Simulations of minor mergers - I. General properties of thick discs

Villalobos, Álvaro; Helmi, Amina

doi:10.1111/j.1365-2966.2008.13979.x

Cited by 301 publications

(364 citation statements)

References 104 publications

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“…Another possibility is that thick discs are created through the heating of preexisting thin discs by minor mergers (Di Matteo et al 2011;Villalobos & Helmi 2008). Evidence for merger encounters can be found in the phasespace structure of Milky Way disc stars (e.g., Gómez et al 2013Gómez et al , 2012bMinchev et al 2009).…”

Section: The Galactic Thick Discmentioning

confidence: 99%

“…The largest source is most likely satellite-disc interactions (e.g., Bournaud et al 2009;Villalobos & Helmi 2008), which have been found to increase an initially constant scale-height by up to a factor of ∼ 10 in 3-4 disc scalelengths. We showed in the left row of Fig.…”

Section: Migration Suppresses Disc Flaring When Infalling Satellites mentioning

confidence: 99%

“…In numerical simulations flaring is expected to result from a number of mechanisms related to galactic evolution in a cosmological context (e.g., Bournaud et al 2009;Kazantzidis et al 2008;Villalobos & Helmi 2008). Even in the absence of environmental effects, flaring is unavoidable due to secular evolution alone (radial migration caused by spirals and/or a central bar, Minchev et al 2012a).…”

Section: Migration Suppresses Disc Flaring When Infalling Satellites mentioning

confidence: 99%

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Constraining the Milky Way assembly history with Galactic Archaeology

Minchev

2016

Astron Nachr

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The aim of Galactic Archaeology is to recover the evolutionary history of the Milky Way from its present day kinematical and chemical state. Because stars move away from their birth sites, the current dynamical information alone is not sufficient for this task. The chemical composition of stellar atmospheres, on the other hand, is largely preserved over the stellar lifetime and, together with accurate ages, can be used to recover the birthplaces of stars currently found at the same Galactic radius. In addition to the availability of large stellar samples with accurate 6D kinematics and chemical abundance measurements, this requires detailed modeling with both dynamical and chemical evolution taken into account. An important first step is to understand the variety of dynamical processes that can take place in the Milky Way, including the perturbative effects of both internal (bar and spiral structure) and external (infalling satellites) agents. We discuss here (1) how to constrain the Galactic bar, spiral structure, and merging satellites by their effect on the local and global disc phase-space, (2) the effect of multiple patterns on the disc dynamics, and (3) the importance of radial migration and merger perturbations for the formation of the Galactic thick disc. Finally, we discuss the construction of Milky Way chemo-dynamical models and relate to observations.

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Section: The Galactic Thick Discmentioning

confidence: 99%

Section: Migration Suppresses Disc Flaring When Infalling Satellites mentioning

confidence: 99%

Section: Migration Suppresses Disc Flaring When Infalling Satellites mentioning

confidence: 99%

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Constraining the Milky Way assembly history with Galactic Archaeology

Minchev

2016

Astron Nachr

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“…Another possibility is that thick disks are created through the heating of preexisting thin disks with the help of mergers (Quinn et al 1993;Villalobos & Helmi 2008;Di Matteo et al 2011), whose rate decreases with decreasing redshift. Evidence for satellite-disk encounters can be found in structure in the phase-space of MW disk stars (e.g., Minchev et al 2009;Gómez et al 2013Gómez et al , 2012c, which can last for as long as ∼4 Gyr (Gómez et al 2012a).…”

Section: Thick-disk Formation Scenariosmentioning

confidence: 99%

Chemodynamical evolution of the Milky Way disk

Minchev

Chiappini

Martig

2013

A&A

442

574

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In the first paper of this series, we present a new approach for studying the chemo-dynamical evolution in disk galaxies, which consists of fusing disk chemical evolution models with compatible numerical simulations of galactic disks. This method avoids known star formation and chemical enrichment problems encountered in simulations. Here we focus on the Milky Way, by using a detailed thindisk chemical evolution model (matching local observables, which are weakly affected by radial migration) and a simulation in the cosmological context, with dynamical properties close to those of our Galaxy. We examine in detail the interplay between in situ chemical enrichment and radial migration and their impact on key observables in the solar neighborhood, e.g., the age-metallicityvelocity relation, the metallicity distribution, and gradients in the radial and vertical directions. We show that, due to radial migration from mergers at high redshift and the central bar at later times, a sizable fraction of old metal-poor high-[α/Fe] stars can reach the solar vicinity. This naturally accounts for a number of recent observations related to both the thin and thick disks, despite the fact that we use thin-disk chemistry only. Although significant radial mixing is present, the slope in the age-metallicity relation is only weakly affected, with a scatter compatible with recent observational work. While we find a smooth density distribution in the [O/Fe]-[Fe/H] plane, we can recover the observed discontinuity by selecting particles according to kinematic criteria used in high-resolution samples to define the thin and thick disks. We outline a new method for estimating the birth place of the Sun and predict that the most likely radius lies in the range 4.4 < r < 7.7 kpc (for a current location at r = 8 kpc). A new, unifying model for the Milky Way thick disk is offered, where both mergers and radial migration play a role at different stages of the disk evolution. We show that in the absence of early-on massive mergers the vertical velocity dispersion of the oldest stars is underestimated by a factor of ∼2 compared with observations. We can, therefore, argue that the Milky Way thick disk is unlikely to have been formed through a quiescent disk evolution. An observational test involving both chemical and kinematic information must be devised to ascertain this possibility.

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“…For example, they can induce changes that move late-type spiral galaxies towards earlier Hubble types and contribute to the thickening and heating of the stellar disk (Quinn et al 1993;Walker et al 1996;Velazquez & White 1999;Font et al 2001;Benson et al 2004;Kazantzidis et al 2008). The disks of galaxies are generally not fully destroyed by these events, and a remaining kinematically cold and thin component containing ∼15 to 25% of the initial stellar disk mass can indeed survive, embedded in a hotter and thicker disk (e.g., Villalobos & Helmi 2008), whereas the presence of gas in the disk galaxy can largely prevent the destruction of its thin stellar disk (Moster et al 2010).…”

Section: Introductionmentioning

confidence: 99%

The slowing down of galaxy disks in dissipationless minor mergers

Matteo

Lehnert

et al. 2010

A&A

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We have investigated the impact of dissipationless minor galaxy mergers on the angular momentum of the remnant. Our simulations cover a range of initial orbital characteristics, and the system consists of a massive galaxy with a bulge and disk merging with a much less massive (one-tenth or one-twentieth) gasless companion that has a variety of morphologies (disk-or elliptical-like) and central baryonic mass concentrations. During the process of merging, the orbital angular momentum is redistributed into the internal angular momentum of the final system; the internal angular momentum of the primary galaxy can increase or decrease depending on the relative orientation of the orbital spin vectors (direct or retrograde), while the initially nonrotating dark matter halo always gains angular momentum. The specific angular momentum of the stellar component always decreases independently of the orbital parameters or morphology of the satellite, the decrease in the rotation velocity of the primary galaxy is accompanied by a change in the anisotropy of the orbits, and the ratio of rotation speed to velocity dispersion of the merger remnant is lower than the initial value, not only because of an increase in the dispersion but also of the slowing-down of the disk rotation. We briefly discuss several astrophysical implications of these results, suggesting that minor mergers do not cause a "random walk" process of the angular momentum of the stellar disk component of galaxies, but rather a steady decrease. Minor mergers may play a role in producing the large scatter observed in the Tully-Fisher relation for S0 galaxies, as well as in the increase of the velocity dispersion and the decrease in v/σ at large radii as observed in S0 galaxies.

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Simulations of minor mergers - I. General properties of thick discs

Cited by 301 publications

References 104 publications

Constraining the Milky Way assembly history with Galactic Archaeology

Constraining the Milky Way assembly history with Galactic Archaeology

Chemodynamical evolution of the Milky Way disk

The slowing down of galaxy disks in dissipationless minor mergers

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