A5067152933- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Adaptive optics and wavefront sensing
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Optical measurement and interference techniques
- Pulsars and Gravitational Waves Research
- Scientific Research and Discoveries
- Impact of Light on Environment and Health
- Advanced Image Processing Techniques
- Radio Astronomy Observations and Technology
- Calibration and Measurement Techniques
Centre National de la Recherche Scientifique
2004-2015
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2008-2015
Astrophysique, Instrumentation et Modélisation
2008-2015
CEA Paris-Saclay
2008-2012
Osservatorio Astrofisico di Catania
2007-2010
Université Paris Cité
2008
Délégation Paris 7
2008
National Institute for Astrophysics
2007
Collège de France
2001-2006
Laboratoire de Physique Corpusculaire
2001-2006
The Shear TEsting Programme (STEP) is a collaborative project to improve the accuracy and reliability of weak lensing measurement, in preparation for next generation wide-field surveys. We review sixteen current emerging shear measurement methods common language, assess their performance by running them (blindly) on simulated images that contain known signal. determine features algorithms most successfully recover input parameters. achieve previously unattained discriminatory precision our...
The first half of this paper explores the origin systematic biases in measurement weak gravitational lensing. Compared to previous work, we expand investigation point spread function instability and fold for time effects non-idealities electronic imaging detectors imperfect galaxy shape algorithms. Together, these now explain additive |${\cal A}(\ell )$| multiplicative M}(\ell systematics typically reported current lensing measurements. We find that overall performance is driven by a product...
We present first results from the third GRavitational lEnsing Accuracy Testing (GREAT3) challenge, in a sequence of challenges for testing methods inferring weak gravitational lensing shear distortions simulated galaxy images. GREAT3 was divided into experiments to test three specific questions, and included space- ground-based data with constant or cosmologically varying fields. The simplest (control) experiment parametric galaxies realistic distribution signal-to-noise, size, ellipticity,...
Context. The control of systematic effects when measuring background galaxy shapes is one the main challenges for cosmic shear analyses.
The POINT-AGAPE collaboration is carrying out a search for gravitational microlensing toward M 31 to reveal galactic dark matter in the form of MACHOs (Massive Astrophysical Compact Halo Objects) halos Milky Way and 31. A high-threshold analysis 3 years data yields 6 bright, short-duration events, which are confronted simulation observations analysis. observed signal much larger than expected from self lensing alone we conclude, at 95% confidence level, that least 20% halo mass direction...
We report the results of our statistical study POINT-AGAPE CNe catalogue. The first Sloan $r'$ and $i'$ analysis MMRD relationship in M31 is performed using resulting CN Good fits are produced to two filters. However, we unable verify $t_{15}$ for either filter. subsequent automated detection pipeline has provided us with most thorough knowledge completeness a survey to-date. In addition, large field view permitted probe outburst rate well into galactic disk, unlike previous CCD imaging...
The light curve of PA-99-N2, one the recently announced microlensing candidates toward M31, shows small deviations from standard Paczyński form. We explore a number possible explanations, including correlations with seeing, parallax effect, and binary lens. find that observations are consistent an unresolved red giant branch or asymptotic star in M31 being microlensed by best-fit lens mass ratio is ~1.2 × 10-2, which most extreme values found for so far. If both source lie disk, then model...
We have carried out a survey of the Andromeda galaxy for unresolved microlensing (pixel lensing). present subset four short timescale, high signal-to-noise candidates found by imposing severe selection criteria: source flux variation exceeds an magnitude star and full width at half maximum timescale is less than 25 days. Remarkably, in three cases, we been able to measure or strongly constrain Einstein crossing time event. One event, which lies projected on M 31 bulge, almost certainly due...
The POINT–AGAPE (Pixel-lensing Observations with the Isaac Newton Telescope–Andromeda Galaxy Amplified Pixels Experiment) survey is an optical search for gravitational microlensing events towards Andromeda galaxy (M31). As well as microlensing, sensitive to many different classes of variable stars and transients. Here we describe automated detection selection pipeline used identify M31 classical novae (CNe) present resulting catalogue 20 CN candidates observed over three seasons. CNe are...
We present a joint weak lensing and X-ray analysis of 4 deg$^2$ from the CFHTLS XMM-LSS surveys. Our is first real survey using shapelets, new generation method. create projected mass maps images, extract 6 weak-lensing-detected clusters galaxies. show that their counts can be used to constrain power spectrum normalisation $\sigma_8 =0.92_{-0.30}^{+0.26}$ for $\Omega_m=0.24$. despite large scatter generally observed in M-T relation derived masses, tight constraints on both its slope $M_*$...
We report the discovery of a short-duration microlensing candidate in northern field POINT-AGAPE pixel lensing survey toward M31. Almost certainly, source star has been identified on Hubble Space Telescope archival images, allowing us to infer an Einstein crossing time tE = 10.4 days, maximum magnification Amax ~ 18, and lens-source proper motion μrel > 0.3 μas day-1. The event projected separation 8' from center M31, beyond bulk stellar lens population. There are three plausible...
For the purposes of identifying microlensing events, POINT-AGAPE collaboration has been monitoring Andromeda galaxy (M31) for three seasons (1999-2001) with Wide Field Camera on Isaac Newton Telescope. In each season, data are taken one hour per night roughly 60 nights during six months that M31 is visible. The two 33 × arcmin2 fields view straddle central bulge, northwards and southwards. We have calculated locations, periods brightness 35 414 variable stars in as a by-product search....
We investigate the impact of point spread function (PSF) fitting errors on cosmic shear measurements using concepts complexity and sparsity. Complexity, introduced in a previous paper, characterizes number degrees freedom PSF. For instance, an underlying PSF with model low will lead to small statistical parameters, however these parameters could suffer from large biases. Alternatively, tend reduce biases at expense errors. perform optimisation scatters by studying mean squared error model....
An automated search is carried out for microlensing events using a catalogue of 44 554 variable superpixel light curves derived from our 3-yr monitoring programme M31. Each step candidate selection objective and reproducible by computer. Our unrestricted, in the sense that it has no explicit time-scale cut. So, must overcome awkward problem distinguishing long long-period stellar variables. The basis algorithm fitting to two different theoretical models, star blended templates. Only if...
Aims. The Large Binocular Cameras (LBC) are two twin wide field cameras (FOV ~ 23'x 25') mounted at the prime foci of 8.4m Telescope (LBT). We performed a weak lensing analysis z=0.288 cluster Abell 611 on g-band data obtained by blue-optimized Camera in order to estimate mass. Methods. Due complexity PSF LBC, we decided use different approaches, KSB and Shapelets, measure shape background galaxies derive shear signal produced cluster. Then estimated mass with both aperture densitometry...
We report the discovery of a microlensing candidate projected 2'54" from center M32, on side closest to M31. The blue color (R-I= 0.00 +/- 0.14) source argues strongly that it lies in disk M31, while proximity line sight M32 implies this galaxy is most likely host lens. If interpretation correct, would confirm previous arguments front estimate order one such event or less should be present POINT-AGAPE data base. more events are discovered direction dedicated experiment, they could used...
We report the final analysis of a search for microlensing events in direction Andromeda galaxy, which aimed to probe MACHO composition M 31 halo using data collected during 1998–1999 observational campaign at MDM observatory. In previous paper, we discussed results from first set observations. Here, deal with complete set, and take advantage some INT observations 1999–2000 seasons. This merging sets taken by different instruments turns out be very useful, study longer baseline available...
Context. Weak lensing applied to deep optical images of clusters galaxies provides a powerful tool reconstruct the distribution gravitating mass associated these structures.
Cosmic shear measurements rely on our ability to measure and correct the Point Spread Function (PSF) of observations. This PSF is measured using stars in field, which give a noisy at random points field. Using Wiener filtering, we show how errors this correction process propagate into power spectrum errors. allows us test future space-based missions, such as Euclid or JDEM, thereby allowing set clear engineering specifications variability. For ground-based surveys, where variability...
The POINT-AGAPE collaboration surveyed M31 with the primary goal of optical detection microlensing events, yet its data catalog is also a prime source light curves variable and transient objects, including classical novae (CNe). A reliable means identification, combined thorough survey objects in M31, provides an excellent opportunity to locate study entire galactic population CNe. This paper presents set 440 neural networks, working 44 committees, designed specifically identify fast...
Euclid is an ESA Cosmic Vision wide-field space mission concept dedicated to the high-precision study of Dark Energy and Matter. The relies on two primary cosmological probes: Weak gravitational Lensing (WL) Baryon Acoustic Oscillations (BAO). first probe requires measurement shape photometric redshifts distant galaxies. second based 3-dimensional distribution galaxies through spectroscopic redshifts. Additional probes are also used include cluster counts, redshift distortions, integrated...
Searching for microlensing in M31 using automated superpixel surveys raises a number of difficulties which are not present more conventional techniques. Here we focus on the problem that list candidates is sensitive to selection criteria or 'cuts' imposed, and some subjectivity involved this. Weakening cuts will generate longer but with greater fraction spurious ones; strengthening produce shorter may exclude genuine events. We illustrate this by comparing three analyses same data set...