N. A. Walton
A5065346852- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Astrophysics and Star Formation Studies
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Adaptive optics and wavefront sensing
- Geophysics and Gravity Measurements
- Astrophysical Phenomena and Observations
- Scientific Research and Discoveries
- Solar and Space Plasma Dynamics
- History and Developments in Astronomy
- Cosmology and Gravitation Theories
- Distributed and Parallel Computing Systems
- Geomagnetism and Paleomagnetism Studies
- Breast Cancer Treatment Studies
- Radiomics and Machine Learning in Medical Imaging
- Calibration and Measurement Techniques
- Scientific Computing and Data Management
- Dark Matter and Cosmic Phenomena
- Earth Systems and Cosmic Evolution
- Cancer Genomics and Diagnostics
University of Cambridge
2016-2025
Institute of Astronomy
2006-2025
Search for Extraterrestrial Intelligence
2024
University of Turin
2022
Engineering Arts (United States)
2021
Allen Institute
2021
Howard Hughes Medical Institute
2021
IIT@MIT
2021
McGovern Institute for Brain Research
2021
National Heart Foundation of Australia
2021
We report measurements of the mass density, ΩM, and cosmological-constant energy ΩΛ, universe based on analysis 42 type Ia supernovae discovered by Supernova Cosmology Project. The magnitude-redshift data for these supernovae, at redshifts between 0.18 0.83, are fitted jointly with a set from Calán/Tololo Survey, below 0.1, to yield values cosmological parameters. All supernova peak magnitudes standardized using SN light-curve width-luminosity relation. measurement yields joint probability...
We present distance measurements to 71 high redshift type Ia supernovae discovered during the first year of 5-year Supernova Legacy Survey (SNLS). These events were detected and their multi-color light-curves measured using MegaPrime/MegaCam instrument at Canada-France-Hawaii Telescope (CFHT), by repeatedly imaging four one-square degree fields in bands, as part CFHT (CFHTLS). Follow-up spectroscopy was performed VLT, Gemini Keck telescopes confirm nature measure redshift. With this data...
Aims. We present cosmological constraints from a joint analysis of type Ia supernova (SN Ia) observations obtained by the SDSS-II and SNLS collaborations. The dataset includes several low-redshift samples (z< 0.1), all three seasons (0.05 <z< 0.4), years (0.2 1), it totals 740 spectroscopically confirmed supernovae with high-quality light curves.
We report measurements of ΩM, ΩΛ, and w from 11 supernovae (SNe) at z = 0.36-0.86 with high-quality light curves measured using WFPC2 on the Hubble Space Telescope (HST). This is an independent set high-redshift SNe that confirms previous SN evidence for accelerating universe. The available photometry make it possible these alone to provide cosmological parameters comparable in statistical weight results. Combined earlier Supernova Cosmology Project data, new yield a measurement mass density...
We present a new compilation of Type Ia supernovae (SNe Ia), dataset low-redshift nearby-Hubble-flow SNe and analysis procedures to work with these heterogeneous compilations. This ``Union'' 414 SN Ia, which reduces 307 after selection cuts, includes the recent large samples from Supernova Legacy Survey ESSENCE Survey, older datasets, as well recently extended distant observed HST. A single, consistent blind procedure is used for all various subsamples, implemented that consistently weights...
We use Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5) u, g, r, i, z photometry to study Milky Way halo substructure in the area around north Galactic cap. A simple color cut (g - r < 0.4) reveals tidal stream of Sagittarius dwarf spheroidal galaxy, as well a number other stellar structures field. Two branches (A and B) are clearly visible an RGB composite image created from three magnitude slices, there is also evidence for still more distant wrap behind branch. comparison these data...
Aims. We describe the photometric content of second data release Gaia project (Gaia DR2) and its validation along with quality data. Methods. The was mainly carried out using an internal analysis photometry. External comparisons were also made, but limited by precision systematics that may be present in external catalogues used. Results. In addition to assessment, we best estimates three passbands. Various colour-colour transformations are derived enable users convert between commonly used...
Gaia Early Data Release 3 contains astrometry and photometry results for about 1.8 billion sources based on observations collected by the ESA satellite during first 34 months of operations. This paper focuses photometric content, describing input data, algorithms, processing, validation results. Particular attention is given to quality data a number features that users may need take into account make best use EDR3 catalogue. The treatment BP RP background has been updated include better...
The goal of this paper is to demonstrate the outstanding quality second data release Gaia mission and its power for constraining many different aspects dynamics satellites Milky Way. We focus here on determining proper motions 75 Galactic globular clusters, nine dwarf spheroidal galaxies, one ultra-faint system, Large Small Magellanic Clouds. Using extracted from archive, we derived parallaxes these systems, as well their uncertainties. that errors, statistical systematic, are relatively...
Before the publication of Gaia Catalogue, contents first data release have undergone multiple dedicated validation tests. These tests aim at analysing in-depth Catalogue content to detect anomalies, individual problems in specific objects or overall statistical properties, either filter them before public release, describe different caveats for an optimal exploitation data. Dedicated methods using internal data, external catalogues models been developed processes. They are testing normal...
The INT Photometric Halpha Survey of the Northern Galactic Plane (IPHAS) is a 1800 square degrees CCD survey northern Milky Way spanning latitude range -5 < b +5 (degrees) and reaching down to r' ~ 20 (10-sigma). It may increase number known emission line sources by an order magnitude. Representative observations assessment point-source data from IPHAS, now underway, are presented. obtained Wide Field Camera images in narrow-band, Sloan i' broad-band, filters. We simulate IPHAS (r' -...
We produce a clean and well-characterised catalogue of objects within 100\,pc the Sun from \G\ Early Data Release 3. characterise through comparisons to full data release, external catalogues, simulations. carry out first analysis science that is possible with this sample demonstrate its potential best practices for use. The selection used selected training sets, machine-learning procedures, astrometric quantities, solution quality indicators determine probability reliable. set construction...
The VST Photometric Halpha Survey of the Southern Galactic Plane and Bulge (VPHAS+) is surveying southern Milky Way in u, g, r, i at 1 arcsec angular resolution. Its footprint spans latitude range -5 < b +5 all longitudes south celestial equator. Extensions around Centre to latitudes +/-10 bring much Bulge. This ESO public survey, begun on 28th December 2011, reaches down 20th magnitude (10-sigma) will provide single-epoch digital optical photometry for 300 million stars. observing strategy...
To illustrate the potential of GDR2, we provide a first look at kinematics Milky Way disc, within radius several kiloparsecs around Sun. We benefit for time from sample 6.4 million F-G-K stars with full 6D phase-space coordinates, precise parallaxes, and Galactic cylindrical velocities . From this sample, extracted sub-sample 3.2 giant to map velocity field disc $\sim$5~kpc $\sim$13~kpc centre up 2~kpc above below plane. also study distribution 0.3 solar neighbourhood ($r < 200$~pc), median...
The Gaia-ESO Survey is obtaining high-quality spectroscopic data for about 10^5 stars using FLAMES at the VLT. UVES high-resolution spectra are being collected 5000 FGK-type stars. These analyzed in parallel by several state-of-the-art methodologies. Our aim to present how these analyses were implemented, discuss their results, and describe a final recommended parameter scale defined. We also precision (method-to-method dispersion) accuracy (biases with respect reference values) of...
The Public European Southern Observatory Spectroscopic Survey of Transient Objects (PESSTO) began as a public spectroscopic survey in April 2012. We describe the data reduction strategy and products which are publicly available through ESO archive Data Release 1 (SSDR1). PESSTO uses New Technology Telescope with EFOSC2 SOFI to provide optical NIR spectroscopy imaging. target supernovae transients brighter than 20.5mag for classification. Science targets then selected follow-up based on...
Abstract A holistic understanding of tissue and organ structure function requires the detection molecular constituents in their original three-dimensional (3D) context. Imaging mass cytometry (IMC) enables simultaneous up to 40 antigens transcripts using metal-tagged antibodies but has so far been restricted two-dimensional imaging. Here we report development 3D IMC for multiplexed analysis at single-cell resolution demonstrate utility technology by human breast cancer samples. The resulting...
(Abridged) Blue (BP) and Red (RP) Photometer low-resolution spectral data is one of the exciting new products in Gaia Data Release 3 (Gaia DR3). We calibrate about 65 billion individual transit spectra onto same mean BP/RP instrument through a series calibration steps, including background subtraction, CCD geometry an iterative procedure for efficiency as well variations line-spread function dispersion across focal plane time. The calibrated are then combined each source terms expansion into...