Thin disc, thick disc and halo in a simulated galaxy

By C. Brook, G. Stinson, Bradley K Gibson, Daisuke Kawata, E. House, M. Miranda, A. Macciò, K. Pilkington, Rok Roskar, James Wadsley and 1 more. 2012

156 citations recorded by the source corpus.

Within a cosmological hydrodynamical simulation, we form a disc galaxy with subcomponents which can be assigned to a thin stellar disc, thick disk, and a low mass stellar halo via a chemical decomposition. The thin and thick disc populations so selected are distinct in their ages, kinematics, and metallicities. Thin disc stars are young (<6.6 Gyr), possess low velocity dispersion (�U,V,W = 41,31,25 kms 1 ), high [Fe/H], and low [O/Fe]. Conversely, the thick disc stars are old (6.6<age<9.8 Gyrs), lag the thin disc by �21 km/s, possess higher velocity dispersion (�U,V,W = 49,44,35 kms 1 ), and have relatively low [Fe/H] and high [O/Fe]. The halo component comprises less than 4% of stars in the “solar annulus” of the simulation, has low metallicity, a velocity ellipsoid defined by (�U,V,W = 62,46,45 kms 1 ) and is formed primarily in-situ during an early merger epoch. Gas-rich mergers during this epoch play a major role in fuelling the formation of the old disc stars (the thick disc). We demonstrate that this is consistent with studies which show that cold accretion is the main source of a disc galaxy’s baryons. Our simulation initially forms a relatively short (scalelength �1.7kpc at z=1) and kinematically hot disc, primarily from gas accreted during the galaxy’s merger epoch. Far from being a competing formation scenario, we show that migration is crucial for reconciling the short, hot, discs which form at high redshift in �CDM, with the properties of the thick disc at z=0. The thick disc, as defined by its abundances maintains its relatively short scale-length at z = 0 (2.31kpc) compared with the total disc scale-length of 2.73kpc. The inside-out nature of disc growth is imprinted the evolution of abundances such that the metal poor �-young population has a larger scale-length (4.07kpc) than the more chemically evolved metal rich �-young population (2.74kpc).

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/13f0e85d8123e44e154b38aa42025bec2a70189e

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Citations in the corpus

Estimating stellar birth radii and the time evolution of Milky Way’s ISM metallicity gradient (2018, background): “1) and expected from a range of disk formation simulations (e.g., Roškar et al. 2008; Brook et al. 2012, Bird et al. 2013; Ma et al. 2017); • Resulting rbirth distribution of oldest mono-age bin peaks at ∼ 4 kpc - if this peak was located at a smaller radius, negative birth radii would result for…”
Constraining sub-grid physics with high-redshift spatially-resolved metallicity distributions (2013, methodology): “Predicted present-day, stellar mass-weighted, radial [O/Fe] gradients for the MaGICC (Brook et al. 2012b) and MUGS (Stinson et al. 2010) realisations of simulationg1536, compared with that predicted by an analytical model of the Milky Way (SB09: Schönrich & Binney (2009)).”
TRACING CHEMICAL EVOLUTION OVER THE EXTENT OF THE MILKY WAY'S DISK WITH APOGEE RED CLUMP STARS (2014, background): “…either a single or multiple sequence progression from low-metallicity, high-α to high-metallicity, low-α regions in the [O/Fe], [Fe/H] plane (e.g., Brook et al. 2012; Minchev et al. 2013; Stinson et al. 2013); others report relatively flat variation of [O/Fe] with [Fe/H] (e.g., Marinacci et al.…”
The masses and density profiles of halos in a LCDM galaxy formation simulation (2014, background): “…masses of haloes (Sawala et al. 2013, 2015; Cusworth et al. 2014; Velliscig et al. 2014; Vogelsberger et al. 2014) and in their inner structure (e.g. Gnedin et al. 2004; Pedrosa, Tissera & Scannapieco 2009; Duffy et al. 2010; Brook et al. 2012; Pontzen & Governato 2012; Di Cintio et al. 2014).”
The CALIFA survey across the Hubble sequence: Spatially resolved stellar population properties in galaxies (2015, background): “…galaxies can constrain the complex interplay between gas infall, outflows, stellar migration, radial gas flows, and star formation efficiency, in driving the inside-out growth of galactic disks (Brook et al. 2012; Gibson et al. 2013; Few et al. 2012; Pilkington et al. 2012a; Minchev et al. 2014).”
INSIDE OUT AND UPSIDE DOWN: TRACING THE ASSEMBLY OF A SIMULATED DISK GALAXY USING MONO-AGE STELLAR POPULATIONS (2013, methodology): “Brook et al. (2012) report a smooth transition in star formation from thick to thin disk stars, with the majority of their thin disk stars forming from smoothly accreted gas after the merger epoch.”
Constraining the Milky Way assembly history with Galactic Archaeology (2016, background): “The general formation and evolutionary behavior of this model is similar to many recent simulations in the cosmological context (e.g., Brook et al. 2012; Stinson et al. 2013).”
Confirming chemical clocks: asteroseismic age dissection of the Milky Way disc(s) (2017, background): “…chemical evolution before the younger low-α population built up (in agreement with cold dark matter predictions of decreasing merger rates, see e.g. Brook et al. 2004, 2012; Minchev et al. 2013; Stinson et al. 2013), or thick disc formation in large molecular clumps induced by instabilities in a…”
The age structure of stellar populations in the solar vicinity Clues of a two-phase formation history of the Milky Way disk (2013, background): “…have often claimed that radial migration is a fundamental mechanism in driving the evolution of a thick disk because, in these models, thick disk stars within the solar neighborhood are found with a variety of formation radii, frequently smaller than 4 kpc (Brook et al. 2012; Minchev et al. 2013).”
Reconstructing the star formation history of the Milky Way disc(s) from chemical abundances (2014, methodology): “We chose to follow these elements in addition to silicon because magnesium is also used in Haywood et al. (2013), and oxygen is both the dominant α element, and very common in numerical simulations, (e.g. Brook et al. 2012; Gibson et al. 2013).”
Chemodynamical evolution of the Milky Way disk II: Variations with Galactic radius and height above the disk plane (2014, result): “11) This is in agreement with recent results from simulations of spiral galaxies (e.g., Brook et al. 2012; Stinson et al. 2013; Bird et al. 2013) and observations in the MW (Bensby et al., 2011; Bovy et al., 2012b).”
THE RELATIONSHIP BETWEEN MONO-ABUNDANCE AND MONO-AGE STELLAR POPULATIONS IN THE MILKY WAY DISK (2016, result): “The general formation and evolutionary behavior of the disk formation is similar to many recent simulations in the cosmological context (e.g., Brook et al. 2012; Stinson et al. 2013; Bird et al. 2013; Marinacci et al. 2014).”
Numerical simulation of a possible origin of the positive radial metallicity gradient of the thick disk (2013, background): “…satellite accretion (Abadi et al. 2003; Yoachim & Dalcanton 2005), high redshift gas-rich mergers (Brook et al. 2004), radial migration (Roškar et al. 2008; Schönrich & Binney 2009) and a combination of high redshift gas-rich mergers and radial migration (Brook et al. 2012; Minchev et al. 2013).”
Chemodynamical evolution of the Milky Way disk - I. The solar vicinity (2012, background): “Additionally, the fraction of low-metallicity stars are often overestimated (Kobayashi and Nakasato, 2011; Calura et al., 2012), and reproducing the position of thin- and thick-disk stars in the [O/Fe]-[Fe/H] plane has proved challenging (Brook et al., 2012).”
The Galaxy in Context: Structural, Kinematic, and Integrated Properties (2016, background): “The dominant thin disk reflects a different form of accretion over the same long time frame (Brook et al. 2012).”