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

By 'Alvaro Villalobos, A. Helmi. 2008

244 citations recorded by the source corpus.

We present simulations of the formation of thick discs via the accretion of two-component satellites onto a pre-existing thin disc. Our goal is to establish the detailed characteristics of the thick discs obtained in this way, as well as their dependence on the initial orbital and internal properties of the accreted objects. We find that mergers with 10-20 per cent mass of the host lead to the formation of thick discs whose characteristics are similar, both in morphology as in kinematics, to those observed. Despite the relatively large mass ratios, the host discs are not fully destroyed by the infalling satellites: a remaining kinematically cold and thin component containing similar to 15-25 per cent of the mass can be identified, which is embedded in a hotter and thicker disc. This may for example, explain the existence of a very old thin disc stars in the Milky Way. The final scaleheights of the discs depend both on the initial inclination and properties of the merger, but the fraction of satellite stellar particles at similar to 4 scaleheights directly measures the mass ratio between the satellite and host galaxy. Our thick discs typically show boxy isophotes at very low surface brightness levels (>6 mag below their peak value). Kinematically, the velocity ellipsoids of the simulated thick discs are similar to that of the Galactic thick disc at the solar radius. The trend of sigma(Z)/sigma(R) with radius is found to be a very good discriminant of the initial inclination of the accreted satellite. In the Milky Way, the possible existence of a vertical gradient in the rotational velocity of the thick disc as well as the observed value of sigma(Z)/sigma(R) at the solar vicinity appear to favour the formation of the thick disc by a merger with either low or intermediate orbital inclination.

Subfields: Astronomy and Astrophysics

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Citations in the corpus

Yule-Simpson’s paradox in Galactic Archaeology (2019, background): “…(e.g., Minchev et al. 2012, 2014a; Vera-Ciro et al. 2014; Grand et al. 2016, see also discussion in §1), except in redistributing stars heated by external mechanisms (Quinn et al. 1993; Villalobos & Helmi 2008) or turbulent gas clouds at high redshift (Bournaud et al. 2009; Forbes et al. 2012).”
The GALAH survey: scientific motivation (2015, background): “The origin of the thick disc is a matter of ongoing debate (e.g. Abadi et al. 2003; Brook et al. 2005; Villalobos & Helmi 2008; Loebman et al. 2011; Bovy et al. 2012; Minchev et al. 2012), with suggestions that it was accreted, heated from the thin disc by interactions with satellite galaxies,…”
Vertical density waves in the Milky Way disc induced by the Sagittarius dwarf galaxy (2012, background): “…radial migration, significantly flare or warp the disc, and influence the growth of a central bar (Tutukov & Fedorova 2006; Kazantzidis et al. 2008; Villalobos & Helmi 2008; Younger et al. 2008; Minchev et al. 2009; Quillen et al. 2009; Purcell et al. 2011; Bird et al. 2012; Gómez et al. 2012b).”
LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) — The survey's science plan (2012, background): “…(Statler 1988; Abadi et al. 2003); 2) heating of the pre-existing thin disk by the merging satellites (e.g. Quinn, Hernquist & Fullagar 1993; Villalobos & Helmi 2008); 3) in-situ triggered star formation during and after a gas-rich merger (e.g. Jones & Wyse 1983; Brook et al. 2004); and 4)…”
Thin, thick and dark discs in ΛCDM (2008, background): “Villalobos & Helmi (2008), also find that accreted stars can make up only a small fraction of the thick disc in the disc plane.”
THE GENESIS OF THE MILKY WAY'S THICK DISK VIA STELLAR MIGRATION (2010, methodology): “In contrast, Kazantzidis et al. (2008), Villalobos & Helmi (2008), and Villalobos et al. (2010) investigated substructure disruption by using a cosmologically derived satellite accretion history to perturb a Milky Way-like disk; subhalo-disk encounters increased the scale height of this disk at all…”
The structure and dynamical evolution of the stellar disc of a simulated Milky Way-mass galaxy (2016, background): “…(1) kinematic heating from a pre-existing thin disk during minor mergers (e.g. Quinn et al. 1993; Kazantzidis et al. 2008; Hopkins et al. 2008; Villalobos & Helmi 2008; Purcell et al. 2009; Qu et al. 2011), (2) star formation at high redshift from chaotic gas accretion during hierarchical…”
THICK DISKS OF EDGE-ON GALAXIES SEEN THROUGH THE SPITZER SURVEY OF STELLAR STRUCTURE IN GALAXIES (S4G): LAIR OF MISSING BARYONS? (2011, background): “The exception is the work by Villalobos & Helmi (2008), where the flare would only affect the thick disk at very large galactocentric radii, which would need deeper photometry than ours to be detected.”
The Milky Way’s stellar disk (2013, background): “…can be directly accreted (Abadi et al. 2003), or the disk can be heated through minor mergers (Toth & Ostriker 1992; Quinn et al. 1993; Kazantzidis et al. 2008; Villalobos & Helmi 2008; Moster et al. 2010) or experience a burst of star formation following a gasrich merger (Brook et al. 2004).”
THE RELATIONSHIP BETWEEN MONO-ABUNDANCE AND MONO-AGE STELLAR POPULATIONS IN THE MILKY WAY DISK (2016, background): “Mechanisms of thick disk formation include vertical heating from infalling satellites (e.g., Villalobos and Helmi 2008; Quinn et al. 1993), turbulent gas-rich disk phase at high redshift (e.g., Bournaud et al. 2009; Forbes et al. 2012), massive gas-rich satellites (Brook et al. 2004, 2005), and…”
Chemodynamics of the Milky Way - I. The first year of APOGEE data (2013, background): “Heating can be caused by, e.g., scattering off of giant molecular clouds (Spitzer & Schwarzschild 1951; Mihalas & Binney 1981), by interaction with the bar and spiral arms (Minchev et al. 2010; Minchev & Quillen 2006), or by merging satellites (Quinn et al. 1993; Villalobos & Helmi 2008).”
The age–metallicity structure of the Milky Way disc using APOGEE (2017, background): “Examples of such models include the heating of the old disk by high redshift mergers (e.g. Brook et al. 2004; Villalobos & Helmi 2008; Kazantzidis et al. 2009; Minchev et al. 2013) and the formation of a dual disk by gradual accretion of stars into disk orbits (e.g. Abadi et al. 2003).”
INSIDE OUT AND UPSIDE DOWN: TRACING THE ASSEMBLY OF A SIMULATED DISK GALAXY USING MONO-AGE STELLAR POPULATIONS (2013, background): “…stars stripped from satellites (Abadi et al. 2003), from a satellite dynamically heating a pre-existing stellar disk (e.g., Kazantzidis et al. 2008; Villalobos & Helmi 2008; Kazantzidis et al. 2009), from a gas rich merger at early times (Brook et al. 2004), from a clumpy and turbulent ISM at high…”
The influence of Sagittarius and the Large Magellanic Cloud on the stellar disc of the Milky Way Galaxy (2017, background): “…(Purcell et al. 2011) and dynamically cold ring-like features (Younger et al. 2008), thicken pre-existing thin discs (Velazquez & White 1999; Villalobos & Helmi 2008; Purcell, Bullock & Kazantzidis 2010), cause ringing in the u − v and E − Lz planes (Minchev et al. 2009; Gómez et al.…”
Galaxy formation theory (2010, background): “The stars from these smaller galaxies are often found in numerical simulations to form a thickened disk structure, in the same plane as the pre-existing disk of the galaxy (Abadi et al. 2003; Villalobos and Helmi 2008).”
Radial migration does little for Galactic disc thickening (2012, background): “Preexisting thin discs can be heated fast through the effect of multiple minor mergers (Quinn et al., 1993; Villalobos and Helmi, 2008; Di Matteo et al., 2011), the rate of which decreases with decreasing redshift.”
STRUCTURE AND KINEMATICS OF THE STELLAR HALOS AND THICK DISKS OF THE MILKY WAY BASED ON CALIBRATION STARS FROM SLOAN DIGITAL SKY SURVEY DR7 (2009, background): “Villalobos & Helmi (2008) have investigated in detail the heating process by a minor merger.”
A-type stars in the Canada–France Imaging Survey – II. Tracing the height of the disc at large distances with Blue Stragglers (2018, background): “…migration is expected to be less pronounced than in the case of a flare caused by disc–satellite impacts (Ibata & Razoumov 1998; Velazquez & White 1999; Kazantzidis et al. 2008; Villalobos & Helmi 2008; Bournaud, Elmegreen & Martig 2009; Purcell, Bullock & Kazantzidis 2010; Gómez et al. 2013).”