Identifying kinematic structures in simulated galaxies using unsupervised machine learning

Abstract

Galaxies host a wide array of internal stellar components, which need to be decomposed accurately in order to understand their formation and evolution. While significant progress has been made with recent integral-field spectroscopic surveys of nearby galaxies, much can be learned from analyzing the large sets of realistic galaxies now available through state-of-the-art hydrodynamical cosmological simulations. We present an unsupervised machine learning algorithm, named auto-GMM, based on Gaussian mixture models, to isolate intrinsic structures in simulated galaxies based on their kinematic phase space. For each galaxy, the number of Gaussian components allowed by the data is determined through a modified Bayesian information criterion. We test our method by applying it to prototype galaxies selected from the cosmological simulation IllustrisTNG. Our method can effectively decompose most galactic structures. The intrinsic structures of simulated galaxies can be inferred statistically by non-human supervised identification of galaxy structures. We successfully identify four kinds of intrinsic structures: cold disks, warm disks, bulges, and halos. Our method fails for barred galaxies because of the complex kinematics of particles moving on bar orbits.

arXiv commentAccepted for publication in ApJ, 14 pages, 12 figures

References in corpus (68)

• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• Detailed Structural Decomposition of Galaxy Images
• Introducing the Illustris Project: Simulating the coevolution of dark and visible matter in the Universe
• Simulating Galaxy Formation with the IllustrisTNG Model
• First results from the IllustrisTNG simulations: matter and galaxy clustering
• Secular Evolution and the Formation of Pseudobulges in Disk Galaxies
• First results from the IllustrisTNG simulations: the stellar mass content of groups and clusters of galaxies
• The Galaxy in Context: Structural, Kinematic and Integrated Properties
• The EAGLE simulations of galaxy formation: calibration of subgrid physics and model variations
• Properties of galaxies reproduced by a hydrodynamic simulation
• First results from the IllustrisTNG simulations: A tale of two elements -- chemical evolution of magnesium and europium
• Simulating galaxy formation with black hole driven thermal and kinetic feedback
• CALIFA, the Calar Alto Legacy Integral Field Area survey: I. Survey presentation
• The Atlas3D project -- I. A volume-limited sample of 260 nearby early-type galaxies: science goals and selection criteria
• First results from the IllustrisTNG simulations: radio haloes and magnetic fields
• Introducing the Illustris Project: the evolution of galaxy populations across cosmic time
• First Results from the TNG50 Simulation: The evolution of stellar and gaseous disks across cosmic time
• Structure and Formation of Elliptical and Spheroidal Galaxies
• The SAURON project -- IX. A kinematic classification for early-type galaxies
• The ATLAS3D project - III. A census of the stellar angular momentum within the effective radius of early-type galaxies: unveiling the distribution of Fast and Slow Rotators
• Simulations of Galaxy Formation in a Lambda CDM Universe II: The Fine Structure of Simulated Galactic Disks
• The Auriga Project: the properties and formation mechanisms of disc galaxies across cosmic time
• Galactic stellar haloes in the CDM model
• Forming Realistic Late-Type Spirals in a LCDM Universe: The Eris Simulation
• Structure and Kinematics of Early-Type Galaxies from Integral-Field Spectroscopy
• The Horizon-AGN simulation: morphological diversity of galaxies promoted by AGN feedback
• The optical morphologies of galaxies in the IllustrisTNG simulation: a comparison to Pan-STARRS observations
• The Atlas3D project - VII. A new look at the morphology of nearby galaxies: the kinematic morphology-density relation
• Our Milky Way as a Pure-Disk Galaxy -- A Challenge for Galaxy Formation
• The formation of disc galaxies in high resolution moving-mesh cosmological simulations
• Structural Parameters of Thin and Thick Disks in Edge-On Disk Galaxies
• Triaxial orbit based galaxy models with an application to the (apparent) decoupled core galaxy NGC 4365
• Characterizing Bars at z~0 in the optical and NIR: Implications for the Evolution of Barred Disks with Redshift
• The formation of disc galaxies in a LCDM universe
• Imfit: A Fast, Flexible New Program for Astronomical Image Fitting
• Evidence for Secular Evolution in Late-Type Spirals
• Towards a more realistic population of bright spiral galaxies in cosmological simulations
• Thin disc, Thick Disc and Halo in a Simulated Galaxy
• Double-Barred Galaxies: I. A Catalog of Barred Galaxies with Stellar Secondary Bars and Inner Disks
• A Structural and Dynamical Study of Late-Type, Edge-On Galaxies: II. Vertical Color Gradients and the Detection of Ubiquitous Thick Disks
• The abundance, distribution, and physical nature of highly ionized oxygen OVI, OVII, and OVIII in IllustrisTNG
• Difficulties with Recovering The Masses of Supermassive Black Holes from Stellar Kinematical Data
• The Auriga Stellar Haloes: Connecting stellar population properties with accretion and merging history
• Separation of Stellar Populations by an Evolving Bar: Implications for the Bulge of the Milky Way
• Feedback and the Structure of Simulated Galaxies at redshift z=2
• Halo Mass and Assembly History Exposed in the Faint Outskirts: the Stellar and Dark Matter Haloes of Illustris Galaxies
• The Structure and Dynamical Evolution of the Stellar Disk of a Simulated Milky Way-Mass Galaxy
• Stellar haloes of simulated Milky Way-like galaxies: Chemical and kinematic properties
• MaGICC Thick Disk I: Comparing a Simulated Disk Formed with Stellar Feedback to the Milky Way
• Barred galaxies in the EAGLE cosmological hydrodynamical simulation
• Tidally induced bars in Illustris galaxies
• Orbital decomposition of CALIFA spiral galaxies
• The Hubble Sequence at $z\sim 0$ in the IllustrisTNG simulation with deep learning
• On the Radio Detectability of Circumplanetary Discs
• A Systematic Look at the Effects of Radiative Feedback on Disc Galaxy Formation
• Pseudobulge Formation as a Dynamical Rather than a Secular Process
• NIHAO VI. The hidden discs of simulated galaxies
• The origin of pseudobulges in cosmological simulations of galaxy formation
• Stellar Halos in Illustris- Probing the Histories of Milky Way-Mass Galaxies
• The thick disk in the galaxy NGC 4244 from S4G imaging
• Formation of galaxies in ΛCDM cosmologies. I. The fine structure of disc galaxies
• Evidence for the concurrent growth of thick discs and central mass concentrations from S${}^4$G imaging
• Thick Disks in the Hubble Space Telescope Frontier Fields
• Introducing galactic structure finder: the multiple stellar kinematic structures of a simulated Milky Way mass galaxy
• The Carnegie-Irvine Galaxy Survey. VIII. Demographics of Bulges along the Hubble Sequence
• NIHAO XVI: The properties and evolution of kinematically selected discs, bulges and stellar haloes
• The innate origin of radial and vertical gradients in a simulated galaxy disc
• Cosmological simulations of Milky Way-sized galaxies

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• Mock Observations: Morphological Analysis of Galaxies in TNG100 Simulations
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• Testing the key role of the stellar mass-halo mass relation in galaxy merger rates and morphologies via DECODE, a novel Discrete statistical sEmi-empiriCal mODEl