David M. Nataf
A5079969384- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Adaptive optics and wavefront sensing
- Galaxies: Formation, Evolution, Phenomena
- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Geophysics and Gravity Measurements
- Astronomical and nuclear sciences
- History and Developments in Astronomy
- Calibration and Measurement Techniques
- Solar and Space Plasma Dynamics
- Atmospheric Ozone and Climate
- Space Exploration and Technology
- Research Data Management Practices
- Spectroscopy and Chemometric Analyses
- Computational Physics and Python Applications
- Scientific Measurement and Uncertainty Evaluation
- Optical Coherence Tomography Applications
- Historical and Architectural Studies
- High-pressure geophysics and materials
Johns Hopkins University
2017-2024
Australian National University
2013-2021
Virginia Tech
2021
Kavli Institute for the Physics and Mathematics of the Universe
2021
The University of Tokyo
2021
University of Amsterdam
2021
Max Planck Institute for Astronomy
2019
Max Planck Society
2019
Mount Stromlo Observatory
2016
The Ohio State University
2010-2015
The GALAH survey is a large high-resolution spectroscopic using the newly commissioned HERMES spectrograph on Anglo-Australian Telescope. provides (R ~28,000) spectra in four passbands for 392 stars simultaneously over 2 degree field of view. goal to unravel formation and evolutionary history Milky Way, fossil remnants ancient star events which have been disrupted are now dispersed throughout Galaxy. Chemical tagging seeks identify such solely from their common unique chemical signatures;...
The ensemble of chemical element abundance measurements for stars, along with precision distances and orbit properties, provides high-dimensional data to study the evolution Milky Way. With this third release Galactic Archaeology HERMES (GALAH) survey, we publish 678 423 spectra 588 571 mostly nearby stars (81.2% are within <2 kpc), observed spectrograph at Anglo-Australian Telescope. This (hereafter GALAH+ DR3) includes all observations from GALAH Phase 1 (bright, main, faint 70%),...
We combine VI photometry from OGLE-III with VVV and 2MASS measurements of E(J-K_{s}) to resolve the longstanding problem non-standard optical extinction toward Galactic bulge. show that is well-fit by relation A_{I} = 0.7465*E(V-I) + 1.3700*E(J-K_{s}), or, equivalently, 1.217*E(V-I)(1+1.126*(E(J-K_{s})/E(V-I)-0.3433)). The near-IR reddening law inner Galaxy approximately follows an R_{V} \approx 2.5 curve a dispersion {\sigma}_{R_{V}} 0.2, consistent extragalactic investigations hosts type...
The Galactic Archaeology with HERMES (GALAH) survey is a large-scale stellar spectroscopic of the Milky Way and designed to deliver chemical information complementary large number stars covered by $Gaia$ mission. We present GALAH second public data release (GALAH DR2) containing 342,682 stars. For these stars, collaboration provides parameters abundances for up 23 elements community. Here we target selection, observation, reduction detailed explanation how spectra were analysed estimate...
The Galactic Archaeology with HERMES (GALAH) Survey is a massive observational project to trace the Milky Way's history of star formation, chemical enrichment, stellar migration and minor mergers. Using high-resolution (R$\simeq$28,000) spectra taken High Efficiency Resolution Multi-Element Spectrograph (HERMES) instrument at Anglo-Australian Telescope (AAT), GALAH will determine parameters abundances up 29 elements for one million stars. Selecting targets from colour-unbiased catalogue...
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....
ABSTRACT We report evidence from APOGEE for the presence of a new metal-poor stellar structure located within ∼4 kpc Galactic Centre. Characterized by chemical composition resembling those low-mass satellites Milky Way, this inner Galaxy (IGS) seems to be chemically and dynamically detached more metal-rich populations in Galaxy. conjecture that is associated with an accretion event likely occurred early life Way. Comparing mean elemental abundances predictions cosmological numerical...
The red clump is found to be split into two components along several sightlines toward the Galactic Bulge. This detected with high significance areas (-3.5<l<1,b<-5) and (l,b)=(0,+5.2), i.e., Bulge minor axis at least 5 degrees off plane. fainter (hereafter ``main'') component one that more closely follows distance-longitude relation of clump. main ~0.5 magnitudes than secondary an overall approximately equal population. For further from plane, difference in brightness increases, stars are...
ABSTRACT We investigate the Fe, C, N, O, Mg, Al, Si, K, Ca, Ce, and Nd abundances of 2283 red giant stars in 31 globular clusters from high-resolution spectra observed both Northern Southern hemisphere by SDSS-IV APOGEE-2 survey. This unprecedented homogeneous data set, largest to date, allows us discuss intrinsic Fe spread, shape, statistics Al-Mg N-C anti-correlations as a function cluster mass, luminosity, age, metallicity for all clusters. find that spread does not depend on these...
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...
We present a study of the luminosity density distribution Galactic bar using number counts red clump giants (RCGs) from OGLE-III survey. The data were recently published by Nataf et al. (2013) for 9019 fields towards bulge and have $2.94\times 10^6$ RC stars over viewing area $90.25 \,\textrm{deg}^2$. include counts, mean distance modulus ($\mu$), dispersion in $\mu$ full error matrix, which we fit with several tri-axial parametric models. use Markov Chain Monte Carlo (MCMC) method to...
Space-based microlens parallax measurements are a powerful tool for understanding planet populations, especially their distribution throughout the Galaxy. However, if space-based observations of microlensing events must be specifically targeted, it is crucial that enter sample without reference to known presence or absence planets. Hence, vital define objective criteria selecting where possible and carefully consider minimize selection biases not so final represents controlled experiment. We...
ABSTRACT We present 947 radial velocities of RR Lyrae variable stars in four fields located toward the Galactic bulge, observed within data from ongoing Bulge Radial Velocity Assay (BRAVA-RR). show that these (RRLs) exhibit hot kinematics and null or negligible rotation are therefore members a separate population bar/pseudobulge currently dominates mass luminosity inner Galaxy. Our RRLs predate structures have metallicities, kinematics, spatial distribution consistent with “classical”...
Studies of the kinematics and chemical compositions Galactic globular clusters (GCs) enable reconstruction history star formation, evolution, mass assembly Galaxy. Using latest data release (DR16) SDSS/APOGEE survey, we identify 3,090 stars associated with 46 GCs. a previously defined kinematic association, break sample down into eight separate groups examine how kinematics-based classification maps composition space, considering only $\alpha$ (mostly Si Mg) elements Fe. Our results show...
We explore the fundamental relations governing radial and vertical velocity dispersions of stars in Milky Way, from combined studies complementary surveys including GALAH, LAMOST, APOGEE, NASA $Kepler$ K2 missions, $Gaia$ DR2. find that different stellar samples, even though they target tracer populations employ a variety age estimation techniques, follow same set relations. provide clearest evidence to date that, addition well-known dependence on age, depend orbital angular momentum $L_z$,...
Cosmological models predict the oldest stars in Galaxy should be found closest to centre of potential well, bulge. The EMBLA Survey successfully searched for these old, metal-poor by making use distinctive SkyMapper photometric filters discover candidate Their nature was then confirmed using AAOmega spectrograph on AAT. Here we present an abundance analysis 10 bulge with -2.8<[Fe/H]<-1.7 from MIKE/Magellan observations, total determining abundances 22 elements. Combining results our previous...
The presence of two stellar populations in the Milky Way bulge has been reported recently. We aim at studying abundances and kinematics stars outer bulge, thereby providing additional constraints on models its formation. Spectra 401 red giant a field (l,b)=(0{\deg},-10{\deg}) were obtained with FLAMES VLT. Stars luminosities down to below clumps (RCs) are included. From these spectra we measure general metallicities, Fe alpha-elements, radial velocities (RV) stars. These measurements as well...
We present the broadest and most precise empirical investigation of red giant branch bump (RGBB) brightness number counts ever conducted. implement a new method use data from two Hubble Space Telescope globular cluster (GC) surveys to measure star RGBB in 72 GCs. The median measurement precision is 0.018 mag 31% counts, respectively, reaching peak values 0.005 10%. position main-sequence turnoff horizontal stars are used as comparisons where appropriate. Several independent scientific...
We present the data reduction procedures being used by GALAH survey, carried out with HERMES fibre-fed, multi-object spectrograph on 3.9~m Anglo-Australian Telescope. is a unique targeting 1 million stars brighter than magnitude V=14 at resolution of 28,000 goal to measure abundances 29 elements. Such large number high spectra necessitates development pipeline optimized for speed, accuracy, and consistency. outline design structure Iraf-based that we developed, specifically GALAH, produce...
Galah is an ongoing high-resolution spectroscopic survey with the goal of disentangling formation history Milky Way, using fossil remnants disrupted star sites which are now dispersed around Galaxy. It targeting a randomly selected, magnitude limited ($V \leq 14$) sample stars, observing one million objects. To date, 300,000 spectra have been obtained. Not all them correctly processed by parameter estimation pipelines and we need to know about them. We present semi-automated classification...
Asteroseismology is a promising tool to study Galactic structure and evolution because it can probe the ages of stars. Earlier attempts comparing seismic data from {\it Kepler} satellite with predictions Galaxy models found that predicted more low-mass stars compared observed distribution masses. It was unclear if mismatch due inaccuracies in models, or unknown aspects selection function Using new K2 mission, which has well-defined function, we find an old metal-poor thick disc, as used...
The overlap between the spectroscopic Galactic Archaeology with HERMES (GALAH) survey & $Gaia$ provides a high-dimensional chemodynamical space of unprecedented size. We present first analysis subset this overlap, 7066 dwarf, turn-off, sub-giant stars. [...] investigate correlations chemical compositions, ages, kinematics for sample. Stellar parameters elemental abundances are derived from GALAH spectra spectral synthesis code SME. report Li, C, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr,...
Abstract We compare abundance ratio trends in a sample of ∼11,000 Milky Way bulge stars ( R GC < 3 kpc) from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) to those APOGEE disk (5 kpc 11 kpc). divide each into low-Ia (high-[Mg/Fe]) and high-Ia (low-[Mg/Fe]) populations, population, we examine median [X/Mg] versus [Mg/H] for elements X = Fe, O, Na, Al, Si, P, S, K, Ca, V, Cr, Mn, Co, Ni, Cu, Ce. To remove small systematic abundances with stellar <?CDATA...
Microlensing detections of cool planets are important for the construction an unbiased sample to estimate frequency beyond snow line, which is where giant thought form according core accretion theory planet formation. In this paper, we report discovery a detected from analysis light curve high-magnification microlensing event MOA 2010-BLG-477. The measured planet–star mass ratio q = (2.181 ± 0.004) × 10−3 and projected separation s 1.1228 0.0006 in units Einstein radius. angular radius...