A5011038790- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Galaxies: Formation, Evolution, Phenomena
- Astro and Planetary Science
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Adaptive optics and wavefront sensing
- History and Developments in Astronomy
- Solar and Space Plasma Dynamics
- Astrophysics and Cosmic Phenomena
- Geophysics and Gravity Measurements
- Laser Design and Applications
- Experimental and Theoretical Physics Studies
- Dark Matter and Cosmic Phenomena
- Historical Astronomy and Related Studies
- Spectroscopy and Laser Applications
- Astronomical Observations and Instrumentation
Observatoire de la Côte d’Azur
2019-2023
Centre National de la Recherche Scientifique
2019-2023
Université Côte d'Azur
2019-2023
Max Planck Institute for Extraterrestrial Physics
2013-2019
Lagrange Laboratory
2019
Optica
2013-2015
Max Planck Society
2013-2015
California Institute of Technology
2011-2012
The inner Milky Way is dominated by a boxy, triaxial bulge which believed to have formed through disc instability processes. Despite its proximity, large-scale properties are still not very well known, due our position in the obscuring Galactic disc. Here, we make measurement of three-dimensional density distribution using red clump giants identified DR1 Vista Variables Via Lactea survey. Our map covers (2.2 × 1.4 1.1) kpc bulge/bar. Line-of-sight distributions estimated deconvolving...
While it is incontrovertible that the inner Galaxy contains a bar, its structure near Galactic plane has remained uncertain, where extinction from intervening dust greatest. We investigate here bar outside bulge, long using red clump giant (RCG) stars UKIDSS, 2MASS, VVV, and GLIMPSE. match combine these surveys to wide area in latitude longitude, |b|<9deg |l|<40deg. find: (1) The extends l~25deg at |b|~5deg plane, l~30deg lower latitudes. (2) an angle line-of-sight range (28-33)deg,...
We construct a large set of dynamical models the galactic bulge, bar and inner disc using made-to-measure method. Our are constrained to match red clump giant density from combination VVV, UKIDSS 2MASS infrared surveys together with stellar kinematics in bulge BRAVA OGLE surveys, entire region ARGOS Survey. able recover pattern speed dark matter mass distributions region, thus recovering effective potential. find 39.0 ± 3.5 km s− 1 kpc− 1, placing corotation radius at 6.1 0.5 kpc making...
We derive new constraints on the mass, rotation, orbit structure and statistical parallax of Galactic old nuclear star cluster (NSC) mass supermassive black hole. combine counts kinematic data from Fritz et al (2014), including 2'500 line-of-sight velocities 10'000 proper motions. show that difference between motion dispersions sigma_l sigma_b cannot be explained by but is a consequence flattening NSC. fit surface density distribution stars in central 1000" spheroidal with scale ~100" much...
We construct dynamical models of the Milky Way's Box/Peanut (B/P) bulge, using recently measured 3D density Red Clump Giants (RCGs) as well kinematic data from BRAVA survey. match these NMAGIC Made-to-Measure method, starting with N-body for barred discs in different dark matter haloes. determine total mass bulge volume RCGs measurement (+-2.2 x +- 1.4 1.2 kpc) unprecedented accuracy and robustness to be 1.84 0.07 x10^10 Msun. The stellar this varies between 1.25-1.6 Msun, depending on...
We investigate interstellar extinction curve variations toward $\sim$4 deg$^{2}$ of the inner Milky Way in $VIJK_{s}$ photometry from OGLE-III and $VVV$ surveys, with supporting evidence diffuse bands $F435W,F625W$ photometry. obtain independent measurements $\sim$2,000 sightlines $A_{I}$, $E(V-I)$, $E(I-J)$, $E(J-K_{s})$, median precision accuracy 2%. find that ratios $A_{I}/E(V-I)$, $E(I-J)/E(V-I)$ $E(J-K_{s})/E(V-I)$ are large (exceeding 20%), significant, positively correlated, as...
From a sample of 15651 RR Lyrae with accurate proper motions in Gaia DR2, we measure the azimuthally averaged kinematics inner stellar halo between 1.5 kpc and 20 from Galactic centre. We find that their are strongly radially anisotropic, velocity ellipsoid nearly spherically aligned over this volume. Only regions $\lesssim$ 5 does anisotropy significantly fall (but still $β>$ 0.25) tilt towards cylindrical alignment. In regions, our stars rotates at up to 50 km s$^{-1}$, which may...
The second data release of the Gaia mission has revealed a very rich structure in local velocity space. In terms in-plane motions, this is also seen as multiple ridges actions axisymmetric background potential Galaxy. These are probably related to combination effects from ongoing phase-mixing and resonances spiral arms bar. We have recently developed method for capturing behaviour stellar phase-space distribution function at resonance by re-expressing it new set canonical angles variables...
Abstract We have derived absolute proper motions of the entire Galactic bulge region from VVV Infrared Astrometric Catalogue (VIRAC) and Gaia. present these both as integrated on-sky maps and, after isolating standard candle red clump (RC) stars, a function distance using RC magnitude proxy. These data provide new global, 3D view Milky Way barred kinematics. find gradient in mean longitudinal motion, $\langle \mu _ l^\star \rangle $, between different sides bar, which is sensitive to bar...
Recent observations have discovered the presence of a Box/Peanut or X-shape structure in Galactic bulge. Such structures are common external disc galaxies, and well-known N-body simulations where they form following buckling instability bar. From studies analytical potentials models it has been claimed past that bulges supported by "bananas", x1v1 orbits. We present here set instead peanut bulge is mainly brezel-like orbits, allowing strong peanuts to with short extent relative bar length....
Microlensing provides a unique tool to break the stellar dark matter degeneracy in inner Milky Way. We combine N-body dynamical models fitted Way's Boxy/Peanut bulge with exponential disc outside this, and compute microlensing properties. Considering range of consistent revised MOA-II data, we find low fractions Galaxy: at peak their rotation curve fraction fv = (0.88 ± 0.07) circular velocity is baryonic (at 1σ, > 0.72 2σ). These results are agreement constraints from EROS-II survey...
We propose a novel explanation for the Hercules stream consistent with recent measurements of extent and pattern speed Galactic bar. have adapted made-to-measure dynamical model tailored Milky Way to investigate kinematics solar neighborhood (SNd). The matches 3D density red clump giant stars (RCGs) in bulge bar as well stellar inner Galaxy, 39 km s$^{-1}$ kpc$^{-1}$. Cross-matching this $Gaia$ DR1 TGAS data combined RAVE LAMOST radial velocities, we find that naturally predicts bimodality...
ABSTRACT We study the late-time evolution of central regions two Milky Way (MW)-like simulations galaxies formed in a cosmological context, one hosting fast bar and other slow one. find that length, Rb, measurements fluctuate on dynamical time-scale by up to 100 per cent, depending spiral structure strength measurement threshold. The amplitude oscillates about 15 correlating with Rb. Tremaine–Weinberg method estimates bars’ instantaneous pattern speeds show variations around mean $\sim...
We find that the majority of systems hosting multiple tidal disruptions are likely to contain hard binary SMBH systems, and also show rates these repeated events high enough be detected by LSST over its lifetime. Therefore, disruption provide a novel method identify super-massive black hole (SMBH) with parsec sub-parsec separations. The investigated using simulations non-interacting stars initially orbiting primary potential model stellar cusp. then evolved forward in time perturbed...
We present the first self-consistent chemodynamical model fitted to reproduce data for galactic bulge, bar and inner disc. extend Made-to-Measure method an augmented phase-space including metallicity of stars, show its application region Milky Way. Using from ARGOS APOGEE (DR12) surveys, we adapt recent dynamical Portail et al. observed spatial kinematic variations as a function metallicity, thus allowing detailed study 3D density distributions, kinematics orbital structure stars in...
We consider the formation of extreme mass-ratio inspirals (EMRIs) sourced from a stellar cusp centred on primary supermassive black hole (SMBH) and perturbed by an inspiraling less massive secondary SMBH. The problem is approached numerically, assuming stars are non-interacting over these short time-scales performing ensemble restricted three-body integrations. From simulations, we see that not only can EMRIs be produced during this process, but dynamics also quite rich. In particular, most...
We present gas flow models for the Milky Way based on high-resolution grid-based hydrodynamical simulations. The basic galactic potential we use is from a N-body model constrained by density of red clump giants in Galactic bulge. augment this with nuclear bulge, two pairs spiral arms and additional mass at bar end to represent long component. With combined can reproduce many features observed ($l,v$) diagram pattern speed $33\; {\rm km}\;{\rm s}^{-1}\;{\rm kpc}^{-1}$ $23\; kpc}^{-1}$. shape...
Abstract We use the timescale distribution of ∼3000 microlensing events measured by OGLE-III survey, together with accurate new made-to-measure dynamical models Galactic bulge/bar region, to measure IMF in inner Milky Way. The each event depends on mass lensing object, relative distances and velocities lens source. model statistically provides these velocities, allowing us constrain function, thereby infer IMF. Parameterizing as a broken power-law, we find slopes main-sequence , brown dwarf...
The Andromeda galaxy (M31) contains a box/peanut bulge (BPB) entangled with classical (CB) requiring triaxial modelling to determine the dynamics, stellar and dark matter mass. We construct made-to-measure models fitting new VIRUS-W IFU kinematic observations, IRAC-3.6$\mu$m photometry, disc's HI rotation curve. explore parameter space for 3.6$\mu$m mass-to-light ratio $(\Upsilon_{3.6})$, bar pattern speed ($\Omega_p$), mass in composite ($M^B_{DM}$) within 3.2kpc. Considering Einasto...
The second data release of the Gaia mission has revealed, in stellar velocity and action space, multiple ridges, exact origin which is still debated. Recently, we demonstrated that a large Galactic bar with pattern speed 39 km/s/kpc does create most observed ridges. Among those Hercules moving group would then be associated to orbits trapped at co-rotation resonance bar. Here show distinctive prediction such model angular momentum Sun's radius must significantly decrease increasing...
We investigated the relationship between kinematics and mass of young (<3 × 108 yr) white dwarfs using proper motions. Our sample is taken from colour-selected catalogues Sloan Digital Sky Survey Palomar–Green Survey, both which have spectroscopic temperature gravity determinations. find that dispersion decreases with increasing dwarf mass. This can be explained as a result less scattering by objects in Galactic disc during shorter lifetime their more massive progenitors. A direct this high...
The Hercules stream is a group of comoving stars in the solar neighbourhood, which can potentially be explained as signature either outer Lindblad resonance (OLR) fast Galactic bar or corotation (CR) slower bar. In case, feature should present over large area disc. With recent commissioning APOGEE-2 Southern spectrograph we search for at (l, b) = (270°, 0), direction stream, if caused by bar's OLR, would strong enough to detected using only line-of-sight velocities. We clearly detect narrow,...
Recently an unidentified emission line at 3.55 keV has been detected in X-ray spectra of clusters galaxies. The discussed as a possible decay signature 7.1 sterile neutrinos, which have proposed dark matter (DM) candidate. We aim to further constrain the strength and its implied mixing angle under assumption that all DM is made neutrinos. observations Limiting Window (LW) towards Galactic bulge (GB) offer unique dataset for exploring lines. characterize systematic uncertainties observation...
Andromeda is our nearest neighbouring disk galaxy and a prime target for detailed modelling of the evolutionary processes that shape galaxies. We analyse nature M31's triaxial bulge with an extensive set N-body models, which include Box/Peanut (B/P) bulges as well initial classical (ICBs). Comparing IRAC 3.6$\mu m$ data, only one model matches simultaneously all morphological properties bulge, requires ICB B/P 1/3 2/3 total mass respectively. find pure models do not show concentrations high...
We use the second Gaia data release in combination with catalog of Sanders & Das (2018) to dissect Milky Way disc phase-space and relative ages. confirm report existence multiple velocity moving groups at low azimuthal velocities angular momenta, below Arcturus, regularly separated by $\sim~18-20\,\rm{km s^{-1}}$ velocity. Such features were predicted exist more than ten years ago from reaction a perturbation undergoing phase-mixing. These structures appear slightly younger their...