Beyond Inside-Out Growth: Formation and Evolution of Disk Outskirts

By Rok Roskar, V. Debattista, G. Stinson, Thomas R. Quinn, T. Kaufmann, James Wadsley. 2007

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We have performed a high mass and force resolution simulation of an idealized galaxy forming from dissipational collapse of gas embedded in a spherical dark matter halo. The simulation includes star formation and effects of stellar feedback. In our simulation a stellar disk forms with a surface density profile consisting of an inner exponential breaking to a steeper outer exponential. The break forms early on and persists throughout the evolution, moving outward as more gas is able to cool and add mass to the disk. The parameters of the break are in excellent agreement with observations. The break corresponds to a rapid drop in the star formation rate associated with a drop in the cooled gas surface density, but the outer exponential is populated by stars that were scattered outward on nearly circular orbits from the inner disk by spiral arms. The resulting profile and its associated break are therefore a consequence of the interplay between a radial star formation cutoff and redistribution of stellar mass by secular processes. A consequence of such evolution is a sharp change in the radial mean stellar age profile at the break radius.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/af2b4934a5e841e78b8bb5f397f1a59f7911a9e3

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Citations in the corpus

Radial migration does little for Galactic disc thickening (2012, background): “This “disc mixing” can give rise to a number of phenomena, such as flattening in radial metallicity gradients (e.g., Minchev et al., 2011a; Pilkington et al., 2012) and extended stellar density profiles (e.g., Roškar et al., 2008b; SánchezBlázquez et al., 2009; Minchev et al., 2012a).”
A FIRST CONSTRAINT ON THE THICK DISK SCALE LENGTH: DIFFERENTIAL RADIAL ABUNDANCES IN K GIANTS AT GALACTOCENTRIC RADII 4, 8, AND 12 kpc (2011, background): “And certainly, radial migration has surfaced as an important mechanism in the modelling of disk galaxies (e.g., Roškar et al. 2008a,b; Schönrich & Binney 2009a,b; Loebman et al. 2010).”
INSIDE OUT AND UPSIDE DOWN: TRACING THE ASSEMBLY OF A SIMULATED DISK GALAXY USING MONO-AGE STELLAR POPULATIONS (2013, background): “Radial migration of stars is also an important ingredient in understanding chemical evolutin (Wielen et al. 1996; Sellwood & Binney 2002; Roškar et al. 2008a; Schönrich & Binney 2009a), and it arises naturally in our simulation.”
Red Clump Stars from LAMOST II: the outer disc of the Milky Way (2017, background): “Simulations show that secular evolution of the discs can significantly alter their properties, from the age distribution to the stellar density profile of the outer disc (Roškar et al. 2008; Debattista et al. 2006).”
The Milky Way’s stellar disk (2013, background): “What has been the role of radial migration (Sellwood & Binney 2002; Roškar et al. 2008a,b; Schönrich & Binney 2008; Minchev et al. 2011), i.e., the substantive changes in the stars’ mean orbital radii that are expected to occur without boosting the orbits’ eccentricity?”
Mapping the Milky Way with LAMOST– III. Complicated spatial structure in the outer disc (2018, background): “In principle, the shape of the radial profile may be used to probe the secular evolution of the Galaxy (Debattista et al. 2006; Roškar et al. 2008).”
FORMATION AND EVOLUTION OF THE DISK SYSTEM OF THE MILKY WAY: [α/Fe] RATIOS AND KINEMATICS OF THE SEGUE G-DWARF SAMPLE (2011, methodology): “Correlations between Rotational Velocity and Metallicity According to the radial migration models (Sellwood & Binney 2002; Roškar et al. 2008a; Schönrich & Binney 2009a; Minchev & Famaey 2010), the (presumably) metal-poor stars of the thin disk (which includes young, low-[α/Fe] stars) that were…”
Evolution of galactic discs: multiple patterns, radial migration, and disc outskirts (2012, background): “Since old stars have longer timescales to populate the outer regions of galactic discs, this leads to a change in the radial mean stellar age profile at the break radius and a positive age gradient in outer disc (Roškar et al., 2008).”
The dynamics of stars around spiral arms (2011, background): “…mixing in spiral galaxies (e.g. Carlberg & Sellwood 1985; Amaral & Lepine 1997; Sellwood & Binney 2002; Minchev & Quillen 2006; Roškar et al. 2008a; Roškar et al. 2008b; Sánchez-Blázquez et al. 2009; Minchev et al. 2011) and in barred-spiral galaxies where a bar resonance is also included…”
The lifetimes of spiral patterns in disc galaxies (2010, background): “…spontaneously in simulations of isolated galaxies, from the first studies by Miller, Prendergast & Quirk (1970) and Hockney & Brownrigg (1974), right through to modern simulations that include more sophisticated physical processes (e.g. Ros̆kar et al. 2008a; Agertz, Teyssier & Moore 2010).”
THE LONG-TERM EVOLUTION OF THE GALACTIC DISK TRACED BY DISSOLVING STAR CLUSTERS (2010, methodology): “This process has now been seen in N-body simulations (gas+stars) of evolving disks that are kept sufficiently cool from halo gas accretion (Roškar et al 2008; Sánchez-Blázquez et al 2009), and the radial churning appears to be strong.”
The effects of radial migration on the vertical structure of Galactic discs (2012, background): “This radial migration has many important consequences for properties of stellar populations, such as giving rise to a flattened age-metallicity relation with substantial scatter (Sellwood & Binney 2002; Roškar et al.2008a; Schönrich & Binney 2009a).”
Misaligned angular momentum in hydrodynamic cosmological simulations: warps, outer discs and thick discs (2010, background): “We have previously addressed outer discs in the context of disc dynamics and stellar radial migration in (Roškar et al. 2008a,b, R08 collectively hereafter).”
Origin and structure of the Galactic disc(s) (2009, background): “…hereafter SB09) we showed that when one allows for radial mixing, which is an unavoidable consequence of spiral structure (Sellwood & Binney 2002; Roskar et al. 2008), a twocomponent disc arises naturally in the simplest model, in ⋆ E-mail: rasch@mpa-garching.mpg.de which the star-formation…”
Radial migration in disc galaxies — I. Transient spiral structure and dynamics (2011, background): “…has been important for the Milky Way, it most likely played a key role in determining the mix of stars in the solar neighborhood today (Sellwood & Binney 2002; Roškar et al. 2008b,a; Schönrich & Binney 2009a,b; Loebman et al. 2011; Minchev & Famaey 2010; Bird et al. 2012; Lee et al. 2011).”
A characteristic oxygen abundance gradient in galaxy disks unveiled with CALIFA (2013, background): “…and the drop in the oxygen abundance inward (together with the lack of evidence of any interaction and the low fraction of barred galaxies with these features) suggest that both features are the consequence of gas radial motions induced by resonances in the disk-speed pattern (Roškar et al. 2008b).”
Galaxy formation theory (2010, methodology): “For example, numerical simulations by Roskar et al. (2008b;see also Roskar et al. 2008a) show that a significant fraction of stars in galaxy disks undergo large migrations in radius (as shown in Fig.”
Chemical evolution with radial mixing (2008, methodology): “Our models are complementary to ab initio models of galaxy formation such as those presented by Samland & Gerhard (2003) and Roskar et al. (2008b) in that they allow the solar neighbourhood to be resolved in greater detail, and because they are enormously less costly numerically, they permit…”
Measuring Radial Orbit Migration in the Galactic Disk (2018, methodology): “In particular, radial orbit migrationhas been recognized as a potentially very important process in both analytic and simulation work (SB02; Roškar et al. 2008a; Minchev & Famaey 2010).”