A5062301655- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Cosmology and Gravitation Theories
- Pulsars and Gravitational Waves Research
- Astronomical Observations and Instrumentation
- High-Energy Particle Collisions Research
- Scientific Research and Discoveries
- Solar and Space Plasma Dynamics
- Quantum Chromodynamics and Particle Interactions
- Astrophysics and Cosmic Phenomena
- High-pressure geophysics and materials
- Astrophysical Phenomena and Observations
- Calibration and Measurement Techniques
- Radio Astronomy Observations and Technology
- Data Analysis with R
- Spectroscopy and Chemometric Analyses
Leibniz Institute for Astrophysics Potsdam
2006-2023
Laboratoire d’Astrophysique de Marseille
2009-2010
Château Gombert
2010
Combining the precise parallaxes and optical photometry delivered by Gaia's second data release (Gaia DR2) with photometric catalogues of PanSTARRS-1, 2MASS, AllWISE, we derive Bayesian stellar parameters, distances, extinctions for 265 million stars brighter than G=18. Because wide wavelength range used, our results substantially improve accuracy precision previous extinction effective temperature estimates. After cleaning both unreliable input output data, retain 137 stars, which achieve a...
We combine high-resolution spectroscopic data from APOGEE-2 Survey Data Release 16 (DR16) with broad-band photometric several sources, as well parallaxes {\it Gaia} 2 (DR2). Using the Bayesian isochrone-fitting code {\tt StarHorse}, we derive distances, extinctions and astrophysical parameters for around 388,815 APOGEE stars, achieving typical distance uncertainties of $\sim 6\%$ giants, 2\%$ dwarfs, extinction 0.07$ mag when all information is available, 0.17$ if optical photometry missing....
We present a catalogue of 362 million stellar parameters, distances, and extinctions derived from Gaia's early third data release (EDR3) cross-matched with the photometric catalogues Pan-STARRS1, SkyMapper, 2MASS, AllWISE. The higher precision Gaia EDR3 data, combined broad wavelength coverage additional surveys new stellar-density priors {\tt StarHorse} code allow us to substantially improve accuracy over previous photo-astrometric stellar-parameter estimates. At magnitude $G=14\, (17)$,...
We investigate the inner regions of Milky Way with a sample unprecedented size and coverage thanks to APOGEE DR16 Gaia EDR3 data. Our Galactic has more than 26,000 stars within $|X_{\rm Gal}| <5$ kpc, $|Y_{\rm <3.5$ $|Z_{\rm <1$ we also make analysis for foreground-cleaned sub-sample 8,000 representative bulge-bar populations. The Galaxy shows clear chemical discontinuity in key abundance ratios [$\alpha$/Fe], [C/N], [Mn/O], probing different enrichment timescales, which suggests star...
We present the Hestia simulation suite: High-resolutions Environmental Simulations of The Immediate Area, a set cosmological simulations Local Group. Initial conditions constrained by observed peculiar velocity nearby galaxies are employed to accurately simulate local cosmography. Halo pairs that resemble Group found in low resolutions constrained, dark matter only simulations, and selected for higher resolution magneto hydrodynamic using Arepo code. Baryonic physics follows Auriga model...
Over the last few years, many studies have found an empirical relationship between abundance of a star and its age. Here we estimate spectroscopic stellar ages for 178 825 red-giant stars observed by APOGEE survey with median statistical uncertainty 17%. To this end, use supervised machine learning technique XGBoost , trained on high-quality dataset 3060 red-clump asteroseismic both Kepler . After verifying obtained age estimates independent catalogues, investigate some classical chemical,...
We have used GADGET2 to simulate the formation of an elliptical galaxy in a cosmological dark matter halo with mass 3x10^12M_Sun/h. Using stellar population synthesis model has allowed us compute magnitudes, colours and surface brightness profiles. included follow growth central black hole we compared results simulations without feedback from AGNs. studied interplay between cold gas accretion merging development galactic morphologies, link colour morphology evolution, effect AGN on...
Context. Bar formation and merger events can contribute to the rearrangement of stars within Galaxy in addition triggering star (SF) epochs. Super-metal-rich (SMR) found solar neighbourhood (SNd) be used as tracers such they are expected originate only inner have definitely migrated. Aims. We study a homogeneous large sample SMR SNd provide tighter constraints on epoch bar its impact Milky Way (MW) disc stellar populations. Methods. investigated 169 701 main sequence turnoff (MSTO) subgiant...
Context. JWST recently detected numerous disc galaxies at high redshifts, and there have been observations of cold z > 4 with ALMA. In the Milky Way (MW), recent studies highlight presence metal-poor stars in cold-disc orbits, suggesting an ancient disc. This prompts two fundamental questions. The first refers to time formation MW disc, second whether it originated as thin or larger velocity dispersion thick Aims. We carried out a chrono-chemo-dynamical study large sample precise stellar...
We show by means of a high-resolution N-body simulation how the mass assembly histories galaxy-size cold dark matter (CDM) halos depend on environment. Halos in high density environments form earlier and higher fraction their is assembled major mergers, compared to low environments. The distribution present-day specific aggregation rate strongly dependent While only ~20% are not accreting at present epoch, this rises ~80% densities. At z=1 median ~4 times larger than z=0 almost independent...
We investigate the origin and evolution of fossil groups in a concordance ΛCDM cosmological simulation. consider haloes with masses between 1 × 1013 5 1013h−1M⊙, study physical mechanisms that lead to formation large gap magnitude brightest second most bright group member, which is typical for these systems. Fossil are found have high dark matter concentrations, we can relate their early time. The gaps arise after built up half final mass, due merging massive members. show existence systems...
The solar neighborhood contains disc stars that have recently crossed spiral arms in the Galaxy. We propose boundaries local velocity distributions separate or been perturbed by a particular arm from those haven't. Ridges stellar constructed second Gaia data release trace orbits could touched nearby at apocentre pericentre. multiple ridges and arcs seen are consistent with presence of features different pattern speeds imply outer Galaxy is flocculent rather than grand design.
We use Gaia DR2 astrometric and line-of-sight velocity information combined with two sets of distances obtained a Bayesian inference method to study the 3D distribution in Milky Way disc. search for variations all Galactocentric cylindrical components ($V_{\phi}$, $V_R$ $V_z$) Galactic radius, azimuth, distance from disc mid-plane. confirm recent work showing that bulk vertical motions $R\text{-}z$ plane are consistent combination breathing bending modes. In $x\text{-}y$ plane, we show that,...
We present a cosmography analysis of the Local Universe based on recently released Two-Micron All-Sky Redshift Survey (2MRS). Our method is Bayesian Networks Machine Learning algorithm (the Kigen-code) which self-consistently samples initial density fluctuations compatible with observed galaxy distribution and structure formation model given by second order Lagrangian perturbation theory (2LPT). From conditions we obtain an ensemble reconstructed peculiar velocity fields characterize local...
Stellar activity and rotation are tightly related in a dynamo process. Our understanding of this mechanism is mainly limited by our capability inferring the properties stellar turbulent convection. In particular, convective turnover time key ingredient through estimation Rossby number, which ratio period time. work we propose new calibration $(B-V)$ color index dependence time, hence number. based on structure inferred detailed modeling solar-like pulsators using asteroseismic observables....
JWST has recently detected numerous disc galaxies at high-redshifts and there have been observations of cold z > 4 with ALMA. In the Milky Way, recent studies find metal-poor stars in orbits, suggesting an ancient disc. We investigated a sample 565,606 from hybrid-CNN analysis Gaia-DR3 RVS stars. The contains 8,500 [Fe/H]<-1. For subset ~200,000 main sequence turnoff subgiant we computed distances ages using StarHorse code mean precision 1% 12%, respectively. First, confirm existence thin...
With Gaia Data Release 3 (DR3), new and improved astrometric, photometric, spectroscopic measurements for 1.8 billion stars have become available. Alongside this wealth of data, however, there are challenges in finding efficient accurate computational methods their analysis. In paper, we explore the feasibility using machine learning regression as a method extracting basic stellar parameters line-of-sight extinctions from spectro-photometric data. To end, built stable gradient-boosted...
Over the last few years, many studies have found an empirical relationship between abundance of a star and its age. Here we estimate spectroscopic stellar ages for 178 825 red-giant stars observed by APOGEE survey with median statistical uncertainty 17%. To this end, use supervised machine learning technique XGBoost, trained on high-quality dataset 3060 red-clump asteroseismic both Kepler. After verifying obtained age estimates independent catalogues, investigate some classical chemical,...
We explore the feasibility of using machine-learning regression as a method extracting basic stellar parameters and line-of-sight extinctions, given spectro-photometric data. To this end, we build stable gradient-boosted random-forest regressor (xgboost), trained on spectroscopic data, capable producing output with reliable uncertainties from Gaia DR3 data (most notably low-resolution XP spectra) without ground-based observations. Using Shapley additive explanations, are able to interpret...
We discuss the rest-frame UV emission between 5< z < 7 from MareNostrum High-z Universe, a SPH simulation done with more than 2 billion particles. Cosmological simulations of galaxy formation generally overpredict restframe luminosity function at high redshift, both bright and faint ends. In this Letter we explore dust attenuation model where larger extinction is applied to star populations younger given age, mimicking effect clumpy interstellar medium. show that scenario fits...
In the context of large spectroscopic surveys stars, data-driven methods are key in deducing physical parameters for millions spectra a short time. Convolutional neural networks (CNNs) enable us to connect observables (e.g. spectra, stellar magnitudes) properties (atmospheric parameters, chemical abundances, or labels general). We trained CNN, adopting atmospheric and abundances from APOGEE DR16 (resolution R=22500) data as training set labels. As input, we used parts intermediate-resolution...