Combining Stellar Populations with Orbit-Superposition Dynamical Modelling - the Formation History of the Lenticular Galaxy NGC 3115

Abstract

We present a combination of the Schwarzschild orbit-superposition dynamical modelling technique with the spatially-resolved mean stellar age and metallicity maps to uncover the formation history of galaxies. We apply this new approach to a remarkable 5-pointing mosaic of VLT/MUSE observations obtained by Guérou et al. (2016) extending to a maximum galactocentric distance of $120^{\prime \prime }$ ($\sim 5.6\mathrm{kpc}$) along the major axis, corresponding to $\sim 2.5{\mathrm{R}}_e$. Our method first identifies `families' of orbits from the dynamical model that represent dynamically-distinct structures of the galaxy. Individual ages and metallicities of these components are then fit for using the stellar-population information. Our results highlight components of the galaxy that are distinct in the combined stellar dynamics/populations space, which implies distinct formation paths. We find evidence for a dynamically-cold, metal-rich disk, consistent with a gradual in-situ formation. This disk is embedded in a generally-old population of stars, with kinematics ranging from dispersion-dominated in the centre to an old, diffuse, metal-poor stellar halo at the extremities. We find also a direct correlation between the dominant dynamical support of these components, and their associated age, akin to the relation observed in the Milky Way. This approach not only provides a powerful model for inferring the formation history of external galaxies, but also paves the way to a complete population-dynamical model.

21 pages. 14 figures + appendices. Accepted for publication in MNRAS

References in corpus (39)

• Cold streams in early massive hot haloes as the main mode of galaxy formation
• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• Evolutionary Stellar Population Synthesis with MILES. Part I: The Base Models and a New Line Index System
• The SAURON project -- IX. A kinematic classification for early-type galaxies
• A systematic variation of the stellar initial mass function in early-type galaxies
• The KMOS^3D Survey: design, first results, and the evolution of galaxy kinematics from 0.7<z<2.7
• Compaction and Quenching of High-z Galaxies in Cosmological Simulations: Blue and Red Nuggets
• The Atlas3D Project - XXX. Star formation histories and stellar population scaling relations of early-type galaxies
• Triaxial orbit based galaxy models with an application to the (apparent) decoupled core galaxy NGC 4365
• A Supermassive Black Hole in an Ultracompact Dwarf Galaxy
• The mass distribution in early-type disk galaxies: declining rotation curves and correlations with optical properties
• The Structure and Dynamical Evolution of the Stellar Disk of a Simulated Milky Way-Mass Galaxy
• Spatially resolved spectroscopy of early-type galaxies over a range in mass
• Dissecting the Red Sequence--I. Star Formation Histories of Quiescent Galaxies: The Color-Magnitude vs. the Color-Sigma Relation
• NMAGIC: Fast Parallel Implementation of a Chi-Squared-Made-to-Measure Algorithm for Modelling Observational Data
• Two-dimensional multi-component photometric decomposition of CALIFA galaxies
• Age velocity dispersion relations and heating histories in disc galaxies
• Dissecting simulated disc galaxies II: the age-velocity relation
• Orbital decomposition of CALIFA spiral galaxies
• Timing the formation and assembly of early-type galaxies via spatially resolved stellar populations analysis
• IMF shape constraints from stellar populations and dynamics from CALIFA
• The age-velocity dispersion relation of the Galactic discs from LAMOST-Gaia data
• The SLUGGS survey: Exploring the metallicity gradients of nearby early-type galaxies to large radii
• Dominant dark matter and a counter rotating disc: MUSE view of the low luminosity S0 galaxy NGC 5102
• Rotation and Mass in the Milky Way and Spiral Galaxies
• A discrete chemo-dynamical model of the dwarf spheroidal galaxy Sculptor: mass profile, velocity anisotropy and internal rotation
• Systematic trends in total-mass profiles from dynamical models of early-type galaxies
• Recovery of the internal orbital structure of galaxies
• Spatially resolved variations of the IMF mass normalisation in early-type galaxies as probed by molecular gas kinematics
• Untangling galaxy components: full spectral bulge-disc decomposition
• Formation of S0 galaxies through mergers. Evolution in the Tully-Fisher relation since $z\sim 1$
• Galaxy structure from multiple tracers: III. Radial variations in M87's IMF
• Evaluating the ability of triaxial Schwarzschild modelling to estimate properties of galaxies from the Illustris simulation
• Abundance ratios and IMF slope in the dwarf elliptical galaxy NGC~1396 with MUSE
• A unified model for age-velocity dispersion relations in Local Group galaxies: Disentangling ISM turbulence and latent dynamical heating
• A discrete chemo-dynamical model of the giant elliptical galaxy NGC 5846: dark matter fraction, internal rotation and velocity anisotropy out to six effective radii
• Mass profile decomposition of the Frontier Fields cluster MACS J0416-02403. Insights on the Dark-Matter inner profile
• A photometric analysis of Abell 1689: two-dimensional multi-structure decomposition, morphological classification, and the Fundamental Plane
• Hierarchical Bayesian inference of the Initial Mass Function in Composite Stellar Populations