The origin of spin in galaxies: clues from simulations of atomic cooling halos

Abstract

In order to elucidate the origin of spin in both dark matter and baryons in galaxies, we have performed hydrodynamical simulations from cosmological initial conditions. We study atomic cooling haloes in the redshift range $100>z>9$ with masses of order $10^9{\mathrm{M}}_{\odot }$ at redshift $z=10$. We assume that the gas has primordial composition and that ${\mathrm{H}}_2$-cooling and prior star-formation in the haloes have been suppressed. We present a comprehensive analysis of the gas and dark matter properties of four halos with very low ($\lambda \approx 0.01$), low ($\lambda \approx 0.04$), high ($\lambda \approx 0.06$) and very high ($\lambda \approx 0.1$) spin parameter. Our main conclusion is that the spin orientation and magnitude is initially well described by tidal torque linear theory, but later on is determined by the merging and accretion history of each halo. We provide evidence that the topology of the merging region, i.e. the number of colliding filaments, gives an accurate prediction for the spin of dark matter and gas: halos at the center of knots will have low spin while those in the center of filaments will have high spin. The spin of a halo is given by $\lambda \approx 0.05\times {\left(\frac{7.6}{\mathrm{number}\mathrm{of}\mathrm{filaments}}\right)}^{5.1}$.

Submitted to MNRAS

References in corpus (5)

• Properties of Dark Matter Haloes in Clusters, Filaments, Sheets and Voids
• Fluctuations in the High-Redshift Lyman-Werner Background: Close Halo Pairs as the Origin of Supermassive Black Holes
• Initial Conditions for Large Cosmological Simulations
• Direct collapse black hole formation from synchronized pairs of atomic cooling halos
• Revisiting the effect of H2, HD and LiH molecules in the cooling of primordial gas

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