The Formation Times and Building Blocks of Milky Way-mass Galaxies in the FIRE Simulations

Abstract

Surveys of the Milky Way (MW) and M31 enable detailed studies of stellar populations across ages and metallicities, with the goal of reconstructing formation histories across cosmic time. These surveys motivate key questions for galactic archaeology in a cosmological context: when did the main progenitor of a MW/M31-mass galaxy form, and what were the galactic building blocks that formed it? We investigate the formation times and progenitor galaxies of MW/M31-mass galaxies using the FIRE-2 cosmological simulations, including 6 isolated MW/M31-mass galaxies and 6 galaxies in Local Group (LG)-like pairs at z = 0. We examine main progenitor "formation" based on two metrics: (1) transition from primarily ex-situ to in-situ stellar mass growth and (2) mass dominance compared to other progenitors. We find that the main progenitor of a MW/M31-mass galaxy emerged typically at z ~ 3-4 (11.6-12.2 Gyr ago), while stars in the bulge region (inner 2 kpc) at z = 0 formed primarily in a single main progenitor at z < 5 (< 12.6 Gyr ago). Compared with isolated hosts, the main progenitors of LG-like paired hosts emerged significantly earlier (Δz ~ 2, Δt ~ 1.6 Gyr), with ~ 4x higher stellar mass at all z > 4 (> 12.2 Gyr ago). This highlights the importance of environment in MW/M31-mass galaxy formation, especially at early times. Overall, about 100 galaxies with M_star > 10^5 M_sun formed a typical MW/M31-mass system. Thus, surviving satellites represent a highly incomplete census (by ~ 5x) of the progenitor population.

arXiv comment20 pages, 8 figures, accepted for publication in MNRAS

References in corpus (122)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• The NumPy array: a structure for efficient numerical computation
• Gaia Data Release 2. Summary of the contents and survey properties
• On the variation of the Initial Mass Function
• Starburst99: Synthesis Models for Galaxies with Active Star Formation
• The Formation of Galactic Disks
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• The Galaxy in Context: Structural, Kinematic and Integrated Properties
• The Rockstar Phase-Space Temporal Halo Finder and the Velocity Offsets of Cluster Cores
• UV Luminosity Functions at redshifts z~4 to z~10: 10000 Galaxies from HST Legacy Fields
• UniverseMachine: The Correlation between Galaxy Growth and Dark Matter Halo Assembly from z=0-10
• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• The New Galaxy: Signatures of its Formation
• GIZMO: A New Class of Accurate, Mesh-Free Hydrodynamic Simulation Methods
• FIRE-2 Simulations: Physics versus Numerics in Galaxy Formation
• A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: I. Morphology of the Sagittarius Core and Tidal Arms
• Tracing Galaxy Formation with Stellar Halos I: Methods
• Co-formation of the Galactic disc and the stellar halo
• The Radial Velocity Experiment (RAVE): first data release
• The GALAH Survey: Scientific Motivation
• Multi-scale initial conditions for cosmological simulations
• The Ghost of Sagittarius and Lumps in the Halo of the Milky Way
• A New Calculation of the Ionizing Background Spectrum and the Effects of HeII Reionization
• Reconciling dwarf galaxies with LCDM cosmology: Simulating a realistic population of satellites around a Milky Way-mass galaxy
• Gravitationally Consistent Halo Catalogs and Merger Trees for Precision Cosmology
• The APOSTLE simulations: solutions to the Local Group's cosmic puzzles
• Galactic stellar haloes in the CDM model
• The Auriga Project: the properties and formation mechanisms of disc galaxies across cosmic time
• A Merger-Driven Scenario for Cosmological Disk Galaxy Formation
• Forming Realistic Late-Type Spirals in a LCDM Universe: The Eris Simulation
• Age and Metallicity Distribution of the Galactic Bulge from Extensive Optical and Near-IR Stellar Photometry
• Formation of a spiral galaxy in a major merger
• The Cosmic Baryon Cycle and Galaxy Mass Assembly in the FIRE Simulations
• Tracing Galaxy Formation with Stellar Halos II: Relating Substructure in Phase- and Abundance-Space to Accretion Histories
• A Physical Model for the Origin of Quasar Lifetimes
• Asteroseismic fundamental properties of solar-type stars observed by the NASA Kepler Mission
• The formation and assembly history of the Milky Way revealed by its globular cluster population
• Not so lumpy after all: modeling the depletion of dark matter subhalos by Milky Way-like galaxies
• The First Cosmic Structures and their Effects
• ELVIS: Exploring the Local Volume in Simulations
• The Evolution of the Galaxy Stellar Mass Function at z= 4-8: A Steepening Low-mass-end Slope with Increasing Redshift
• Hierarchical galaxy formation and substructure in the Galaxy's stellar halo
• A Comparison of Methods for Determining the Molecular Content of Model Galaxies
• Breathing FIRE: How Stellar Feedback Drives Radial Migration, Rapid Size Fluctuations, and Population Gradients in Low-Mass Galaxies
• The birth of the Milky Way as uncovered by accurate stellar ages with Gaia
• The Pristine survey I: Mining the Galaxy for the most metal-poor stars
• Red giant masses and ages derived from carbon and nitrogen abundances
• The Assembly of Milky Way-like Galaxies Since z~2.5
• Merger Histories of Galaxy Halos and Implications for Disk Survival
• The stellar halo of the Galaxy
• The SAGA Survey: I. Satellite Galaxy Populations Around Eight Milky Way Analogs
• Galaxy Groups within 3500 km s${}^{-1}$
• The Local Group on FIRE: Dwarf galaxy populations across a suite of hydrodynamic simulations
• Chemodynamical history of the Galactic Bulge
• Chemical tagging with APOGEE: Discovery of a large population of N-rich stars in the inner Galaxy
• Gaia reveals a metal-rich in-situ component of the local stellar halo
• Gas kinematics, morphology, and angular momentum in the FIRE simulations
• Simulating galaxies in the reionization era with FIRE-2: galaxy scaling relations, stellar mass functions, and luminosity functions
• The Auriga Stellar Haloes: Connecting stellar population properties with accretion and merging history
• The MultiDark Database: Release of the Bolshoi and MultiDark Cosmological Simulations
• Feedback first: the surprisingly weak effects of magnetic fields, viscosity, conduction, and metal diffusion on galaxy formation
• Modelling chemical abundance distributions for dwarf galaxies in the Local Group: the impact of turbulent metal diffusion
• The Structure and Dynamical Evolution of the Stellar Disk of a Simulated Milky Way-Mass Galaxy
• Confirming chemical clocks: asteroseismic age dissection of the Milky Way disk(s)
• On the Last 10 Billion Years of Stellar Mass Growth in Star-Forming Galaxies
• Where are the most ancient stars in the Milky Way?
• ZFOURGE/CANDELS: On the Evolution of M* Galaxy Progenitors from z=3 to 0.5
• The ACS LCID Project: On the origin of dwarf galaxy types: a manifestation of the halo assembly bias?
• Dynamical Relics of the Ancient Galactic Halo
• How to Zoom: Bias, Contamination, and Lagrange Volumes in Multimass Cosmological Simulations
• Star formation histories of dwarf galaxies in the FIRE simulations: dependence on mass and Local Group environment
• The origin of the diverse morphologies and kinematics of Milky Way-mass galaxies in the FIRE-2 simulations
• A profile in FIRE: resolving the radial distributions of satellite galaxies in the Local Group with simulations
• Synthetic Gaia surveys from the FIRE cosmological simulations of Milky Way-mass galaxies
• Two distinct halo populations in the solar neighborhood. III. Evidence from stellar ages and orbital parameters
• Early formation and recent starburst activity in the nuclear disc of the Milky Way
• Tracing the formation of the Milky Way through ultra metal-poor stars
• The Caterpillar Project: A Large Suite of Milky Way Sized Halos
• The Eating Habits of Milky Way Mass Halos: Destroyed Dwarf Satellites and the Metallicity Distribution of Accreted Stars
• PLATO as it is: a legacy mission for Galactic archaeology
• Limits on Pop III star formation with the most iron-poor stars
• Self-Consistent Modeling of Reionization in Cosmological Hydrodynamical Simulations
• A Lonely Giant: The Sparse Satellite Population of M94 Challenges Galaxy Formation
• Decoding the stellar fossils of the dusty Milky Way progenitors
• The masses and metallicities of stellar haloes reflect galactic merger histories
• The Dragonfly Nearby Galaxies Survey. III. The Luminosity Function of the M101 Group
• The oldest and most metal poor stars in the APOSTLE Local Group simulations
• NIHAO-UHD: The properties of MW-like stellar disks in high resolution cosmological simulations
• The dwarf galaxy satellite system of Centaurus A
• Spectroscopic analysis of metal-poor stars from LAMOST: early results
• The Local Group as a time machine: studying the high-redshift Universe with nearby galaxies
• Characterizing solar-type stars from full-length Kepler data sets using the Asteroseismic Modeling Portal
• Star formation history of the Galactic bulge from deep HST imaging of low reddening windows
• Predicting the locations of possible long-lived low-mass first stars: Importance of satellite dwarf galaxies
• The Spatial Distribution of the Galactic First Stars II: SPH Approach
• Stellar Ages through the Corners of the Boxy Bulge
• Prospects for chemically tagging stars in the Galaxy
• Seeding the Second Star: enrichment from population III, dust evolution, and cloud collapse
• Reconciling observed and simulated stellar halo masses
• Tracing the first stars and galaxies of the Milky Way
• Under the Firelight: Stellar Tracers of the Local Dark Matter Velocity Distribution in the Milky Way
• The WFC3 Galactic Bulge Treasury Program: Relative Ages of Bulge Stars of High and Low Metallicity
• The Spatial Distribution of the Galactic First Stars I: High-Resolution N-body Approach
• Orbital masses of nearby luminous galaxies
• Local Group Ultra-Faint Dwarf Galaxies in the Reionization Era
• Near-Field Limits on the Role of Faint Galaxies in Cosmic Reionization
• The dark matter assembly of the Local Group in constrained cosmological simulations of a LambdaCDM universe
• The Effects of Patchy Reionization on Satellite Galaxies of the Milky Way
• Galaxy formation with radiative and chemical feedback
• On the Relative Ages of the $\alpha$-Rich and $\alpha$-Poor Stellar Populations in the Galactic Halo
• The history of the dark and luminous side of Milky Way-like progenitors
• Stars made in outflows may populate the stellar halo of the Milky Way
• A Simple Phenomenological Model for Grain Clustering in Turbulence
• Exploring Simulated Early Star Formation in the Context of the Ultrafaint Dwarf Galaxies
• Reionization of the Milky Way, M31, and their satellites I: reionization history and star formation
• Push it to the limit: Local Group constraints on high-redshift stellar mass functions for Mstar > 10^5 Msun
• On the Mass Assembly History of the Local Group
• The Mass Growth and Stellar Ages of Galaxies: Observations versus Simulations
• Ages of 70 dwarfs of three populations in the solar neighborhood: considering O and C abundances in stellar models
• Selecting ultra-faint dwarf candidate progenitors in cosmological N-body simulations at high redshifts
• Extending Semi-numeric Reionisation Models to the First Stars and Galaxies
• Cosmic Reionization On Computers: Reionization Histories of Present-day Galaxies

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• Reconstructing the Last Major Merger of the Milky Way with the H3 Survey
• FIRE-3: Updated Stellar Evolution Models, Yields, & Microphysics and Fitting Functions for Applications in Galaxy Simulations
• Public data release of the FIRE-2 cosmological zoom-in simulations of galaxy formation
• Planes of satellites around Milky Way/M31-mass galaxies in the FIRE simulations and comparisons with the Local Group
• Gas infall and radial transport in cosmological simulations of Milky Way-mass disks
• 3-D gas-phase elemental abundances across the formation histories of Milky Way-mass galaxies in the FIRE simulations: initial conditions for chemical tagging
• The central densities of Milky Way-mass galaxies in cold and self-interacting dark matter models
• Disk settling and dynamical heating: histories of Milky Way-mass stellar disks across cosmic time in the FIRE simulations
• The Galaxy Progenitors of Stellar Streams around Milky Way-mass Galaxies in the FIRE Cosmological Simulations
• Great Balls of FIRE I: The formation of star clusters across cosmic time in a Milky Way-mass galaxy
• Streams on FIRE: Populations of Detectable Stellar Streams in the Milky Way and FIRE
• The origin of metal-poor stars on prograde disk orbits in FIRE simulations of Milky Way-mass galaxies
• Great Balls of FIRE II: The evolution and destruction of star clusters across cosmic time in a Milky Way-mass galaxy
• Neutron star mergers as the astrophysical site of the r-process in the Milky Way and its satellite galaxies
• Formation of Galactic Disks I: Why Did the Milky Way's Disk Form Unusually Early?
• Are the Milky Way and Andromeda unusual? A comparison with Milky Way and Andromeda Analogs
• DM halo morphological types of MW-like galaxies in the TNG50 simulation: Simple, Twisted, or Stretched
• Exploring metallicity-dependent rates of Type Ia supernovae and their impact on galaxy formation
• Reading the CARDs: the Imprint of Accretion History in the Chemical Abundances of the Milky Way's Stellar Halo
• Orbital dynamics and histories of satellite galaxies around Milky Way-mass galaxies in the FIRE simulations
• Relating the Diverse Merger Histories and Satellite Populations of Nearby Galaxies
• The observable properties of galaxy accretion events in Milky Way-like galaxies in the FIRE-2 cosmological simulations
• The relationship between age, metallicity, and abundances for disk stars in a simulated Milky Way galaxy
• Milky Way-est: Cosmological Zoom-in Simulations with Large Magellanic Cloud and Gaia-Sausage-Enceladus Analogs
• A Blueprint for the Milky Way's Stellar Populations. III. Spatial Distributions and Population Fractions of Local Halo Stars
• A jolt to the system: ram pressure on low-mass galaxies in simulations of the Local Group
• The dark side of FIRE: predicting the population of dark matter subhaloes around Milky Way-mass galaxies
• Inferring the Morphology of Stellar Distribution in TNG50: Twisted and Twisted-Stretched shapes
• Testing Feedback from Star Clusters in Simulations of the Milky Way Formation
• Using Action Space Clustering to Constrain the Accretion History of Milky Way like Galaxies
• On the Edge: the relation between stellar and dark matter haloes of Milky Way-mass galaxies
• The role of stochastic and smooth processes in regulating galaxy quenching
• Auriga Streams I: disrupting satellites surrounding Milky Way-mass haloes at multiple resolutions
• Chemical Abundances of the Typhon Stellar Stream
• Are Milky-Way-like galaxies like the Milky Way? A view from SDSS-IV/MaNGA
• Cosmological Simulations of Stellar Halos with Gaia Sausage-Enceladus Analogues: Two Sausages, One Bun?
• Turbulent gas-rich discs at high redshift: origin of thick stellar discs through 3D 'baryon sloshing'
• The global structure of the Milky Way's stellar halo based on the orbits of local metal-poor stars
• Observing EAGLE galaxies with JWST: predictions for Milky Way progenitors and their building blocks
• Improving Performance of Zoom-In Cosmological Simulations using Initial Conditions with Customized Grids
• Different Sodium enhancements among multiple populations of Milky Way globular clusters
• Orbital phase-driven biases in Galactic mass constraints from stellar streams
• Survivors and Zombies: The Quenching and Disruption of Satellites around Milky Way Analogs
• The effect of environment on the mass assembly history of the Milky Way and M31
• Build-up and survival of the disc: From numerical models of galaxy formation to the Milky Way
• Rise of the forsaken relics: connecting present-day stellar streams and phase-mixed galaxies to the Epoch of Reionization
• Timing Mass of the Local Group
• New families in our Solar neighborhood: applying Gaussian Mixture models for objective classification of structures in the Milky Way and in simulations
• Metallicity Structure in Galactic Longitude-Velocity Diagrams of the Milky Way Disk and FIRE-2 Simulations
• 3D elemental abundances of stars at formation across the histories of Milky Way-mass galaxies in the FIRE simulations
• The DORCHA suite: nature, nurture, and the phase space distribution of the Milky Way's high redshift progenitors today
• The long-term stability of the Vast Polar Structure and its connection to a possible previous passage of the LMC
• The COMBS Survey -- III. The Chemodynamical Origins of Metal-Poor Bulge Stars