A data-driven decomposition of stellar abundance vectors into four latent patterns identifies distinct contributions from core-collapse supernovae, Type Ia supernovae, and AGB stars across the Milky Way disc.
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galpy: A Python Library for Galactic Dynamics
Tool reference. 83% of classified Pith citations use this work as a method, library, or software dependency, not as a substantive claim.
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abstract
I describe the design, implementation, and usage of galpy, a Python package for galactic-dynamics calculations. At its core, galpy consists of a general framework for representing galactic potentials both in Python and in C (for accelerated computations); galpy functions, objects, and methods can generally take arbitrary combinations of these as arguments. Numerical orbit integration is supported with a variety of Runge-Kutta-type and symplectic integrators. For planar orbits, integration of the phase-space volume is also possible. galpy supports the calculation of action-angle coordinates and orbital frequencies for a given phase-space point for general spherical potentials, using state-of-the-art numerical approximations for axisymmetric potentials, and making use of a recent general approximation for any static potential. A number of different distribution functions (DFs) are also included in the current release; currently these consist of two-dimensional axisymmetric and non-axisymmetric disk DFs, a three-dimensional disk DF, and a DF framework for tidal streams. I provide several examples to illustrate the use of the code. I present a simple model for the Milky Way's gravitational potential consistent with the latest observations. I also numerically calculate the Oort functions for different tracer populations of stars and compare it to a new analytical approximation. Additionally, I characterize the response of a kinematically-warm disk to an elliptical m=2 perturbation in detail. Overall, galpy consists of about 54,000 lines, including 23,000 lines of code in the module, 11,000 lines of test code, and about 20,000 lines of documentation. The test suite covers 99.6% of the code. galpy is available at http://github.com/jobovy/galpy with extensive documentation available at http://galpy.readthedocs.org/en/latest .
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representative citing papers
Stellar streams encode the initial mass function of globular clusters, recovered as a declining power-law with slope 1.3 for streams above 1000 solar masses.
Blue straggler stars in old open clusters exhibit a Kraft break in rotation, with rapid rotators above the break and slow rotators below, indicating their envelopes behave like those of single stars.
Severe gas expulsion and expansion in a primordial star cluster, combined with a top-heavy IMF, can reproduce the high velocity dispersion and broad stream of C-19 without dark matter subhalos.
DESI-HVS1 is the first reported old, low-mass, metal-poor hypervelocity star candidate whose reconstructed orbit points to a Galactic Center origin.
Reprojects abundances of 199k stars into 4 patterns, identifying enrichment pathways with strong chemo-spatial, age, and vertical correlations plus a transition at ~6 Gyr.
Hot Jupiter occurrence in the Galactic halo is low at ~0.13% with no significant difference between in-situ and accreted populations, well below disk rates.
Blue straggler stars in old open clusters predominantly appear near the terminal-age main sequence because mass transfer from asymptotic giant branch donors enriches their cores with helium.
IY Lyr is a thick-disk RRc star with a 1.37 solar-mass companion most likely a neutron star in a 3.94-year eccentric orbit, confirmed by photometry, spectroscopy, and astrometry.
The Milky Way stellar disk shows a broken radial density profile with four components, azimuthal dependence, inner and outer flaring, and a density-metallicity bump possibly from radial migration.
The Gaia-Sausage-Enceladus merger occurred 11.2 ± 0.1 Gyr ago, coinciding with the formation of a group of globular clusters and potentially leaving ω Centauri as its remnant, while placing disk formation at z ≳ 4.
300S stellar stream exhibits three density peaks, smooth width variations, a possible 4.7 degree gap, and a kink modeled as resulting from Large Magellanic Cloud interaction across its full known footprint.
A blind 12D chemo-dynamical clustering analysis with UMAP and HDBSCAN on SDSS-V DR19 and Gaia DR3 data recovers seven known halo substructures and reports five new tightly bound candidates FO1-FO5.
A lithium chemical evolution model for the GSE galaxy matches survey data showing Spite-like and eRGB plateaus at low metallicity with a hint of reduced nova contributions.
ML regressors trained on APOGEE DR17 red giants predict C, O, Mg, Si abundances from kinematics and [Fe/H] more accurately than [Fe/H] baseline, with external validation on HARPS FGK dwarfs and reproduction of Galactic chemical evolution trends.
Phase-space density is recovered from Gaia data for M4 and disrupted streams by correcting entropy injection and minimizing stream entropy, enabling original mass inference via Liouville's theorem.
Simulations show stars at the edges of stellar streams are more likely to retain unperturbed planetary systems than stars near the stream center.
The first NIR high-resolution spectroscopy of solar analog HD115617 shows a 250 K temperature discrepancy with optical data but confirms solar composition, main-sequence status, and no chemical signature of planetary formation.
Simulations show that observed rotation in 13.5-Gyr-old alpha-rich stars constrains the Gaia-Sausage-Enceladus merger to mass ratios below 1:4, with interaction and starburst times both near 11 Gyr.
High-precision abundances and Ba isotopic ratios in TYC 6044-714-1 favor an s+r nucleosynthesis scenario over i-process models, which require implausible conditions and mismatch isotopic data.
An updated orbital frequency method shows multiple Milky Way bar lengths and pattern speeds are consistent with star data within 5 percent.
Three new planets detected via 2023 KMTNet microlensing with mass ratios log q ~ -1.9, -2.0, -2.6; overall 2023 sample of 25 planets matches prior mass-ratio distribution.
Precision timing of PSR J1738+0333 from EPTA and NANOGrav data yields the tightest strong-field constraints on Einstein-aether parameters from any single binary pulsar.
In Tombaugh 2, 32% of blue straggler stars show ultraviolet excess from hot companions consistent with recent binary mass transfer, supporting this channel over mergers in a low-density cluster.
citing papers explorer
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Milky Way Mapper decoded abundances -- I. Shared disc enrichment patterns
A data-driven decomposition of stellar abundance vectors into four latent patterns identifies distinct contributions from core-collapse supernovae, Type Ia supernovae, and AGB stars across the Milky Way disc.
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Inferring Globular Cluster Initial Mass Function from Stellar Streams
Stellar streams encode the initial mass function of globular clusters, recovered as a declining power-law with slope 1.3 for streams above 1000 solar masses.
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Blue Straggler Stars in Old Open Clusters and the Kraft Break
Blue straggler stars in old open clusters exhibit a Kraft break in rotation, with rapid rotators above the break and slow rotators below, indicating their envelopes behave like those of single stars.
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The formation of the C-19 progenitor: a primordial cluster heated by gas expulsion
Severe gas expulsion and expansion in a primordial star cluster, combined with a top-heavy IMF, can reproduce the high velocity dispersion and broad stream of C-19 without dark matter subhalos.
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An Old, Low-mass, Metal-poor Hypervelocity Star Candidate Consistent with a Galactic Center Origin
DESI-HVS1 is the first reported old, low-mass, metal-poor hypervelocity star candidate whose reconstructed orbit points to a Galactic Center origin.
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Milky Way Mapper decoded abundances -- II: From patterns to paths
Reprojects abundances of 199k stars into 4 patterns, identifying enrichment pathways with strong chemo-spatial, age, and vertical correlations plus a transition at ~6 Gyr.
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Exoplanets in ancient stellar populations: occurrence constraints and hot-Jupiter candidates in the Galactic halo
Hot Jupiter occurrence in the Galactic halo is low at ~0.13% with no significant difference between in-situ and accreted populations, well below disk rates.
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The Distribution of Blue Straggler Stars in the Color-Magnitude Diagrams of Old Open Clusters
Blue straggler stars in old open clusters predominantly appear near the terminal-age main sequence because mass transfer from asymptotic giant branch donors enriches their cores with helium.
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IY Lyr: A Thick-Disk first-overtone RR Lyrae Star with a Possible Neutron Star Companion
IY Lyr is a thick-disk RRc star with a 1.37 solar-mass companion most likely a neutron star in a 3.94-year eccentric orbit, confirmed by photometry, spectroscopy, and astrometry.
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Mapping the Milky Way with Gaia Bp/Rp spectra-IV: the broken and asymmetric density profile of the stellar disk traced by a large sample of red clumps
The Milky Way stellar disk shows a broken radial density profile with four components, azimuthal dependence, inner and outer flaring, and a density-metallicity bump possibly from radial migration.
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The Last Galactic Firework: Timing the last significant merger with stars, globular clusters and $\omega$Centauri
The Gaia-Sausage-Enceladus merger occurred 11.2 ± 0.1 Gyr ago, coinciding with the formation of a group of globular clusters and potentially leaving ω Centauri as its remnant, while placing disk formation at z ≳ 4.
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Sifting for a Stream: The Morphology of the $300S$ Stellar Stream
300S stellar stream exhibits three density peaks, smooth width variations, a possible 4.7 degree gap, and a kink modeled as resulting from Large Magellanic Cloud interaction across its full known footprint.
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Unsupervised Chemo-Dynamical Dissection of the Inner Galactic Halo: Discovery of Five Accreted Substructures with SDSS-V and Gaia
A blind 12D chemo-dynamical clustering analysis with UMAP and HDBSCAN on SDSS-V DR19 and Gaia DR3 data recovers seven known halo substructures and reports five new tightly bound candidates FO1-FO5.
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Gaia-Sausage-Enceladus: Lithium evolution from early red-giant-branch and main-sequence stars
A lithium chemical evolution model for the GSE galaxy matches survey data showing Spite-like and eRGB plateaus at low metallicity with a hint of reduced nova contributions.
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Inferring stellar metallicity and elemental abundances from kinematic and spectroscopic data using machine learning -- Implications for exoplanet host stars
ML regressors trained on APOGEE DR17 red giants predict C, O, Mg, Si abundances from kinematics and [Fe/H] more accurately than [Fe/H] baseline, with external validation on HARPS FGK dwarfs and reproduction of Galactic chemical evolution trends.
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Applying Liouville's Theorem to Gaia Data
Phase-space density is recovered from Gaia data for M4 and disrupted streams by correcting entropy injection and minimizing stream entropy, enabling original mass inference via Liouville's theorem.
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Life is But a Stream: The Distribution of Planetary Systems Along Stellar Streams and their Properties
Simulations show stars at the edges of stellar streams are more likely to retain unperturbed planetary systems than stars near the stream center.
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The First Infrared Portrait of A Solar-Like Host Star with Debris Disk: Pioneering High-Resolution H- and K-Band Spectroscopy of HD115617 with Comparative Optical Spectrum Analysis
The first NIR high-resolution spectroscopy of solar analog HD115617 shows a 250 K temperature discrepancy with optical data but confirms solar composition, main-sequence status, and no chemical signature of planetary formation.
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Build-up and survival of the disc: From numerical models of galaxy formation to the Milky Way
Simulations show that observed rotation in 13.5-Gyr-old alpha-rich stars constrains the Gaia-Sausage-Enceladus merger to mass ratios below 1:4, with interaction and starburst times both near 11 Gyr.
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Observational Signatures and Constraints on the Intermediate Neutron-Capture Process. The Case of the CEMP star TYC 6044-714-1 (RAVE J094921.8-161722)
High-precision abundances and Ba isotopic ratios in TYC 6044-714-1 favor an s+r nucleosynthesis scenario over i-process models, which require implausible conditions and mismatch isotopic data.
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Self-consistent dynamical modelling of the Milky Way bar with orbital frequency analysis
An updated orbital frequency method shows multiple Milky Way bar lengths and pattern speeds are consistent with star data within 5 percent.
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Mass Production of 2023 KMTNet Microlensing Planets. III: Three Planets from the Subprime Field
Three new planets detected via 2023 KMTNet microlensing with mass ratios log q ~ -1.9, -2.0, -2.6; overall 2023 sample of 25 planets matches prior mass-ratio distribution.
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Constraints on Einstein-aether gravity from the precision timing of PSR J1738+0333
Precision timing of PSR J1738+0333 from EPTA and NANOGrav data yields the tightest strong-field constraints on Einstein-aether parameters from any single binary pulsar.
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Multiwavelength Study of Blue Straggler Stars in Tombaugh 2: Evidence for Binary Mass Transfer and Constraints on Cluster Dynamical State
In Tombaugh 2, 32% of blue straggler stars show ultraviolet excess from hot companions consistent with recent binary mass transfer, supporting this channel over mergers in a low-density cluster.
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SED and Galactic kinematic diagnostics for dormant BH/NS binary candidates
SED fitting plus kinematic diagnostics identify 182 top dormant BH/NS binary candidates from Gaia DR3, with 19 likely black hole systems having companion masses >=3 solar masses.
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3I/ATLAS: In Search of the Witnesses to Its Voyage
No stellar flybys within the past 10 Myr and 500 pc in Gaia DR3 explain the present trajectory of 3I/ATLAS, which matches thin-disk kinematics despite its high peculiar velocity.
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Dynamical evolution of Milky Way globular clusters on the cosmological timescale II. Terzan 2, 4, and 5 mass loss and collision tracking
N-body simulations show that mutual interactions between Terzan 2, 4, and 5 raise mass-loss rates for the smaller clusters and drive prolate deformations absent in isolated runs.
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Classical Be Stars and Classical Be Star Binaries from LAMOST DR12
From LAMOST DR12, 504 classical Be stars are cataloged with 141 new, 14 RV-variable binaries, 60 RUWE-based candidates, 34 cluster members, and 37 runaways.
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The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
The paper reports on the Astropy v5.0 release, project updates, ecosystem connections, and challenges facing the community-oriented open-source astronomy software effort.
- Oort Cloud Ecology -- IV. Exchanging Asteroids