A5004242476- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Galaxies: Formation, Evolution, Phenomena
- Scientific Research and Discoveries
- Astronomical Observations and Instrumentation
- Atmospheric Ozone and Climate
- History and Developments in Astronomy
- Cosmology and Gravitation Theories
- Astrophysical Phenomena and Observations
- Dark Matter and Cosmic Phenomena
- Adaptive optics and wavefront sensing
- Astronomical and nuclear sciences
- High-pressure geophysics and materials
- Geomagnetism and Paleomagnetism Studies
- Nuclear Physics and Applications
- Diverse Scientific and Economic Studies
- Historical Astronomy and Related Studies
- Spacecraft Design and Technology
- earthquake and tectonic studies
- Data Management and Algorithms
- Nuclear physics research studies
- Space Satellite Systems and Control
Flatiron Institute
2022-2025
Flatiron Health (United States)
2022-2025
Royal Observatory
2025
University of Edinburgh
2025
Liverpool John Moores University
2019-2023
The University of Queensland
2022
Max Planck Institute for Solar System Research
2020
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...
Galactic haloes in a $\Lambda$-CDM universe are predicted to host today swarm of debris resulting from cannibalised dwarf galaxies. The chemo-dynamical information recorded their stellar populations helps elucidate nature, constraining the assembly history Galaxy. Using data APOGEE and \textit{Gaia}, we examine chemical properties various halo substructures, considering elements that sample nucleosynthetic pathways. systems studied Heracles, \textit{Gaia}-Enceladus/Sausage (GES), Helmi...
The SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey has obtained high-resolution spectra for thousands of red giant stars distributed among the massive satellite galaxies Milky Way (MW): Large and Small Magellanic Clouds (LMC/SMC), Sagittarius Dwarf (Sgr), Fornax (Fnx), now fully disrupted \emph{Gaia} Sausage/Enceladus (GSE) system. We present analyze APOGEE chemical abundance patterns each galaxy to draw robust conclusions about their star formation histories,...
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...
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 Stars that formed with an initial mass of over 50 M ⊙ are very rare today, but they thought to be more common in the early Universe. The fates those early, metal-poor, massive stars highly uncertain. Most expected directly collapse black holes, while some may explode as a result rotationally powered engines or pair-creation instability. We present chemical abundances J0931+0038, nearby low-mass star identified follow-up SDSS-V Milky Way Mapper, which preserves signature unusual...
ABSTRACT The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the ‘last major merger.’ Hypotheses for origin of this include Gaia-Sausage/Enceladus (GSE), where progenitor collided MW proto-disc 8–11 Gyr ago, and Virgo Radial Merger (VRM), disc within last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space, because morphology debris depends on how long it has had mix....
Abstract The existence of high- α stars with inferred ages <6 Gyr has been confirmed recently large spectroscopic and photometric surveys. However, stellar mergers or binary interactions can induce properties associated young ages, such as high mass, rapid rotation, activity, even in old populations. Literature studies have that at least some these apparently are merger products. none ruled out the possibility genuinely stars. Because cool GKM dwarfs spin down, rotation be used to...
ABSTRACT The spatial distribution of mono-abundance populations (MAPs, selected in [Fe/H] and [Mg/Fe]) reflect the chemical structural evolution a galaxy impose strong constraints on formation models. In this paper, we use APOGEE data to derive intrinsic density MAPs Milky Way, after carefully considering survey selection function. We find that single exponential profile is not sufficient description Way’s disc. Both individual integrated disc exhibit broken radial distribution; densities...
In the $\Lambda$-Cold Dark Matter model of Universe, galaxies form in part through accreting satellite systems. Previous work have built an understanding signatures these processes contained within galactic stellar halos. This revisits that picture using seven Milky Way-like \textit{Latte} suite FIRE-2 cosmological simulations. The resolution simulations allows a comparison contributions from satellites above M$_{*}$$\gtrsim$10$\times$$^{7}$M$_{\odot}$, enabling analysis observable...
Abstract Under the assumption of a simple and time-invariant gravitational potential, many Galactic dynamics techniques infer milky Way’s mass dark matter distributions from stellar kinematic observations. These methods typically rely on parameterized potential models Galaxy must take into account nontrivial survey selection effects, because they make use density stars in phase space. Large-scale spectroscopic surveys now supply information beyond kinematics form precise label measurements...
Abstract Stellar abundances and ages afford the means to link chemical enrichment galactic formation. In Milky Way, individual element show tight correlations with age, which vary in slope across ([Fe/H]–[ α /Fe]). Here, we step from characterizing as measures of understanding how trace properties stellar birth environment disk over time. Using measurements ∼27,000 APOGEE stars ( R = 22,500, signal-to-noise ratio > 200), build simple local linear models predict a sample elements (X Si, O,...
ABSTRACT We introduce the Sloan Digital Sky Survey (SDSS)/ Apache Point Observatory Galactic Evolution Experiment (APOGEE) value-added catalogue of globular cluster (GC) stars. The is result a critical search APOGEE Data Release 17 (DR17) for candidate members all known GCs. Candidate are assigned to various GCs on basis position in sky, proper motion, and radial velocity. contains total 7737 entries 6422 unique stars associated with 72 Full DR17 information provided, including velocities...
The contribution of dissolved globular clusters (GCs) to the stellar content Galactic halo is a key constraint on models for GC formation and destruction, mass assembly history Milky Way. Earlier results from APOGEE pointed large destroyed GCs inner halo, by as much 25$\%$, which an order magnitude larger than previous estimates more distant regions halo. We set out measure ratio between N-rich normal field stars, function distance, performing density modelling populations in DR16. Our show...
Abstract In the era of large-scale spectroscopic surveys in Local Group, we can explore using chemical abundances halo stars to study star formation and enrichment histories dwarf galaxy progenitors Milky Way (MW) M31 stellar halos. this paper, investigate abundance ratio distributions (CARDs) seven halos from Latte suite FIRE-2 simulations. We attempt infer galaxies’ assembly by modeling CARDs galaxies as a linear combination template disrupted dwarfs, with different masses M ⋆ quenching...
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 We show with Gaia XP spectroscopy that extremely metal-rich (EMR) stars in the Milky Way ([M/H] ≳ 0.5) are largely confined to a tight “knot” at center of Galaxy. This EMR knot is round projection, has fairly abrupt edge near R GC,proj ∼ 1.5 kpc, and dynamically hot system. central also contains very (VMR; +0.2 ≤ [M/H] +0.4) stars. However, contrast stars, bulk VMR forms an extended, highly flattened distribution inner Galaxy ( GC ≲ 5 kpc). draw on TNG50 simulations analogs for...
[Abbreviated] Context: Studies of the LMC's internal kinematics have provided a detailed view its structure, largely by exquisite proper motion data supplied Gaia. However, LoS velocities are only available for small subset Gaia data, limiting studies perpendicular to LMC disc plane. Aims: We synergise new SDSS-IV/V velocity measurements with increasing 5D phase-space sample almost factor three. interpret and model vertical structure disc. Methods: Split our into different stellar types....
Abstract The vertical kinematics of stars near the Sun can be used to measure total mass distribution Galactic disk and study out-of-equilibrium dynamics. With contemporary stellar surveys, tracers dynamics are so numerous well measured that shapes underlying orbits almost directly visible in data through element abundances or even density. These infer a model for Milky Way, enabling constraints on dark matter inner galaxy. Here, we present flexible foliating position–velocity phase space...
The large volume of spectroscopic data available now and from near-future surveys will enable high-dimensional measurements stellar parameters properties. Current methods for determining labels spectra use physics-driven models, which are computationally expensive have limitations in their accuracy due to simplifications. While machine learning provide efficient paths toward emulating physics-based pipelines, they often do not properly account uncertainties complex model structure, both can...
Abstract Unravelling galaxy formation theory requires understanding galaxies both at high and low redshifts. A possible way to connect realms is by studying the oldest stars in Milky Way (i.e., proto-Galaxy). We use APOGEE-Gaia surveys perform a purely chemical dissection of (MW) stellar populations, identify samples likely belonging proto-Galactic fragments. The metallicity dependence distribution old MW [Mg/Mn]-[Al/Fe] enables distinction least two populations terms their star histories:...
Abstract The inner ∼5 kiloparsec (kpc) region of the Milky Way is complex. However, unravelling evolution Galaxy requires precise understanding formation this region. We report a study focused on disentangling (r &lt; 5 kpc) using measured positions, velocities, and element abundance ratios red giant stars from APOGEE-Gaia surveys. After removing stellar halo, populations can be grouped into three main components based their angular momentum: bar, disc, previously unreported “knot”...
Abstract ΛCDM cosmology predicts the hierarchical formation of galaxies, which build up mass by merger events and accreting smaller systems. The stellar halo Milky Way (MW) has proven to be useful a tool for tracing this accretion history. However, most work focused on outer where dynamical times are large properties accreted systems preserved. In work, we investigate inner galaxy regime, relatively small generally completely phase mixed. Using FIRE-2 Auriga cosmological zoom-in simulation...
Abstract Observations of the Milky Way’s stellar halo find that it is predominantly comprised a radially biased population stars, dubbed Gaia Sausage–Enceladus, or GSE. These stars are thought to be debris from dwarf galaxy accretion early in history. Though typically considered single merger, possible GSE has multiple sources. To investigate this possibility, we use I llustris TNG50 simulation identify histories 98 Way analogs—the largest sample for which such an identification been...
Abstract We present a method to determine the gravitational potential of Milky Way from measurements locations, velocities, and element abundances stars in Galactic disk. The relies on assumption that Galaxy is axisymmetric stationary abundance ratios such as [Fe/H] [Mg/Fe] are smooth functions three isolating integrals motion. use Fisher Information theory predict efficacy individual constrain potential. also N -body simulations test extent by which secular evolution disk introduces...