The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
J L Starck - One of the best experts on this subject based on the ideXlab platform.
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multi band morpho Spectral Component analysis deblending tool muscadet deblending colourful objects
Astronomy and Astrophysics, 2016Co-Authors: R Joseph, F Courbin, J L StarckAbstract:We introduce a new algorithm for colour separation and deblending of multi-band astronomical images called MuSCADeT which is based on Morpho-Spectral Component Analysis of multi-band images. The MuSCADeT algorithm takes advantage of the sparsity of astronomical objects in morphological dictionaries such as wavelets and their differences in Spectral energy distribution (SED) across multi-band observations. This allows us to devise a model independent and automated approach to separate objects with different colours. We show with simulations that we are able to separate highly blended objects and that our algoonfront our algoritrithm is robust against SED variations of objects across the field of view. To chm with real data, we use HST images of the strong lensing galaxy cluster MACS J1149+2223 and we show that MuSCADeT performs better than traditional profile-fitting techniques in deblending the foreground lensing galaxies from background lensed galaxies. Although the main driver for our work is the deblending of strong gravitational lenses, our method is fit to be used for any purpose related to deblending of objects in astronomical images. An example of such an application is the separation of the red and blue stellar populations of a spiral galaxy in the galaxy cluster Abell 2744. We provide a python package along with all simulations and routines used in this paper to contribute to reproducible research efforts.
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multi band morpho Spectral Component analysis deblending tool muscadet deblending colourful objects
arXiv: Instrumentation and Methods for Astrophysics, 2016Co-Authors: R Joseph, F Courbin, J L StarckAbstract:We introduce a new algorithm for colour separation and deblending of multi-band astronomical images called MuSCADeT which is based on Morpho-Spectral Component Analysis of multi-band images. The MuSCADeT algorithm takes advantage of the sparsity of astronomical objects in morphological dictionaries such as wavelets and their differences in Spectral energy distribution (SED) across multi-band observations. This allows us to devise a model independent and automated approach to separate objects with different colours. We show with simulations that we are able to separate highly blended objects and that our algorithm is robust against SED variations of objects across the field of view. To confront our algorithm with real data, we use HST images of the strong lensing galaxy cluster MACS J1149+2223 and we show that MuSCADeT performs better than traditional profile-fitting techniques in deblending the foreground lensing galaxies from background lensed galaxies. Although the main driver for our work is the deblending of strong gravitational lenses, our method is fit to be used for any purpose related to deblending of objects in astronomical images. An example of such an application is the separation of the red and blue stellar populations of a spiral galaxy in the galaxy cluster Abell 2744. We provide a python package along with all simulations and routines used in this paper to contribute to reproducible research efforts. Codes can be found at this http URL
R Joseph - One of the best experts on this subject based on the ideXlab platform.
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multi band morpho Spectral Component analysis deblending tool muscadet deblending colourful objects
Astronomy and Astrophysics, 2016Co-Authors: R Joseph, F Courbin, J L StarckAbstract:We introduce a new algorithm for colour separation and deblending of multi-band astronomical images called MuSCADeT which is based on Morpho-Spectral Component Analysis of multi-band images. The MuSCADeT algorithm takes advantage of the sparsity of astronomical objects in morphological dictionaries such as wavelets and their differences in Spectral energy distribution (SED) across multi-band observations. This allows us to devise a model independent and automated approach to separate objects with different colours. We show with simulations that we are able to separate highly blended objects and that our algoonfront our algoritrithm is robust against SED variations of objects across the field of view. To chm with real data, we use HST images of the strong lensing galaxy cluster MACS J1149+2223 and we show that MuSCADeT performs better than traditional profile-fitting techniques in deblending the foreground lensing galaxies from background lensed galaxies. Although the main driver for our work is the deblending of strong gravitational lenses, our method is fit to be used for any purpose related to deblending of objects in astronomical images. An example of such an application is the separation of the red and blue stellar populations of a spiral galaxy in the galaxy cluster Abell 2744. We provide a python package along with all simulations and routines used in this paper to contribute to reproducible research efforts.
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multi band morpho Spectral Component analysis deblending tool muscadet deblending colourful objects
arXiv: Instrumentation and Methods for Astrophysics, 2016Co-Authors: R Joseph, F Courbin, J L StarckAbstract:We introduce a new algorithm for colour separation and deblending of multi-band astronomical images called MuSCADeT which is based on Morpho-Spectral Component Analysis of multi-band images. The MuSCADeT algorithm takes advantage of the sparsity of astronomical objects in morphological dictionaries such as wavelets and their differences in Spectral energy distribution (SED) across multi-band observations. This allows us to devise a model independent and automated approach to separate objects with different colours. We show with simulations that we are able to separate highly blended objects and that our algorithm is robust against SED variations of objects across the field of view. To confront our algorithm with real data, we use HST images of the strong lensing galaxy cluster MACS J1149+2223 and we show that MuSCADeT performs better than traditional profile-fitting techniques in deblending the foreground lensing galaxies from background lensed galaxies. Although the main driver for our work is the deblending of strong gravitational lenses, our method is fit to be used for any purpose related to deblending of objects in astronomical images. An example of such an application is the separation of the red and blue stellar populations of a spiral galaxy in the galaxy cluster Abell 2744. We provide a python package along with all simulations and routines used in this paper to contribute to reproducible research efforts. Codes can be found at this http URL
Francesco Di Palma - One of the best experts on this subject based on the ideXlab platform.
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terrestrial gamma ray flashes as powerful particle accelerators
Physical Review Letters, 2011Co-Authors: M Tavani, M Marisaldi, C Labanti, F Fuschino, A Argan, A Trois, P Giommi, S Colafrancesco, C Pittori, Francesco Di PalmaAbstract:Strong electric discharges associated with thunderstorms can produce terrestrial gamma-ray flashes (TGFs), i.e., intense bursts of x rays and γ rays lasting a few milliseconds or less. We present in this Letter new TGF timing and Spectral data based on the observations of the Italian Space Agency AGILE satellite. We determine that the TGF emission above 10 MeV has a significant power-law Spectral Component reaching energies up to 100 MeV. These results challenge TGF theoretical models based on runaway electron acceleration. The TGF discharge electric field accelerates particles over the large distances for which maximal voltages of hundreds of megavolts can be established. The combination of huge potentials and large electric fields in TGFs can efficiently accelerate particles in large numbers, and we reconsider here the photon spectrum and the neutron production by photonuclear reactions in the atmosphere.
M Marisaldi - One of the best experts on this subject based on the ideXlab platform.
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on the high energy Spectral Component and fine time structure of terrestrial gamma ray flashes
arXiv: Space Physics, 2021Co-Authors: M Marisaldi, M Galli, C Labanti, N Ostgaard, D Sarria, Steven A Cummer, Fanchao Lyu, Anders Lindanger, R CampanaAbstract:Terrestrial gamma ray flashes (TGFs) are very short bursts of gamma radiation associated to thunderstorm activity and are the manifestation of the highest-energy natural particle acceleration phenomena occurring on Earth. Photon energies up to several tens of megaelectronvolts are expected, but the actual upper limit and high-energy Spectral shape are still open questions. Results published in 2011 by the AGILE team proposed a high-energy Component in TGF spectra extended up to $\approx$100 MeV, which is difficult to reconcile with the predictions from the Relativistic Runaway Electron Avalanche (RREA) mechanism at the basis of many TGF production models. Here we present a new set of TGFs detected by the AGILE satellite and associated to lightning measurements capable to solve this controversy. Detailed end-to-end Monte Carlo simulations and an improved understanding of the instrument performance under high-flux conditions show that it is possible to explain the observed high-energy counts by a standard RREA spectrum at the source, provided that the TGF is sufficiently bright and short. We investigate the possibility that single high-energy counts may be the signature of a fine-pulsed time structure of TGFs on time scales $\approx$4 {\mu}s, but we find no clear evidence for this. The presented data set and modeling results allow also for explaining the observed TGF distribution in the (Fluence x duration) parameter space and suggest that the AGILE TGF detection rate can almost be doubled. Terrestrial gamma ray flashes (TGFs) are very short bursts of gamma radiation associated to thunderstorm activity and are the manifestation of the highest-energy natural particle acceleration phenomena occurring on Earth. (...continues)
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terrestrial gamma ray flashes as powerful particle accelerators
Physical Review Letters, 2011Co-Authors: M Tavani, M Marisaldi, C Labanti, F Fuschino, A Argan, A Trois, P Giommi, S Colafrancesco, C Pittori, Francesco Di PalmaAbstract:Strong electric discharges associated with thunderstorms can produce terrestrial gamma-ray flashes (TGFs), i.e., intense bursts of x rays and γ rays lasting a few milliseconds or less. We present in this Letter new TGF timing and Spectral data based on the observations of the Italian Space Agency AGILE satellite. We determine that the TGF emission above 10 MeV has a significant power-law Spectral Component reaching energies up to 100 MeV. These results challenge TGF theoretical models based on runaway electron acceleration. The TGF discharge electric field accelerates particles over the large distances for which maximal voltages of hundreds of megavolts can be established. The combination of huge potentials and large electric fields in TGFs can efficiently accelerate particles in large numbers, and we reconsider here the photon spectrum and the neutron production by photonuclear reactions in the atmosphere.
B. Paul - One of the best experts on this subject based on the ideXlab platform.
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timing and Spectral studies of lmc x 4 in high and low states with bepposax detection of pulsations in the soft Spectral Component
The Astrophysical Journal, 2004Co-Authors: S Naik, B. PaulAbstract:We report here detailed timing and Spectral analysis of two BeppoSAX observations of the binary X-ray pulsar LMC X-4 carried out during the low and high states of its 30.5 day long superorbital period. Timing analysis clearly shows 13.5 s X-ray pulsations in the high state of the superorbital period, which allows us to measure the mideclipse time during this observation. Combining this with two other mideclipse times derived earlier with ASCA, we have derived a new estimate of the orbital period derivative. Pulse-phase-averaged spectroscopy in the high and low states shows that the energy spectrum in the 0.1-10 keV band comprises a hard power law, a soft excess, and a strong iron emission line. The continuum flux is found to decrease by a factor of ~60 in the low state, while the decrease in the iron-line flux is only by a factor of ~12, suggesting a different site for the production of the line emission. In the low state, we have not found any significant increase in the absorption column density. The X-ray emission is found to come from a very large region, comparable to the size of the companion star. Pulse-phase-resolved spectroscopy in the high state shows a pulsating nature of the soft Spectral Component with some phase offset compared to the hard X-rays, as is known in some other binary X-ray pulsars.
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nature of the soft Spectral Component in the x ray pulsars smc x 1 and lmc x 4
The Astrophysical Journal, 2002Co-Authors: B. Paul, Fumiaki Nagase, Tadayasu Dotani, Jun Yokogawa, T. Endo, Mamiko NishiuchiAbstract:We present here the results of an investigation of the pulse-averaged and pulse-phase-resolved energy spectra of two high-luminosity accretion-powered X-ray pulsars SMC X-1 and LMC X-4 made with ASCA. The phase-averaged energy spectra definitely show the presence of a soft excess in both sources. If the soft excess is modeled as a separate blackbody- or thermal-bremsstrahlung-type Component, pulse-phase-resolved spectroscopy of SMC X-1 shows that the soft Component also has a pulsating nature. The same may be true for LMC X-4, although a very small pulse fraction limits the statistical significance. The pulsating soft Component is found to have a nearly sinusoidal profile, dissimilar to the complex profile seen at higher energies, which can be an effect of smearing. Due to the very high luminosity of these sources, the size of the emission zone required for the soft Component is large (radius ~300-400 km). We show that the pulsating nature of the soft Component is difficult to explain if a thermal origin is assumed for it. We further investigate with alternate models, such as an inversely broken power law or two different power-law Components, and find that these models can also be used to explain the excess at low energy. A soft power-law Component may be a common feature of accreting X-ray pulsars, which is difficult to detect because most high-mass X-ray binary pulsars are in the Galactic plane and experience large interstellar absorption. In LMC X-4, we have also measured two additional mideclipse times, which confirm the known orbital decay.
