Stellar populations and origin of thick disks in AURIGA simulations

Abstract

The origin of thick disks and their evolutionary connection with thin disks are still a matter of debate. We provide new insights into this topic by connecting the stellar populations of thick disks at redshift $z=0$ with their past formation and growth, in 24 Milky Way-mass galaxies from the AURIGA zoom-in cosmological simulations. We projected each galaxy edge on, and decomposed it morphologically into two disk components, in order to define geometrically the thin and the thick disks as usually done in observations. We produced age, metallicity and [Mg/Fe] edge-on maps. We quantified the impact of satellite mergers by mapping the distribution of ex-situ stars. Thick disks are on average $\sim 3$~Gyr older, $\sim 0.25$~dex more metal poor and $\sim 0.06$~dex more [Mg/Fe]-enhanced than thin disks. Their average ages range from $\sim 6$ to $\sim 9$~Gyr, metallicities from $\sim -0.15$ to $\sim 0.1$~dex, and [Mg/Fe] from $\sim 0.12$ to $\sim 0.16$~dex. These properties are the result of an early initial in-situ formation, followed by a later growth driven by the combination of direct accretion of stars, some in-situ star formation fueled by mergers, and dynamical heating of stars. The balance between these processes varies from galaxy to galaxy. Mergers play a key role in the mass assembly of thick disks, contributing an average accreted mass fraction of $\sim 22$\% in the analyzed thick-disk dominated regions. In two galaxies, about half of the geometric thick-disk mass was directly accreted. While primordial thick disks form at high redshift in all galaxies, young metal-rich thin disks, with much lower [Mg/Fe] abundances, start to form later but at different times (higher or lower redshift) depending on the galaxy. We conclude that thick disks result from the interplay of external processes with the internal evolution of the galaxy.

arXiv comment57 pages, 43 figures, 3 tables; Published in Astronomy & Astrophysics

References in corpus (75)

• emcee: The MCMC Hammer
• Stellar population synthesis at the resolution of 2003
• Galactic Stellar and Substellar Initial Mass Function
• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• E pur si muove: Galiliean-invariant cosmological hydrodynamical simulations on a moving mesh
• Parametric Recovery of Line-of-Sight Velocity Distributions from Absorption-Line Spectra of Galaxies via Penalized Likelihood
• Adaptive spatial binning of integral-field spectroscopic data using Voronoi tessellations
• Chemical Cartography with APOGEE: Metallicity Distribution Functions and the Chemical Structure of the Milky Way Disk
• Simulations of Galaxy Formation in a Lambda CDM Universe II: The Fine Structure of Simulated Galactic Disks
• The history of star formation in a LCDM universe
• The Arepo public code release
• The Emergence of the Thick Disk in a CDM Universe
• NIHAO project I: Reproducing the inefficiency of galaxy formation across cosmic time with a large sample of cosmological hydrodynamical simulations
• Evidence from the H3 Survey that the Stellar Halo is Entirely Comprised of Substructure
• The thick disks of spiral galaxies as relics from gas-rich, turbulent, clumpy disks at high redshift
• Improving the convergence properties of the moving-mesh code AREPO
• The Biggest Splash
• The origin of accreted stellar halo populations in the Milky Way using APOGEE, $\text{Gaia}$, and the EAGLE simulations
• The birth of the Milky Way as uncovered by accurate stellar ages with Gaia
• The SAURON project - XII. Kinematic substructures in early-type galaxies: evidence for disks in fast rotators
• From dawn till disk: Milky Way's turbulent youth revealed by the APOGEE+Gaia data
• Optical colours and spectral indices of $z=0.1$ EAGLE galaxies with 3D dust radiative transfer code SKIRT
• On the Formation of Galactic Thick Disks
• The Auriga Stellar Haloes: Connecting stellar population properties with accretion and merging history
• Vertical disc heating in Milky Way-sized galaxies in a cosmological context
• On the origin of the chemical bimodality of disk stars: A tale of merger and migration
• VINTERGATAN I: The origins of chemically, kinematically and structurally distinct discs in a simulated Milky Way-mass galaxy
• The EAGLE simulations: atomic hydrogen associated with galaxies
• Origin of chemically distinct discs in the Auriga cosmological simulations
• The distribution of atomic hydrogen in EAGLE galaxies: morphologies, profiles, and HI holes
• Sausage & Mash: The dual origin of the Galactic thick disc and halo from the gas-rich Gaia-Enceladus-Sausage merger
• A diversity of progenitors and histories for isolated spiral galaxies
• Gas accretion and galactic fountain flows in the Auriga cosmological simulations: angular momentum and metal re-distribution
• The imprint of clump formation at high redshift. I. A disc alpha-abundance dichotomy
• Dissecting simulated disc galaxies II: the age-velocity relation
• The origin of diverse $\alpha$-element abundances in galaxy discs
• Warps and waves in the stellar discs of the Auriga cosmological simulations
• Orbital decomposition of CALIFA spiral galaxies
• The Fornax 3D project: unveiling the thick disk origin in FCC 170: signs of accretion?
• Kinematics of Simulated Galaxies I: Connecting Dynamical and Morphological Properties of Early-Type Galaxies at Different Redshifts
• A Systematic Look at the Effects of Radiative Feedback on Disc Galaxy Formation
• Neutron star mergers and rare core-collapse supernovae as sources of r-process enrichment in simulated galaxies
• The Kinematics of Thick Disks in Nine External Galaxies
• The Kinematics of Thick Disks in External Galaxies
• Exploring the mass assembly of the early-type disc galaxy NGC3115 with MUSE
• Lick Indices in the Thin and Thick Disks of Edge-On Disk Galaxies
• Properties of HI discs in the Auriga cosmological simulations
• Spurious heating of stellar motions in simulated galactic disks by dark matter halo particles
• The bursty origin of the Milky Way thick disc
• Dissecting simulated disc galaxies I: the structure of mono-age populations
• Lessons from the Auriga discs: The hunt for the Milky Way's ex-situ disc is not yet over
• Aurigaia: mock Gaia DR2 stellar catalogues from the Auriga cosmological simulations
• The reports of thick discs' deaths are greatly exaggerated: thick discs are NOT artefacts caused by diffuse scattered light
• Effects of simulated cosmological magnetic fields on the galaxy population
• Chasing the impact of the Gaia-Sausage-Enceladus merger on the formation of the Milky Way thick disc
• The formation of a thick disk through the heating of a thin disk: Agreement with orbital eccentricities of stars in the solar neighborhood
• The Fornax 3D project: Thick disks in a cluster environment
• Impacts of a Flaring Star-forming Disc and Stellar Radial Mixing on the Vertical Metallicity Gradient
• A comparison of black hole growth in galaxy mergers with Gasoline and Ramses
• Structural and photometric properties of barred galaxies from the Auriga cosmological simulations
• The Diversity of Thick Galactic Discs
• The vertical structure of gaseous galaxy discs in cold dark matter halos
• NGC 5746: formation history of a massive disc-dominated galaxy
• The kinematics of local thick discs do not support an accretion origin
• A monolithic collapse origin for the thin/thick disc structure of ESO 243-49
• Kinematic analysis of EAGLE simulations: Evolution of ${\lambda }_{Re}$ and its connection with mergers and gas accretion
• An [$\alpha$/Fe]-enhanced thick disk in a Milky Way Analogue
• EAGLE-Auriga: effects of different subgrid models on the baryon cycle around Milky Way-mass galaxies
• An excessively massive thick disc of the enormous edge-on lenticular galaxy NGC7572
• Modeling multi-phase gases in cosmological simulations using compressible multi-fluid hydrodynamics
• On the Flaring of Thick Disc of Galaxies: Insights from Simulations
• Using Artificial Neural Networks to Constrain the Halo Baryon Fraction during Reionization
• A Blueprint for the Milky Way's Stellar Populations. IV. A String of Pearls $-$ the Galactic Starburst Sequence
• The vertical structure of the spiral galaxy NGC 3501: first stages of the formation of a thin metal-rich disc
• Local variations of the Stellar Velocity Ellipsoid-I: the disc of galaxies in the Auriga simulations

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• The GECKOS Survey: Identifying kinematic sub-structures in edge-on galaxies
• Chronology of our Galaxy from Gaia colour-magnitude diagram fitting (ChronoGal) II. Unveiling the formation and evolution of the kinematically selected Thick and Thin Discs
• BANG-MaNGA: A census of kinematic discs and bulges across mass and star formation in the local Universe
• The AGORA High-resolution Galaxy Simulations Comparison Project. VIII: Disk Formation and Evolution of Simulated Milky Way Mass Galaxy Progenitors at $1<z<5$
• Relatively young thick disks in star-forming late-type galaxies
• Bulgeless Evolution And the Rise of Discs (BEARD) II. The role of mergers in shaping the Milky Way analogues in TNG50
• Stellar halos of bright central galaxies II: Scaling relations, colors and metallicity evolution with redshift