A Universal Angular Momentum Profile for Galactic Halos

By James S. Bullock, A. Dekel, T. Kolatt, Andrey V. Kravtsov, Anatoly Klypin, C. Porciani, Joel R. Primack. 2000

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We study the angular momentum profiles of a statistical sample of halos drawn from a high-resolution N-body simulation of the ΛCDM cosmology. We find that the cumulative mass distribution of specific angular momentum j in a halo of mass Mv is well fitted by a universal function, M(< j) = Mvμj/(j0 + j). This profile is defined by one shape parameter (μ or j0) in addition to the global spin parameter λ. It follows a power law M(< j) ∝ j over most of the mass and flattens at large j, with the flattening more pronounced for small values of μ (or large j0 at a fixed λ). Compared to a uniform sphere in solid-body rotation, most halos have a higher fraction of their mass in the low- and high-j tails of the distribution. High-λ halos tend to have high μ values, corresponding to a narrower, more uniform j distribution. The spatial distribution of angular momentum in halos tends to be cylindrical and is well-aligned within each halo for ~80% of the halos. The more misaligned halos tend to have low μ values. When averaged over spherical shells encompassing mass M, the halo j profiles are fitted by j(M) ∝ Ms with s = 1.3 ± 0.3. We investigate two ideas for the origin of this profile. The first is based on a revised version of linear tidal-torque theory combined with extended Press-Schechter mass accretion, and the second focuses on j transport in minor mergers. Finally, we briefly explore implications of the M(< j) profile on the formation of galactic disks assuming that j is conserved during an adiabatic baryonic infall. The implied gas density profile deviates from an exponential disk, with a higher density at small radii and a tail extending to large radii. The steep central density profiles may imply disk scale lengths that are smaller than observed. This is reminiscent of the "angular momentum problem" seen in hydrodynamic simulations, even though we have assumed perfect j conservation. A possible solution is to associate the central excesses with bulge components and the outer regions with extended gaseous disks.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

Cosmological smoothed particle hydrodynamics simulations: a hybrid multiphase model for star formation (2002, background): “The relative distribution of angular momentum within the halo was chosen under the assumption that the specific angular momenta j(r) of spherical shells are all aligned, and that their magnitude is given by the fitting formula j(r) = jmax ( M(r) Mvir )s (43) of Bullock et al. (2001).”
The universal mass accretion history of cold dark matter haloes (2001, background): “Together with the universal profiles for the density distribution (Navarro, Frenk & White 1997) and angular momentum (Bullock et al. 2001) of CDM haloes, such a universal mass accretion history provides a complete description of the structure and evolution of dark matter haloes, which can be used…”
On the onset of galactic winds in quiescent star forming galaxies (2007, background): “…& Hernquist 2003) or “angular momentum” (Navarro & Benz 1991; Sommer-Larsen et al. 1999; Steinmetz & Navarro 1999; Send offprint requests to: Y. Dubois Bullock et al. 2001; Maller & Dekel 2002; Abadi et al. 2003; Sommer-Larsen et al. 2003; Read & Gilmore 2005) problem, may all have the same…”
The morgana model for the rise of galaxies and active nuclei (2006, background): “A connected sophistication lies in taking into account the internal distribution of angular momentum, which behaves like JD(r) ∝ M(r)α (Warren et al. 1992; Bullock et al. 2001), with the exponent α ranging from 1 to 1.3.”
Gas physics, disk fragmentation, and bulge formation in young galaxies (2003, background): “Additionally, the angular momentum distributions of the forming dark halos have been calculated recently (Bullock et al., 2001; Chen & Jing, 2002).”
Tracing the dark matter sheet in phase space (2011, neutral): “(12) in Bullock et al. 2001).”
Assembly bias in the clustering of dark matter haloes (2006, background): “(5) Halo spin Halo spin can be conveniently defined through λ = | ~J |/( √ 2MV r200) where angular momentum ~J c© 0000 RAS, MNRAS 000, 000–000 and mass M are the values within a sphere of radius r200 and the circular velocity V is also evaluated at this radius (Bullock et al. 2001).”
The formation and survival of discs in a ΛcDM universe (2008, neutral): “(5) of Bullock et al. (2001) at r200.”
The evolution of dark matter halo properties in clusters, filaments, sheets and voids (2007, methodology): “We estimate the spin parameter (Peebles 1969) of a halo using the simplified form (Bullock et al. 2001) λ′ ≡ |Jvir|√ 2MvirVvirRvir .”
A Revised Model for the Formation of Disk Galaxies: Low Spin and Dark Halo Expansion (2006, methodology): “To be able to account for this, we consider σ ln c a free parameter and compute c(M vir ) using the relation by Bullock et al. (2001a) but multiplied by a free parameter η c .”
The local dark matter density (2014, background): “Although there is significant scatter in rs at a given M200, there is a correlation between the two (Navarro et al., 1996b; Bullock et al., 2001; Macciò et al., 2007).”
THE COUPLING BETWEEN THE CORE/CUSP AND MISSING SATELLITE PROBLEMS (2012, methodology): “For example, the halo virial radiusrvir = rvir(Mvir ,z) is calculated from Bullock et al. (2001), whereas the concentration 7 Adopting Einasto profiles instead of NFW models has a negligible impact on our estimates.”
The Secular Evolution of Disk Structural Parameters (2005, background): “…baryons need not be like that of the dark halo (e.g. van den Bosch et al. 2002) and angular momentum distributions favoring disks more centrally concentrated than exponential (Firmani & Avila-Reese 2000; van den Bosch 2001; Bullock et al. 2001), secular evolution will also change disk structure.”
Cosmic ray feedback in hydrodynamical simulations of galaxy formation (2006, result): “We also impart angular momentum onto the halo with a distribution inside the halo consistent with results obtained from full cosmological simulations (Bullock et al., 2001).”
Multi-scale initial conditions for cosmological simulations (2011, methodology): “…radius Rvir, maximum circular velocity Vmax, the radius Rmax at which the circular velocity profile is maximal, the dimensionless spin parameter λ (Bullock et al. 2001), the three-dimensional velocity dispersion σ v as well as the minor-to-major axial ratio c/a, determined using the eigenvalues…”
Concentration, spin and shape of dark matter haloes: Scatter and the dependence on mass and environment (2006, methodology): “For this mass range we find c ∝ M−0.11vir , which is in agreement with the model of B01, but in disagreement with the model of ENS which predicts a significantly shallower slope.”
The Angular Momentum of Gas in Protogalaxies. I. Implications for the Formation of Disk Galaxies (2002, methodology): “…studies have investigated the resulting angular momenta of dark matter halos using either tidal torque theory (e.g., Peebles 1969; Doroshkevich 1970; White 1984; Catelan & Theuns 1996) or N-body simulations (e.g., Barnes & Efstathiou 1987; Warren et al. 1992; Bullock et al. 2001, hereafter B01).”
On the Maximum Luminosity of Galaxies and Their Central Black Holes: Feedback from Momentum-driven Winds (2004, background): “05 = λ/0.05 is the spin parameter of the dark matter halo (Bullock et al. 2001).”