Thin, thick and dark discs in ΛCDM

By Justin I. Read, George Lake, O. Agertz, V. Debattista. 2008

258 citations recorded by the source corpus.

In acold dark matter (� CDM) cosmology, the Milky Way accretes satellites into the stellar disc. We use cosmological simulations to assess the frequency of near disc plane and higher inclination accretion events, and collisionless simulations of satellite mergers to quantify the final state of the accreted material and the effect on the thin disc. On average, a Milky Way-sized galaxy has three subhaloes with vmax > 80 km s −1 ; seven with vmax > 60 km s −1 and 15 with vmax > 40 km s −1 merge at redshift z 1. Assuming isotropic accretion, a third of these merge at an impact angle θ 20 ◦ are twice as likely as low-inclination ones. These lead to structures that closely resemble the recently discovered inner and outer stellar haloes. They also do more damage to the Milky Way stellar disc creating a more pronounced flare, and warp; both long-lived and consistent with current observations. The most massive mergers (vmax 80 km s −1 ) heat the thin disc enough to produce a thick disc. These heated thin-disc stars are essential for obtaining a thick disc as massive as that seen in the Milky Way; they likely comprise some ∼50-90 per cent of the thick disc stars. The Milky Way thin disc must reform from fresh gas after z = 1. Only one in four of our sample Milky Way haloes experiences mergers massive and late enough to fully destroy the thin disc. We conclude that thick, thin and dark discs occur naturally within aCDM cosmology.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/07359132cbcecf3b38f2003813861d19875994b5

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In Astronomy and Astrophysics

1. P. Hopkins
2. M. Cappellari
3. Volker Springel
4. L. Hernquist
5. T. Naab
6. Simon D. M. White
7. A. Dekel
8. R. Dav'e

In Instrumentation

1. M. Cappellari
2. P. Hopkins
3. L. Hernquist
4. Volker Springel
5. T. Naab
6. Simon D. M. White
7. A. Dekel
8. R. Dav'e

Citations in the corpus

• Galactic Searches for Dark Matter (2012, methodology): “As discussed in more detail in Section 5, a dark matter disk is predicted to exist from cosmological simulations (Read et al., 2008), however using methods similar to those described above there is not yet kinematical evidence for such a structure in the Milky Way (Bidin et al., 2010).”
• Dissecting simulated disc galaxies - I. The structure of mono-age populations (2014, result): “We also find a significant flaring in populations affected by mergers, as already discussed in a number of previous works (Quinn, Hernquist, & Fullagar 1993; Kazantzidis et al. 2008; Read et al. 2008; Villalobos & Helmi 2008; Bournaud, Elmegreen, & Martig 2009; Qu et al. 2011).”
• THICK DISKS OF EDGE-ON GALAXIES SEEN THROUGH THE SPITZER SURVEY OF STELLAR STRUCTURE IN GALAXIES (S4G): LAIR OF MISSING BARYONS? (2011, background): “…galaxy–galaxy or dark matter subhalo–galaxy interactions and mergers (Quinn et al. 1993; Robin et al. 1996; Walker et al. 1996; Velázquez & White 1999; Chen et al. 2001; Benson et al. 2004; Hayashi & Chiba 2006; Kazantzidis et al. 2008; Read et al. 2008; Villalobos & Helmi 2008; Qu et al. 2011).”
• A DIRECT DYNAMICAL MEASUREMENT OF THE MILKY WAY'S DISK SURFACE DENSITY PROFILE, DISK SCALE LENGTH, AND DARK MATTER PROFILE AT 4 kpc ≲ R ≲ 9 kpc (2013, background): “Our results leave little room for a dark disk component in the Milky Way (Read et al. 2008), because the presence of such a component would increase our estimates of the local surface density and of the mass scale length.”
• MORPHOLOGICAL QUENCHING OF STAR FORMATION: MAKING EARLY-TYPE GALAXIES RED (2009, methodology): “A similar approach has been independently proposed by Kazantzidis et al. (2008), Read et al. (2008) and Villalobos & Helmi (2008), but these authors account only for the main mergers and not for the diffuse accretion, and only performed collisionless simulations without any gas component, and…”
• KINEMATICAL AND CHEMICAL VERTICAL STRUCTURE OF THE GALACTIC THICK DISK. II. A LACK OF DARK MATTER IN THE SOLAR NEIGHBORHOOD, (2012, background): “In Figure 10 our results are compared to the expectations of the massive DM disk model of Kalberla (2003), the thick, low-density model of Purcell et al. (2009), and the thinner and denser ones from Read et al. (2008).”
• Impact of baryon physics on dark matter structures: a detailed simulation study of halo density profiles (2010, background): “This will lead to the accumulation of stars, and DM, in the same plane, forming both a thin stellar and a DM disc (Read et al. 2008).”
• Dark matter cores all the way down (2015, background): “…to Fornax being on a cosmologically bizarre near-circular orbit; while Carina has a median rp ∼ 45 kpc. Typical orbits in ΛCDM should have apo-to-peri ratios closer to 1:5 for the surviving satellites and 1:6 for the accreted ones (e.g. Kazantzidis et al. 2008; Read et al. 2008; Lux et al. 2010).”
• STARS, GAS, AND DARK MATTER IN THE SOLAR NEIGHBORHOOD (2015, background): “This dark disk is therefore distinct from the one conjectured to be produced by accreted satellite galaxies, which could create a disk of dark matter with a density in the range 0.25–1.5 times that of the halo dark matter but with a thickness 1 kpc (Read et al. 2008, 2009).”
• Revealing the dark matter halo with axion direct detection (2017, background): “They may even dominate the local DM density [101, 103]; however, as we will see, even if the dark disk is only a small fraction of the local DM density, it can still leave a significant signature in the direct detection data due to the small velocity dispersion and lag speed.”
• Galaxy Masses: A Review (2013, background): “The dark matter distribution can then be assumed to be approximately constant close to the Galactic plane (i.e., dark matter is distributed in a halo and not a disk (but see Read et al. (2008) for an alternative viewpoint.)”
• A new determination of the local dark matter density from the kinematics of K dwarfs (2012, background): “Even the ‘dark disc’ predicted by recent cosmological simulations (Read et al. 2008; Read et al. 2009) is sufficiently hot that its dark matter distribution is approximately constant up to ∼ 1 kpc.”
• The ATLAS3D project - VII. A new look at the morphology of nearby galaxies: the kinematic morphology-density relation (2011, background): “4 of Paper I; Dressler 1980), as is the presence of thick dis s in S0s (Burstein 1979), which are expected to form via dynamic l disturbances (Read et al. 2008).”