The cosmology analysis was performed blind. Our high-level data products, including shear correlation functions, covariance matrices, redshift distributions, and Monte Carlo Markov chains are available at http://kids.strw.leidenuniv.nl. (ProQuest: ... denotes formulae/symbols omitted.)
We present a new training set for estimating empirical photometric redshifts of galaxies, which was created as part of the 2-degree Field Lensing Survey project. This training set is located in a ...~700 deg super( 2) area of the Kilo-Degree-Survey South field and is randomly selected and nearly complete at r < 19.5. We investigate the photometric redshift performance obtained with ugriz photometry from VST-ATLAS and W1/W2 from WISE, based on several empirical and template methods. The best redshift errors are obtained with kernel-density estimation (KDE), as are the lowest biases, which are consistent with zero within statistical noise. The 68th percentiles of the redshift scatter for magnitude-limited samples at r < (15.5, 17.5, 19.5) are (0.014, 0.017, 0.028). In this magnitude range, there are no known ambiguities in the colour-redshift map, consistent with a small rate of redshift outliers. In the fainter regime, the KDE method produces p(z) estimates per galaxy that represent unbiased and accurate redshift frequency expectations. The p(z) sum over any subsample is consistent with the true redshift frequency plus Poisson noise. Further improvements in redshift precision at r < 20 would mostly be expected from filter sets with narrower passbands to increase the sensitivity of colours to small changes in redshift.
Abstract
We present a weak gravitational lensing analysis of 815 deg2 of i-band imaging from the Kilo-Degree Survey (KiDS-i-800). In contrast to the deep r-band observations, which take priority ...during excellent seeing conditions and form the primary KiDS data set (KiDS‐r‐450), the complementary yet shallower KiDS-i-800 spans a wide range of observing conditions. The overlapping KiDS-i-800 and KiDS‐r‐450 imaging therefore provides a unique opportunity to assess the robustness of weak lensing measurements. In our analysis we introduce two new ‘null’ tests. The ‘nulled’ two-point shear correlation function uses a matched catalogue to show that the calibrated KiDS-i-800 and KiDS‐r‐450 shear measurements agree at the level of 1 ± 4 per cent. We use five galaxy lens samples to determine a ‘nulled’ galaxy–galaxy lensing signal from the full KiDS-i-800 and KiDS‐r‐450 surveys and find that the measurements agree to 7 ± 5 per cent when the KiDS-i-800 source redshift distribution is calibrated using either spectroscopic redshifts, or the 30-band photometric redshifts from the COSMOS survey.
The Global Ozone Monitoring Experiment-2 (GOME-2) flies on the Metop series of satellites, the space component of the EUMETSAT Polar System. In this paper we will provide an overview of the ...instrument design, the on-ground calibration and characterization activities, in-flight calibration, and level 0 to 1 data processing. The current status of the level 1 data is presented and points of specific relevance to users are highlighted. Long-term level 1 data consistency is also discussed and plans for future work are outlined. The information contained in this paper summarizes a large number of technical reports and related documents containing information that is not currently available in the published literature. These reports and documents are however made available on the EUMETSAT web pages and readers requiring more details than can be provided in this overview paper will find appropriate references at relevant points in the text.
We report follow-up observations of 477 program Near-Earth Asteroids (NEAs) using nine telescopes of the EURONEAR network having apertures between 0.3 and 4.2m. Adding these NEAs to our previous ...results we now count 739 program NEAs followed-up by the EURONEAR network since 2006. The targets were selected using EURONEAR planning tools focusing on high priority objects. Analyzing the resulting orbital improvements suggests astrometric follow-up is most important days to weeks after discovery, with recovery at a new opposition also valuable. Additionally we observed 40 survey fields spanning three nights covering 11 square degrees near opposition, using the Wide Field Camera on the 2.5m Isaac Newton Telescope (INT), resulting in 104 discovered main belt asteroids (MBAs) and another 626 unknown one-night objects. These fields, plus program NEA fields from the INT and from the wide field MOSAIC II camera on the Blanco 4m telescope, generated around 12000 observations of 2000 minor planets (mostly MBAs) observed in 34 square degrees. We identify Near Earth Object (NEO) candidates among the unknown (single night) objects using three selection criteria. Testing these criteria on the (known) program NEAs shows that the best selection method is our ϵ−μ model which checks solar elongation and sky motion and the MPC's NEO rating tool. Our new data show that on average 0.5 NEO candidates per square degree should be observable in a 2m-class survey (in agreement with past results), while an average of 2.7 NEO candidates per square degree should be observable in a 4m-class survey (although our Blanco statistics were affected by clouds). At opposition just over 100 MBAs (1.6 unknown to every 1 known) per square degree are detectable to R=22 in a 2m survey based on the INT data (in accordance with other results), while our two best ecliptic Blanco fields away from opposition lead to 135 MBAs (2 unknown to every 1 known) to R=23.
•Nine telescopes were used for follow-up and recovery of important NEAs.•The total number of NEAs observed within the EURONEAR network reaches 739.•We present discoveries and one-night objects observed with the INT and Blanco in 34 square degrees.•We confirm past 2m and provide new 4m statistics about observability of the unknown MBAs and NEAs.•We confirm our orbital model to check any large sky survey for NEO candidates.
EUMETSAT has launched the first in a series of three Metop satellites in October 2006. Each satellite has a nominal 5 year life time, covering 14 years in total. Successive satellites will be ...launched with about 0.5 year overlap into the same sun-synchronous polar orbit, allowing inter-satellite calibration.
Focusing on the GRAS RO (radio occultation) instrument, we analyze two possible applications of this inter-satellite calibration period to assess: (1) the inherent RO precision by matching observations across the two satellites; (2) possible RO contributions to calibrate Earth-viewing sounders on-board the platforms by matching occultations with these sounders. Both applications are relevant for climate monitoring.
An inherent precision assessment depends on the applied collocation criteria. We investigate the impact on bending angle, refractivity, temperature standard deviations by collocating GRAS/COSMIC and COSMIC/COSMIC. Even with close collocations, bending angle standard deviations are never found below 1%; in refractivity processing they are reduced by a factor of more than two. In temperature, they are never below 1
K. A 1DVar based impact assessment of these criteria on the temperature error shows an additional error of about 0.3
K when moving from matches within 100–300
km. Using ECMWF data, the atmospheric variability over the investigated collocations is assessed.
With simulations we next analyze RO matches between 2 Metops with separation times of in-between 25
min and 50
min. Fairly relaxed spatial collocation criteria are required with these separation times to find strict matches, where the same GPS satellite is observed in the same viewing geometry. Such spatial collocations are unsuited to assess application (1); separation times of <6
min are required to collect enough matches. It is however possible to find more than 150 matches per day based on a criteria of ⩽300
km, ⩽3
h.
For application (2), we find collocated sounder pixels for about 90% of the occultations for collocations within ⩽100
km, ⩽
3
h, independent of whether the observations are made on the same or different platforms. Although this is reduced for close to nadir azimuth angles.
The European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) and the European Space Agency (ESA) are currently developing the Meteosat Second Generation (MSG) and the ...EUMETSAT Polar System (EPS). The first satellites in these series, MSG-1 and METOP-1 (METeorological Operational satellite) are expected to start providing validated observations of the atmosphere and the underlying surfaces in 2002 and 2005, respectively. The three MSG satellites will carry a 12-channel imager, the Spinning Enhanced Visible and Infrared Imager (SEVIRI) and a Geostationary Earth Radiation Budget (GERB) radiometer. EPS, as the European contribution to the US/European Initial Joint Polar System (IJPS), will deliver imagery and soundings from the morning orbit, while the NOAA Polar-orbiting Operational Environmental Satellite (POES) and Defense Meteorological Satellite Program (DMSP) systems will continue to cover the afternoon orbit. The MSG and EPS systems are briefly introduced with emphasis on their innovative capabilities for observing the atmosphere.
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