Evolution of galactic discs: multiple patterns, radial migration, and disc outskirts

By I. Minchev, B. Famaey, A. Quillen, Paola Di Matteo, F. Combes, M. Vlajić, P. Erwin, Joss Bland-Hawthorn. 2012

155 citations recorded by the source corpus.

We investigate the evolution of galactic disks in N-body Tree-SPH simulations. We find that disks, initially truncated a t three scalelengths, can triple their radial extent, solely driven by se cular evolution. At the same time, the initial radial metall icity gradients are flattened and even reversed in the outer disks. Both Type I (si ngle exponential) and Type II (down-bending) observed disk surfacebrightness profiles can be explained by our findings. We show t hat profiles with breaks beyond the bar’s outer Lindblad reso nance, at present only explained as the effect of star-formation threshold, can occur even if no star fo rmation is considered. We explain these results with the strong angular momentum outward transfer, resulting from torques and radial migration associated with multiple patterns, such as central bars and spiral waves of different multiplicity. We find that even for stars ending up on co ld orbits, the changes in angular momentum exhibit complex structure as a function of radius, unlike the expected effect of transient spirals alone. We show that the bars in all of our simulations are the most effective drivers of radial migration through their corotatio n resonance, throughout the 3 Gyr of evolution studied. Focussing on one of our models, we find evidence for non-linear coupling among m = 1, 2, 3 and 4 density waves, where m is the pattern multiplicity. In this way the waves involved c onspire to carry the energy and angular momentum extracted by the first mode from the inner parts of the disk muc h farther out than a single mode could. We suggest that the naturally occurring larger resonance widths at galactic radii beyond four scale-lengths may have profound consequences on the formation and location of breaks in disk density profiles, provided spiral s are present at such large distances. We also consider the effect of gas inflow and show that when in-plane smooth gas accretion of∼ 5 M⊙/yr is included, the outer disks become more unstable, leading to a strong increase in the stellar velocity dispersion. This, i n turn, causes the formation of a Type III (up-bending) profil e in the old stellar population. We propose that observations of Type III surface brightness profiles, combined with an up-turn in the stella r velocity dispersions beyond the disk break, could be a signature of ongoing gas-accretion. The results of this study suggest that disk outskirts comprised of stars migrated from the inner disk would have relatively large radial velocity dispersions (> 30 km/s at 6 scale-lengths for Milky Way-size systems), and significant thickness when seen edge-on.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/9bd5585c6772032a337a695cc58cd318b2b921ac

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Citations in the corpus

Dissecting simulated disc galaxies - I. The structure of mono-age populations (2014, methodology): “Some authors have also argued that radial migration could create a thick disc (Schönrich & Binney 2009a,b; Loebman et al. 2011), although Minchev et al. (2012b) recently showed that radial migration alone is not efficient at heating discs.”
Radial migration in disc galaxies — I. Transient spiral structure and dynamics (2011, background): “Minchev & Famaey (2010); Minchev et al. (2011, 2012) argued that apart from corotation scattering as presented by SB02, combined effects of multiple nearby resonances from several different patterns may alsobe important in driving the redistribution of stars.”
Stellar population gradients in galaxy discs from the CALIFA survey - The influence of bars (2014, background): “…of attention in the literature over the past few years (Sellwood & Binney 2002; Roškar et al. 2008a,b; Berentzen et al. 2007; Minchev & Famaey 2010; Minchev et al. 2011, 2012a,b, 2014a,b; Grand et al. 2012a,b; Comparetta & Quillen 2012; Di Matteo et al. 2013; Brunetti et al. 2011; Shevchenko 2011;…”
The age structure of stellar populations in the solar vicinity Clues of a two-phase formation history of the Milky Way disk (2013, background): “…been discussed in the literature A109, page 14 of 18 (Sellwood & Binney 2002; Schönrich & Binney 2009a; Roškar et al. 2008; Minchev & Famaey 2010; Minchev et al. 2011, 2012a,b; Di Matteo et al. 2013) is the result of a secular process related to the presence of stellar asymmetries likes bars and…”
Estimating stellar birth radii and the time evolution of Milky Way’s ISM metallicity gradient (2018, background): “This origin coincides with the end of the Galactic bar, which is expected to produce most of the radial migration in the inner disk after its formation (e.g., Minchev et al. 2012a; Di Matteo et al. 2013).”
Constraining the Milky Way assembly history with Galactic Archaeology (2016, methodology): “The full description and simulation setup can be found in Minchev et al. (2012b).”
Radial migration does little for Galactic disc thickening (2012, methodology): “As we have shown in Minchev et al. (2012a), all of these models exhibit multiple patterns, giving rise to strong radial migration.”
The effects of radial migration on the vertical structure of Galactic discs (2012, methodology): “This is similar tothe model described by Minchev et al. (2012a), who use it to show tat the vertical velocity dispersion is expected to decrease asstar migrate outward if the vertical action is conserved.”
Chemodynamical evolution of the Milky Way disk - I. The solar vicinity (2012, background): “(2011b) and Minchev et al. (2012b), who demonstrated that migrators are generally not expected to heat the disk becaus of the approximate conservation of the average radial and vertical actions in the absence of external perturbers.”
Chemodynamical evolution of the Milky Way disk II: Variations with Galactic radius and height above the disk plane (2014, methodology): “This is in drastic contrast to the expected effect of outward migrators in a quiescent disk evolution, where stars arriving from the inner disk are slightly warmer than the non-migrating population (Minchev et al., 2012a).”
Constraints on Radial Migration in Spiral Galaxies - II. Angular momentum distribution and preferential migration (2018, unknown): “…et al. 2016 and for theoretical investigations see e.g. Sellwood & Binney 2002; Roškar et al. 2008; Schönrich & Binney 2009; Loebman et al. 2011; Minchev et al. 2012; Roškar, Debattista & Loebman 2013; Vera-Ciro, D’Onghia & Navarro 2016; Martinez-Medina et al. 2017; Peschken, Athanassoula &…”