A5005812567- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Astro and Planetary Science
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Astrophysics and Cosmic Phenomena
- Solar and Space Plasma Dynamics
- Simulation Techniques and Applications
- Calibration and Measurement Techniques
- Dark Matter and Cosmic Phenomena
- Cellular Automata and Applications
- Scientific Research and Discoveries
- Relativity and Gravitational Theory
- Dynamics and Control of Mechanical Systems
- Particle Accelerators and Free-Electron Lasers
- Impact of Light on Environment and Health
- Cosmology and Gravitation Theories
- Pulsars and Gravitational Waves Research
- Meteorological Phenomena and Simulations
- Fluid Dynamics and Turbulent Flows
- Maritime and Coastal Archaeology
- Geomagnetism and Paleomagnetism Studies
ARC Centre of Excellence for All-sky Astrophysics
2019-2024
ASTRO-3D
2019-2024
The University of Sydney
2015-2024
Australian National University
2021
University of Potsdam
2011-2013
University of Göttingen
2006-2007
Universitätsmedizin Göttingen
2005-2006
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 use the second data releases of ESA Gaia astrometric survey and high-resolution GALAH spectroscopic to analyse structure our Galaxy's disc components. With GALAH, we separate alpha-rich alpha-poor discs (with respect Fe), which are superposed in both position velocity space, examine their distributions action space. study distribution stars zV_z phase plane, for V_phi V_R, recover remarkable "phase spiral" discovered by Gaia. identify anticipated quadrupole signature a tilted ellipsoid...
Open clusters are unique tracers of the history our own Galaxy's disk. According to membership analysis based on \textit{Gaia} astrometry, out 226 potential falling in footprint GALAH or APOGEE, we find that 205 have secure members were observed by at least one survey. Furthermore, 134 high-quality spectroscopic data use determine their chemical composition. We leverage this information study distribution throughout Galactic disk 21 elements, from C Eu. The radial metallicity gradient...
In 2018, the ESA \Gaia\ satellite discovered a remarkable spiral pattern ("phase spiral") in $z-V_z$ phase plane throughout solar neighbourhood, where $z$ and $V_z$ are displacement velocity of star perpendicular to Galactic disc. response Binney \& Sch\"onrich's analytic model disc-crossing explain data, we carry out high-resolution, N-body simulation (N$\:\approx 10^8$ particles) an impulsive mass ($2\times 10^{10}$ \Msun) that interacts with cold stellar disc at single transit point. The...
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 $L_z$,...
Abstract Recent observations of high-redshift galactic disks ( z ≈ 1–3) show a strong negative trend in the dark-matter (DM) fraction f DM with increasing baryon surface density. For this to be true, inner baryons must dominate over early massive galaxies, as observed Milky Way today. If are dominant at times, we that stellar bars form promptly within these disks, leading high bar fraction. New James Webb Space Telescope provide best evidence for mature redshift range. The disk mass R s =...
Gaia DR2 has revealed new small-scale and large-scale patterns in the phase-space distribution of stars Milky Way. In cylindrical Galactic coordinates $(R,ϕ,z)$, ridge-like structures can be seen \vphiR{} plane asymmetric arch-like \vphivR{} plane. We show that ridges are also clearly present when third dimension is represented by $\langle z \rangle$, V_z V_R $\langle$[Fe/H]$\rangle$ $\langle[α/{\rm Fe}]\rangle$. The maps suggest along lie preferentially close to midplane ($|z|<0.2$ kpc),...
We present the most sensitive and detailed view of neutral hydrogen (HI) emission associated with Small Magellanic Cloud (SMC), through combination data from Australian Square Kilometre Array Pathfinder (ASKAP) Parkes (Murriyang), as part Galactic (GASKAP) pilot survey. These GASKAP-HI observations, for first time, reveal HI in SMC on similar physical scales other important tracers interstellar medium, such molecular gas dust. The resultant image cube possesses an rms noise level 1.1 K (1.6...
The Voigt-Hjerting function is fundamental in order to correctly model the profiles of absorption lines imprinted spectra bright background sources by intervening absorbing systems. In this work we present a simple analytic approximation context line intergalactic HI absorbers. Using basic calculus tools, derive an expression for that contains only fourth polynomial and Gaussian functions. connection with coefficient neutral hydrogen, suitable modeling Voigt accuracy $10^{-4}$ or better...
The Galactic halo contains a complex ecosystem of multiphase intermediate-velocity and high-velocity gas clouds whose origin has defied clear explanation. They are generally believed to be involved in Galaxy-wide recycling process, either through an accretion flow or large-scale fountain flow, both. We examine the evolution these light recent claims that they may trigger condensation from corona as move it. measure along cloud's wake, with without presence ambient magnetic field, using two-...
Previous studies have found that the elemental abundances of a star correlate directly with its age and metallicity. Using this knowledge, we derive ages for sample 250,000 stars taken from GALAH DR3 using only their overall metallicity chemical abundances. Stellar are estimated via machine learning algorithm $XGBoost$, main sequence turnoff precise as our input training set. We find stellar bulk accurate to 1-2 Gyr method. With these ages, replicate many recent results on age-kinematic...
Abstract The Galactic bulge is critical to our understanding of the Milky Way. However, due lack reliable stellar distances, structure and kinematics bulge/bar beyond center have remained largely unexplored. Here, we present a method measure distances luminous red giants using period–amplitude–luminosity relation anchored Large Magellanic Cloud, with random uncertainties 10%–15% systematic errors below 1%–2%. We apply this data from Optical Gravitational Lensing Experiment 190,302 stars in...
We investigate the origin and physical properties of OVI absorbers at low redshift (z = 0.25) using a subset cosmological, hydrodynamical simulations from OverWhelmingly Large Simulations (OWLS) project. Intervening are believed to trace shock-heated gas in Warm-Hot Intergalactic Medium (WHIM) may thus play key role search for missing baryons present-day Universe. When compared observations, predicted distributions different line parameters (column density, Doppler parameter, rest equivalent...
We investigate the physical state of H i absorbing gas at low redshift (z = 0.25) using a subset cosmological, hydrodynamic simulations from OverWhelmingly Large Simulations project, focusing in particular on broad () Lyα absorbers (BLAs), which are believed to originate shock‐heated warm‐hot intergalactic medium (WHIM). Our fiducial model, includes radiative cooling by heavy elements and feedback supernovae active galactic nuclei, predicts that z 0.25 nearly 60 per cent mass ends up...
Abstract Recent observations of high-redshift galaxies ( z ≲ 7) reveal that a substantial fraction have turbulent, gas-rich disks with well-ordered rotation and elevated levels star formation. In some instances, show evidence spiral arms, bar-like structures. These remarkable encouraged us to explore new class dynamically self-consistent models using our agama / Ramses hydrodynamic N -body simulation framework mimic plausible progenitor the Milky Way at high redshift. We disk gas fractions f...
The Magellanic HI Stream (~2x10^9 Msun [d/55 kpc]^2) encircling the Galaxy at a distance 'd' is arguably most important tracer of what happens to gas accreting onto disk galaxy. Recent observations reveal that Stream's mass in fact dominated (3:1) by its ionised component. Here we revisit origin mysterious H-alpha recombination emission observed along much length overly bright (~150-200 milli-Rayleigh) for known Galactic ultraviolet background (~20-40 mR / kpc]^2). In an earlier model,...
The remarkable 1994 discovery of the Sagittarius dwarf galaxy (Sgr) revealed that, together with Magellanic Clouds (MCs), there are at least three major galaxies, each a total mass order 10^10 - 10^11 solar masses, falling onto Galaxy in present epoch. Beyond Galactic radius 300 kpc, dwarfs tend to retain their gas. At roughly 50 MCs have experienced substantial gas stripping as evidenced by Stream which extends from them. Since Sgr star formation long after it fell into Galaxy, is...
ABSTRACT The Magellanic Clouds (MCs) are the most massive gas-bearing systems falling into Galaxy at present epoch. They show clear signs of interaction, manifested in particular by Stream, a spectacular gaseous wake that trails from MCs extending more than 150° across sky. Ahead is ‘Leading Arm’ usually interpreted as tidal counterpart an assumption we now call question. We revisit formation these structures first-infall scenario, including for first time Galactic model with weakly...
Using data from the GALAH survey, we explore dependence of elemental abundances on stellar age and metallicity among Galactic disc stars. We find that abundance most elements can be predicted [Fe/H] with an intrinsic scatter about 0.03 dex. discuss possible causes for existence abundance-age-metallicity relations. a stochastic chemical enrichment scheme based size Supernovae remnants, show is expected to small, 0.05 dex or even smaller if there additional mixing in ISM. Elemental trends both...
ABSTRACT The outer parts of the Milky Way’s disc are significantly out equilibrium. Using only distances and proper motions stars from Gaia’s Early Data Release 3, in range |b| &lt; 10°, 130° ℓ 230°, we show that for between around 10 $14\, \mathrm{kpc}$ Galactic centre, vertical velocity is strongly dependent on angular momentum, azimuth, position above or below plane. We further how this behaviour translates into a bimodality distribution Way disc. use an N-body model impulse-like...
ABSTRACT APOGEE and GALAH are two high resolution multi-object spectroscopic surveys that provide fundamental stellar parameters multiple elemental abundance estimates for about half a million stars in the Milky Way. Both observe different wavelength regimes use data reduction pipelines leading to significant offsets trends abundances common observed both surveys. Such systematic differences/offsets make it difficult effectively utilize them investigate Galactic spite of unique advantage...
Evidence for wave-like corrugations are well established in the Milky Way and nearby disc galaxies. These were originally detected as a displacement of interstellar medium about midplane, either terms vertical distance or velocity. Over past decade, similar patterns have emerged Way's stellar disc. We investigate how these waves triggered by passing satellite. Using high-resolution N-body/hydrodynamical simulations, we systematically study set up evolve jointly gaseous discs. find that gas...
Spiral arms play a key role in the evolution of disc galaxies, defining their morphology, star formation, chemistry, and dynamics. Among various implications, it has been observed Milky Way that distribution Gaia Data Release 3 (DR3) radial actions exhibits structures might be related to spiral arms. Our goal is investigate relationship between regions low action identified simulated discs location arms, such as suggested for Galaxy previous studies For sample 23 we modelled axisymmetric...
In response to recent observations from JWST and ALMA, we explore a new class of dynamically self-consistent models using our AGAMA/Ramses hydrodynamic N-body framework (Nexus) that mimics plausible progenitor the Milky Way over wide range disc gas fractions ($f_{\rm gas} = 0-100\%$). The high surface densities encourage vigorous star formation, which in turn couples with drive turbulence. We show this coupling through momentum recoil drives 'baryon sloshing,' i.e. random walk baryonic...
The Magellanic Stream, a gaseous tail that trails behind the Clouds, could replenish Milky Way with tremendous amount of gas if it reaches Galactic disk before evaporates into halo. To determine how Stream's properties change along its length, we have conducted an observational study H-alpha emission, other optical warm ionized tracers, toward 39 sight lines. Using Wisconsin Mapper telescope, detect emission brighter than 30 - 50 mR in 26 our This extends more 2-degree away from HI emission....