A5041586011- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Adaptive optics and wavefront sensing
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Astrophysical Phenomena and Observations
- Cosmology and Gravitation Theories
- History and Developments in Astronomy
- Geophysics and Gravity Measurements
- Radio Astronomy Observations and Technology
- Scientific Research and Discoveries
- Photocathodes and Microchannel Plates
- Impact of Light on Environment and Health
- Historical Astronomy and Related Studies
- Astrophysics and Cosmic Phenomena
- Digital and Traditional Archives Management
- Pulsars and Gravitational Waves Research
- Spectroscopy and Laser Applications
- Advanced optical system design
- Isotope Analysis in Ecology
- CCD and CMOS Imaging Sensors
- Atmospheric Ozone and Climate
Observatoire de Paris
2016-2025
Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères
2016-2025
Centre National de la Recherche Scientifique
2014-2025
University of Arizona
2022-2024
Université Paris Cité
2021
Sorbonne Université
2021
Université Paris Sciences et Lettres
2021
University of Cambridge
1993-2016
Galaxies, Etoiles, Physique et Instrumentation
2006-2014
Institute of High Energy Physics
2013-2014
In `A Bayesian Approach to Locating the Red Giant Branch Tip Magnitude (PART I),' a new technique was introduced for obtaining distances using TRGB standard candle. Here we describe useful complement with potential further reduce uncertainty in our distance measurements by incorporating matched-filter weighting scheme into model likelihood calculations. this scheme, stars are weighted according their probability of being true object members. We then re-test modified algorithm...
The Pan-Andromeda Archaeological Survey is a survey of $>400$ square degrees centered on the Andromeda (M31) and Triangulum (M33) galaxies that has provided most extensive panorama $L_\star$ galaxy group to large projected galactocentric radii. Here, we collate summarise current status our knowledge substructures in stellar halo M31, discuss connections between these features. We estimate 13 distinctive were produced by at least 5 different accretion events, all last 3 or 4 Gyrs. suggest few...
Abstract The claimed detection of a diffuse galaxy lacking dark matter represents possible challenge to our understanding the properties these galaxies and formation in general. galaxy, already identified photographic plates taken summer 1976 at UK 48-in Schmidt telescope, presents normal distance-independent (e.g. colour, velocity dispersion its globular clusters). However, distance-dependent quantities are odds with those other similar galaxies, namely luminosity function sizes clusters,...
ABSTRACT We report the discovery of DGSAT I, an ultra-diffuse, quenched galaxy located 10.°4 in projection from Andromeda (M31). This low-surface brightness ( μ V = 24.8 mag arcsec −2 ), found with a small amateur telescope, appears unresolved sub-arcsecond archival Subaru/Suprime-Cam images, and hence has been missed by optical surveys relying on resolved star counts, spite its relatively large effective radius R e ) 12″) proximity (15′) to well-known dwarf spheroidal And II. Its red color...
Aims.We present data from the CFHTLS Strong Lensing Legacy Survey (SL2S). Due to unsurpassed combined depth, area and image quality of Canada-France-Hawaii it is becoming possible uncover a large, statistically well-defined sample strong gravitational lenses which spans dark halo mass spectrum predicted by concordance model galaxy cluster haloes.
AIMS: We present data from the CFHTLS Strong Lensing Legacy Survey (SL2S). Due to unsurpassed combined depth, area and image quality of Canada-France-Hawaii it is becoming possible uncover a large, statistically well-defined sample strong gravitational lenses which spans dark halo mass spectrum predicted by concordance model galaxy cluster haloes. METHODS: describe development several automated procedures find various regimes in images. RESULTS: The preliminary about 40 lensing candidates...
We present measurements of 68 classical Cepheids with periods from 10 to 78 days observed in the near-infrared by PHAT Program using Wide Field Camera 3 (WFC3) on Hubble Space Telescope (HST). The combination HST's resolution and use provides a dramatic reduction dispersion Period--Luminosity relation over optical, ground-based data. Even random-phase magnitudes we measure just 0.17 mag, implying 0.12 mag for mean magnitudes. error this is 1% distance. Combined similar observations other...
Super-Eddington accreting massive black holes (SEAMBHs) reach saturated luminosities above a certain accretion rate due to photon trapping and advection in slim disks. We show that these SEAMBHs could provide new tool for estimating cosmological distances if they are properly identified by hard x-ray observations, particular the slope of their 2--10 keV continuum. To verify this idea we obtained hole mass estimates data sample 60 narrow line Seyfert 1 galaxies consider be most promising...
We undertake an investigation into the spatial structure of M31 satellite system utilizing distance distributions presented in a previous publication. These distances make use unique combination depth and coverage Pan-Andromeda Archaeological Survey (PAndAS) to provide large, homogeneous sample consisting 27 M31's satellites, as well itself. find that distribution, when viewed whole, is no more planar than one would expect from random distribution equal size. A disk 15 satellites however...
We reveal the highly structured nature of Milky Way (MW) stellar halo within footprint Pan-Andromeda Archaeological Survey (PAndAS) photometric survey from blue main sequence (MS) and MS turn-off stars. map no fewer than five structures a heliocentric range ∼5–30 kpc. Some these are known (the Monoceros Ring, Pisces/Triangulum globular cluster stream), but we also uncover three well-defined that could be, at least partly, responsible for so-called Triangulum/Andromeda 2 features. In...
Distance determinations of extremely-low-surface-brightness galaxies are expensive in terms spectroscopic time. Because this, their distances often inferred by associating such with larger structures as groups or clusters, leading to a systematic bias selecting objects high density environments. Here we report the discovery red ultra-diffuse galaxy (S82-DG-1: $r_{\mathrm{eff}}$ = 1.6 kpc; $<\mu _{g}>$ 25.7 mag arcsec$^{-2}$; $g-i$ 0.78 mag) located nearby cosmic void. We used multi-band...
We use recent Hubble Space Telescope colour-magnitude diagrams of the resolved stellar populations a sample local dSph galaxies (Carina, Leo I, II and Ursa Minor) to infer star formation histories these systems, SFR(t). Applying new variational calculus maximum likelihood method, which includes full Bayesian analysis allows non-parametric estimate function one is solving for, we systems studied. This method has advantage yielding an objective answer, as need not assume priori form trying...
We perform a discrete wavelet analysis of the Cosmic Background Explorer differential microwave radiometer (DMR) 4-yr sky maps and find significant scale-scale correlation on angular scales from about 11\ifmmode^\circ\else\textdegree\fi{} to 22\ifmmode^\circ\else\textdegree\fi{}, only in DMR face centered north galactic pole. This non-Gaussian signature does not arise either known foregrounds or correlated noise maps, nor is it consistent with upper limits residual systematic errors maps....
Analysis pipelines commonly use high-level technologies that are popular when created, but unlikely to be readable, executable, or sustainable in the long term. A set of criteria is introduced address this problem: Completeness (no execution requirement beyond a minimal Unix-like operating system, no administrator privileges, network connection, and storage primarily plain text); modular design; complexity; scalability; verifiable inputs outputs; version control; linking analysis with...
Abstract We used the Condor Array Telescope to obtain deep imaging observations through luminance broadband and He ii 468.6 nm, [O iii ] 500.7 i 587.5 H α , [N 658.4 [S 671.6 nm narrowband filters of an extended region comprising 13 “Condor fields” spanning ≈ 8 × deg 2 on sky centered near M81 M82. Here we describe acquisition processing these observations, which together constitute unique very a large portion Group complement broad- filters. The images are characterized by intricate web...
In the pursuit of observing fainter astronomical sources and phenomena, a significant challenge in detector development lies ensuring that these devices can detect each individual photon they receive. By amplifying incoming by several orders magnitude, electron-multiplying charge-coupled (EMCCDs) offer promising solution to meet this challenge. Although detectors boast impressive potential, be intricate, requiring precise optimization fine-tuning their parameters unlock full capabilities...
Thin stellar streams, such as those resulting from the tidal disruption of globular clusters, have long been known and used probes gravitational potential our Galaxy, both its visible dark contents. In particular, presence under-density regions, or gaps, along these streams is commonly interpreted being due to close passage matter sub-halos. this work, we investigate perturbations induced on by dense systems, clusters themselves, test possibility that they may cause formation gaps well....
Abstract We used the Condor Array Telescope to obtain deep imaging observations through luminance broadband and He ii , [O iii ], i H α [N [S ] narrowband filters of an extended region M81 Group spanning ≈8 × 8 deg 2 on sky centered near M82. Here, we report aspects these that are specifically related (1) a remarkable filament known as “Ursa Major Arc” stretches ≈30° across roughly in direction Ursa Major, (2) “giant shell ionized gas” ≈0.8 located ≈0.6 northwest M82, (3) network gaseous...
In terms of statistical fluctuations, stellar population synthesis models are only asymptotically correct in the limit a large number stars, where sampling errors become small. When dealing with clusters, starbursts, dwarf galaxies or populations within pixels, introduce dispersion predicted integrated properties these populations. We present here an approximate but generic formalism which allows very good estimation uncertainties and confidence levels any property, bypassing extensive Monte...
We report the detection of a pair degree-long tidal tails associated with globular cluster Palomar 14, using images obtained at Canada–France–Hawaii Telescope. reveal power-law departure from King profile large distances to center. The density map constructed optimal matched filter technique shows nearly symmetrical and elongated distribution stars on both sides cluster, forming an S-shape characteristic mass loss. This evidence may be telltale signature stripping in action. This, together...