A5085763615- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Geophysics and Gravity Measurements
- History and Developments in Astronomy
- Advanced Vision and Imaging
- Adaptive optics and wavefront sensing
- Remote Sensing in Agriculture
- Space Science and Extraterrestrial Life
- Advanced Measurement and Metrology Techniques
- Phase Equilibria and Thermodynamics
- Distributed and Parallel Computing Systems
- Medical Imaging Techniques and Applications
- Computational Physics and Python Applications
- Particle Detector Development and Performance
- Fractal and DNA sequence analysis
- Data Visualization and Analytics
- Advanced Statistical Methods and Models
- Satellite Image Processing and Photogrammetry
- CCD and CMOS Imaging Sensors
Liverpool John Moores University
2014-2024
Max Planck Institute for Astronomy
2014-2019
Union astronomique internationale
2017
Centre for Astrophysics of the University of Porto
2017
Swinburne University of Technology
2012-2015
Max Planck Society
2014-2015
CEA Paris-Saclay
2010
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2008-2010
Astrophysique, Instrumentation et Modélisation
2008-2010
Université Paris Cité
2008-2010
We point out a natural mechanism for quenching of star formation in early-type galaxies. It automatically links the color galaxy with its morphology and does not require gas consumption, removal or termination supply. Given that takes place gravitationally unstable disks, it can be quenched when disk becomes stable against fragmentation to bound clumps. This result from growth stellar spheroid, instance by mergers. present concept morphological (MQ) using standard instability analysis,...
The formation of thick stellar disks in spiral galaxies is studied. Simulations gas-rich young show internal clumps by gravitational instabilities, clump coalescence into a bulge, and disk thickening strong scattering. bulge modern may form this way. minor mergers make too, but there an important difference. Thick made processes have constant scale height with galactocentric radius, flare. difference arises because the first case, perpendicular forcing disk-gravity resistance are both...
In the first paper of this series, we present a new approach for studying chemo-dynamical evolution in disk galaxies, which consists fusing chemical models with compatible numerical simulations galactic disks. This method avoids known star formation and enrichment problems encountered simulations. Here focus on Milky Way, by using detailed thin-disk model (matching local observables, are weakly affected radial migration) simulation cosmological context, dynamical properties close to those...
[Abridge] In the first paper of this series (paper I) we presented a new approach for studying chemo-odynamical evolution in disk galaxies, focusing on Milky Way. Here extend these results to different distances from Galactic center, looking variations observables that can be related on-going and future spectroscopic surveys. By separating effects kinematic heating radial migration, show migration is much more important, even oldest hottest stellar population. The distributions birth guiding...
We show that the masses of red giant stars can be well predicted from their photospheric carbon and nitrogen abundances, in conjunction with spectroscopic stellar labels log g, Teff, [Fe/H]. This is qualitatively expected mass-dependent post-main-sequence evolution. here establish an empirical relation between these quantities by drawing on 1475 giants asteroseismic mass estimates Kepler also have Apache Point Observatory Galactic Evolution Experiment (APOGEE) DR12. assess accuracy our...
The mass of a star is arguably its most fundamental parameter. For red giant stars, tracers luminous enough to be observed across the Galaxy, implies stellar evolution age. It has proven extremely difficult infer ages and masses directly from spectra using existing methods. From KEPLER APOGEE surveys, samples several thousand stars exist with high-quality asteroseismic masses. Here we show that these data can build data-driven spectral model Cannon, which determine $\sim$ 0.07 dex DR12...
Abstract The kinematics of the Milky Way disc as a function age are well measured at solar radius, but have not been studied over wider range Galactocentric radii. Here, we measure mono-age, mono-[Fe/H] populations in low and high [α/Fe] discs between 4 ≲ R 13 kpc |z| 2 using 65 719 stars common APOGEE DR14 Gaia DR2 for which estimate ages Bayesian neural network model trained on asteroseismic ages. We determine vertical radial velocity dispersions, finding that display markedly different...
We investigate the intensity enhancement and duration of starburst episodes triggered by major galaxy interactions mergers. analyze two large statistical datasets numerical simulations. These have been obtained using independent different techniques to model baryonic dark matter evolution that are extensively compared for first time. One is a Tree-SPH code, other one grid-based N-body sticky-particles code. show that, at low redshift, mergers in general trigger only moderate star formation...
We report the discovery of a group apparently young CoRoT red-giant stars exhibiting enhanced [alpha/Fe] abundance ratios (as determined from APOGEE spectra) with respect to Solar values. Their existence is not explained by standard chemical evolution models Milky Way, and shows that chemical-enrichment history Galactic disc more complex. find similar in previously published samples for which isochrone-ages could be robustly obtained, although smaller relative numbers, explain why these have...
We derive age constraints for 1639 red giants in the APOKASC sample which seismic parameters from Kepler, as well effective temperatures, metallicities and [α/Fe] values APOGEE DR12 (Apache Point Observatory Galactic Evolution Experiment Data Release 12) are available. investigate relation between chemical abundances these stars, using a simple robust approach to obtain ages. first stellar masses standard scaling relations, then determine maximum possible each star function of its mass...
Investigations of the origin and evolution Milky Way disk have long relied on chemical kinematic identification its components to reconstruct our Galactic past. Difficulties in determining precise stellar ages restricted most studies small samples, normally confined solar neighbourhood. Here we break this impasse with help asteroseismic inference perform a chronology throughout age Galaxy. We chemically dissect population using sample red giant stars spanning out 2~kpc annulus observed by...
We determine the intrinsic, 3-dimensional shape distribution of star-forming galaxies at 0<z<2.5, as inferred from their observed projected axis ratios. In present-day universe all masses 1e9 - 1e11 Msol are predominantly thin, nearly oblate disks, in line with previous studies. now extend this to higher redshifts, and find that among massive (M* > 1e10 Msol) disks most common geometric z < 2. Lower-mass z>1 possess a broad range shapes: fraction elongated (prolate) increases toward...
We present a semi-empirical, largely model-independent approach for estimating Galactic birth radii, r_birth, Milky Way disk stars. The technique relies on the justifiable assumption that negative radial metallicity gradient in interstellar medium (ISM) existed most of lifetime. Stars are projected back to their positions according observationally derived age and [Fe/H] with no kinematical information required. Applying our AMBRE:HARPS HARPS-GTO local samples, we show can constrain ISM...
We study the evolution of galactic bars and link with disk spheroid formation in a sample zoom-in cosmological simulations. Our simulation focuses on galaxies present-day stellar masses 10^10-10^11 Msun range, field loose group environments, broad variety mass growth histories. In our models, are almost absent from progenitors spirals at z>1.5, they remain rare generally too weak to be observable down z~1. After this characteristic epoch, fractions strong raise rapidly, being present 80%...
Non-axisymmetric components, such as spirals and central bars, play a major role in shaping galactic discs. An important aspect of the disc secular evolution driven by these perturbers is radial migration stars. It has been suggested recently that can populate thick-disc component from inner-disc stars with high vertical energies. Since this never demonstrated simulations, we study detail effect on velocity dispersion thickness, separating simulated into migrators non-migrators. We apply...
We have undertaken an ambitious program to visually classify all galaxies in the five CANDELS fields down H<24.5 involving dedicated efforts of 65 individual classifiers. Once completed, we expect detailed morphological classifications for over 50,000 up z<4 fields. Here, present our visual classification scheme, which was designed cover a wide range science goals. This scheme includes basic Hubble sequence types, but also look at mergers and interactions, clumpiness galaxies,...
We analyze a suite of 33 cosmological simulations the evolution Milky Way-mass galaxies in low-density environments. Our sample spans broad range Hubble types at z=0, from nearly bulgeless disks to bulge-dominated galaxies. Despite fact that large fraction bulge is typically place by z=1, we find no significant correlation between morphology z=1 and z=0. The progenitors disk span morphologies, including smooth disks, unstable interacting systems. By z=0.5, spiral arms bars are largely...
Recent spectroscopic observations in the Milky Way suggest that chemically defined thick disk (stars have high [α/Fe] ratios and are thus old) has a significantly smaller scale-length than thin disk. This is apparent contradiction with of external edge-on galaxies, where components comparable scale-lengths. Moreover, while observed disks do not flare (scale-height does increase radius), numerical simulations flaring unavoidable, resulting from both environmental effects secular evolution....
With the advent of space missions CoRoT and Kepler, it has become feasible to determine precise asteroseismic masses ages for large samples red-giant stars. In this paper, we present CoRoGEE dataset -- obtained from lightcurves 606 red giant stars in two fields Galactic disc which have been co-observed an ancillary project APOGEE. We used Bayesian parameter estimation code PARAM calculate distances, extinctions, masses, these a homogeneous analysis, resulting relative statistical...
We study the global efficiency of star formation in high resolution hydrodynamical simulations gas discs embedded isolated early-type and spiral galaxies. Despite using a universal local law to form stars simulations, we find that galaxies are offset from spirals on large-scale Kennicutt relation, 2 5 times less efficiently. This is agreement with previous results morphological quenching: more stable against when due lower disc self-gravity increased shear. As result, these do not fragment...
We study the relation between stellar ages and vertical velocity dispersion (the age–velocity relation, or AVR) in a sample of seven simulated disc galaxies. In our simulations, shape AVR for stars younger than 9 Gyr depends strongly on merger history at low redshift, with even 1:10–1:15 mergers being able to create jumps (although these might not be detectable if errors are order 30 per cent). For galaxies quiescent we find that rises smoothly up 8–9 Gyr, following power law slope ∼0.5,...
Deciphering the assembly history of Milky Way is a formidable task, which becomes possible only if one can produce high-resolution chrono-chemo-kinematical maps Galaxy. Data from large-scale astrometric and spectroscopic surveys will soon provide us with well-defined view current chemo-kinematical structure Way, but enable blurred on temporal sequence that led to present-day As demonstrated by (ongoing) exploitation data pioneering photometric missions CoRoT, Kepler, K2, asteroseismology...
The Time Inference with MUSE in Extragalactic Rings (TIMER) project is a survey the VLT-MUSE integral-field spectrograph of 24 nearby barred galaxies prominent central structures (e.g., nuclear rings or inner discs). main goals are: (i) estimating cosmic epoch when discs settle, leading to formation bars; (ii) testing hypothesis whereby more massive are assembled first; and (iii) characterising history external gas accretion disc galaxies. We present details on sample selection,...