A5011829237- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Adaptive optics and wavefront sensing
- Semiconductor Lasers and Optical Devices
- Optical Network Technologies
- Space Satellite Systems and Control
- Scientific Research and Discoveries
- Galaxies: Formation, Evolution, Phenomena
- Spectroscopy and Chemometric Analyses
- Education and Technology Integration
- solar cell performance optimization
- High-pressure geophysics and materials
- Pulsars and Gravitational Waves Research
- Molecular spectroscopy and chirality
- Optical Systems and Laser Technology
- Characterization and Applications of Magnetic Nanoparticles
- Advances in Cucurbitaceae Research
- Astronomical and nuclear sciences
- Nonlinear Waves and Solitons
- Calibration and Measurement Techniques
- Blind Source Separation Techniques
University of Cambridge
2022-2025
Australian National University
2018-2024
ARC Centre of Excellence for All-sky Astrophysics
2021-2023
ASTRO-3D
2021-2023
Mount Stromlo Observatory
2021-2023
ACT Government
2023
Institute of Astronomy
2023
University of Victoria
2016-2020
Australian Astronomical Observatory
2020
Spectroscopic surveys require fast and efficient analysis methods to maximize their scientific impact. Here we apply a deep neural network architecture analyze both SDSS-III APOGEE DR13 synthetic stellar spectra. When our convolutional model (StarNet) is trained on spectra, show that the parameters (temperature, gravity, metallicity) are determined with similar precision accuracy as pipeline. StarNet can also predict when data, excellent for data over wide range of signal-to-noise ratios. In...
Since the advent of $Gaia$ astrometry, it is possible to identify massive accreted systems within Galaxy through their unique dynamical signatures. One such system, $Gaia$-Sausage-Enceladus (GSE), appears be an early "building block" given its virial mass $> 10^{10}\,\mathrm{M_\odot}$ at infall ($z\sim1-3$). In order separate progenitor population from background stars, we investigate chemical properties with up 30 element abundances GALAH+ Survey Data Release 3 (DR3). To inform our choice...
ABSTRACT We employ our Bayesian Machine Learning framework BINGO (Bayesian INference for Galactic archaeOlogy) to obtain high-quality stellar age estimates 68 360 red giant and clump stars present in the 17th data release of Sloan Digital Sky Survey, APOGEE-2 high-resolution spectroscopic survey. By examining denoised age-metallicity relationship disc stars, we identify a drop metallicity with an increase [Mg/Fe] at early epoch, followed by chemical enrichment episode increasing [Fe/H]...
ABSTRACT The oldest stars in the Milky Way (born first few billion years) are expected to have a high density inner kpc, spatially overlapping with Galactic bulge. We use spectroscopic data from Pristine Inner Galaxy Survey (PIGS) study dynamical properties of ancient, metal-poor stars. compute distances using starhorse, and orbital barred potential. With this paper, we release AAT/PIGS catalogue (13 235 stars). find that most PIGS orbits typical for pressure-supported population. fraction...
We report the discovery, tracking and detection circumstances for 85 trans-Neptunian objects (TNOs) from first 42 deg$^{2}$ of Outer Solar System Origins Survey (OSSOS). This ongoing $r$-band survey uses 0.9 field-of-view MegaPrime camera on 3.6 m Canada-France-Hawaii Telescope. Our orbital elements these TNOs are precise to a fractional semi-major axis uncertainty $<0.1\%$. achieve this precision in just two oppositions, as compared normal 3-5 via dense observing cadence innovative...
The low-metallicity, kinematically interesting dwarf stars studied by Stephens \& Boesgaard (2002, SB02) are re-examined using Gaia DR2 astrometry, and updated model atmospheres atomic line data. New stellar parameters determined based on the parallactic distances Dartmouth Stellar Evolution Database isochrones. These in excellent agreement with spectroscopically for [Fe/H]$>-2$; however, large disagreements found [Fe/H]$\le-2$, offsets as $\Delta$T$_{\rm eff}\sim+500$ K...
In this work we combine spectroscopic information from the \textit{SkyMapper survey for Extremely Metal-Poor stars} and astrometry Gaia DR2 to investigate kinematics of a sample 475 stars with metallicity range $ -6.5 \leq \rm [Fe/H] -2.05$ dex. Exploiting action map, identify 16 40 dynamically consistent \textit{Gaia Sausage} Sequoia} accretion events, respectively. The most metal-poor these candidates have metallicities $\rm [Fe/H]=-3.31$ [Fe/H]=-3.74$, respectively, helping define...
ABSTRACT We combine stellar orbits with the abundances of heavy, r-process element europium and light, $\alpha$-element, silicon to separate in situ accreted populations Milky Way (MW) across all metallicities. At high orbital energy, accretion-dominated halo shows elevated values [Eu/Si], while at lower energies, where many stars were born situ, levels [Eu/Si] are lower. These systematically different MW imply that scatter [Eu/$\alpha$] within a single galaxy is smaller than previously...
Abstract Carbon-rich (C-rich) stars can be found at all metallicities and evolutionary stages. They are often the result of mass-transfer from a companion, but some most metal-poor C-rich objects likely carrying imprint metal-free First Stars birth. In this work, we employ neural network to predict carbon abundances for over 10 million with Gaia low-resolution XP spectra, down $\rm {[Fe/H]} = -3.0$ up {[C/Fe]} \approx +2$. We identify ∼2000 high-confidence bright (G &lt; 16)...
ABSTRACT M 22 (NGC 6656) is a chemically complex globular cluster-like system reported to harbour heavy element abundance variations. However, the extent of these variations and origin this cluster still debated. In work, we investigate chemical in-homogeneity using differential line-by-line analysis high-quality (R = 110 000, S/N 300 per pixel at 514 nm) VLT/UVES spectra six carefully chosen red giant branch stars. By achieving uncertainties as low ∼0.01 dex (∼2 cent), high precision data...
ABSTRACT In this work, we look for evidence of a non-unity mass ratio binary dwarf galaxy merger in the Sagittarius stream. Simulations such show that, upon merging with host, particles from less massive will often mostly be found extended stream and so central remnant. Motivated by these simulations, use Apache Point Observatory Galactic Evolution Experiment Data Release 17 chemical data approximately 1100 stars both remnant to contamination second galaxy. We separate into its compare...
ABSTRACT Detailed chemical studies of F/G/K – or solar-type stars have long been routine in stellar astrophysics, enabling both Galactic chemodynamics and exoplanet demographics. However, similar understanding the chemistry M late-K dwarfs most common Galaxy has greatly hampered observationally theoretically by complex molecular their atmospheres. Here, we present a new implementation data-driven Cannon model, modelling Teff, log g, [Fe/H], [Ti/Fe] trained on low–medium resolution optical...
The assembly history of the Milky Way (MW) is a rapidly evolving subject, with numerous small accretion events and at least one major merger proposed in MW's history. Accreted alongside these dwarf galaxies are globular clusters (GCs), which act as spatially coherent remnants past events. Using high precision differential abundance measurements from our recently published study, we investigate likelihood that MW NGC 362 288 galactic siblings, accreted part Gaia-Sausage-Enceladus (GSE)...
A consortium of several Australian and European institutes – together with the Southern Observatory (ESO) has initiated design MAVIS, a Multi-Conjugate Adaptive Optics (MCAO) system for ground- based 8-m Very Large Telescope (VLT). MAVIS (MCAO-assisted Visible Imager Spectrograph) will deliver visible images integral field spectrograph data 2-3x better angular resolution than Hubble Space Telescope, making it powerful complement at wavelengths to future facilities like space-based James Webb...
We present the Phase A Science Case for Multi-conjugate Adaptive-optics Visible Imager-Spectrograph (MAVIS), planned Adaptive Optics Facility (AOF) of Very Large Telescope (VLT). MAVIS is a general-purpose instrument exploiting highest possible angular resolution any single optical telescope available in next decade, either on Earth or space, and with sensitivity comparable to (or better than) larger aperture facilities. uses two deformable mirrors addition secondary mirror AOF, providing...
The view of globular clusters (GCs) as simple systems continues to unravel, revealing complex objects hosting multiple chemical peculiarities. Using differential abundance analysis, we probe the chemistry Type I GC, NGC 288 and II 362 at 2\% level for first time. We measure 20 elements find measurement uncertainties on order 0.01-0.02 dex in both clusters. smallest are measured Fe clusters, with an average uncertainty $\sim$0.013 dex. Dispersion abundances Na, Al, Ti I, Ni, Y, Zr, Ba Nd...
Abstract We search for globular clusters (GCs) trapped in resonances with the bar of Milky Way (MW). By integrating their orbits a potential decelerating bar, we select 10 whose are significantly changed by its presence. Most these corotation resonance, including M22 and 47 Tuc. The is capable transporting GCs to current positions from much lower energies, angular momenta, radii. Our results indicate that likely have reshaped MW’s GC system via resonances. also discuss implications origins...
Globular clusters (GCs) are sites of extremely efficient star formation, and recent studies suggest they significantly contributed to the early Milky Way's stellar mass build-up. Although their role has since diminished, GCs' impact on Galaxy's initial evolution can be traced today by identifying most chemically unique stars--those with anomalous nitrogen aluminum overabundances oxygen depletion. While a perfect tracer clusters, it intact or fully dissolved, these high-[N/O], high-[Al/Fe]...
The Maunakea Spectroscopic Explorer (MSE) is a next-generation observatory, designed to provide highly multiplexed, multi-object spectroscopy over wide field of view. observatory will consist (1) telescope with an 11.25 m aperture, (2) 1.5 square-degree science view, (3) fibre optic positioning and transmission systems, (4) suite low (R=3000), moderate (R=6000) high resolution (R=40,000) spectrographs. Fibre Transmission System (FiTS) consists 4332 optical fibres, transmit the light from...
In the past few years, there has been a resurgence in studies of space-based optical/infrared interferometry, particularly with vision to use technique discover and characterize temperate Earth-like exoplanets around solar analogs. One key technological leaps needed make such mission feasible is demonstrating that formation flying precision at level for interferometry possible. Here, we present Pyxis, ground-based demonstrator future small satellite aim demonstrate metrology interferometry....
(Abridged) This is the Maunakea Spectroscopic Explorer 2018 book. It intended as a concise reference guide to all aspects of scientific and technical design MSE, for international astronomy engineering communities, related agencies. The current version status report MSE's science goals their practical implementation, following System Conceptual Design Review, held in January 2018. MSE planned 10-m class, wide-field, optical near-infrared facility, designed enable transformative science,...
Accurate astrometry is a key deliverable for the next generation of multi-conjugate adaptive optics (MCAO) systems. The MCAO Visible Imager and Spectrograph (MAVIS) being designed Very Large Telescope Adaptive Optics Facility must achieve 150 $μ$as astrometric precision (50 goal). To test this before going on-sky, we have created MAVISIM, tool to simulate MAVIS images. MAVISIM accounts three major sources error, high- low-order point spread function (PSF) spatial variability, tip-tilt...
ABSTRACT In this work, we combine information from solar-like oscillations, high-resolution spectroscopy, and Gaia astrometry to derive stellar ages, chemical abundances, kinematics for a group of seven metal-poor red giants characterize them in multidimensional chrono-chemo-dynamical space. Chemical abundance ratios were derived through classical spectroscopic analysis employing 1D LTE atmospheres on Keck/HIRES spectra. Stellar masses, radii calculated with grid-based modelling, taking...
Abstract We present the first results from GeMS/GSAOI Galactic Globular Cluster Survey (G4CS) of Milky Way globular clusters NGC 3201 and 2298. Using Gemini South Adaptive Optics Imager (GSAOI), in tandem with Multi-conjugate adaptive optics System (GeMS) on 8.1 m Gemini-South telescope, we collected deep near-IR observations both clusters, resolving their constituent stellar populations down to K s ≃ 21 Vega mag. Point-spread function (PSF) photometry was performed data using spatially...