The abundance of (not just) dark matter haloes

Abstract

We study the effect of baryons on the abundance of structures and substructures in a cold dark matter (CDM) cosmology, using a pair of high-resolution cosmological simulations from the Galaxies-Intergalactic Medium Interaction Calculation project. Both simulations use identical initial conditions, but while one contains only dark matter, the other also includes baryons. We find that gas pressure, reionization, supernova feedback, stripping and truncated accretion systematically reduce the total mass and the abundance of structures below ∼10 12 M compared to the pure dark matter simulation. Taking this into account and adopting an appropriate detection threshold lower the abundance of observed galaxies with maximum circular velocities v max < 100 km s −1 , significantly reducing the reported discrepancy between CDM and the measured H I velocity function of the Arecibo Legacy Fast ALFA survey. We also show that the stellar-to-total mass ratios of galaxies with stellar masses of ∼10 5 -10 7 M inferred from abundance matching of the (sub)halo mass function to the observed galaxy mass function increase by a factor of ∼2. In addition, we find that an important fraction of low-mass subhaloes are completely devoid of stars. Accounting for the presence of dark subhaloes below 10 10 M further reduces the abundance of observable objects and leads to an additional increase in the inferred stellar-to-total mass ratio by factors of 2-10 for galaxies in haloes of 10 9 -10 10 M . This largely reconciles the abundance matching results with the kinematics of individual dwarf galaxies in CDM. We propose approximate corrections to the masses of objects derived from pure dark matter calculations to account for baryonic effects.

Exploring the liminality: properties of haloes and subhaloes in borderlinef(R) gravity

“…White 2001;Sawala et al 2013). In the above, to make comparison with the Sheth-Tormen formulae, we have used FOF haloes.…”

The early days of the Sculptor dwarf spheroidal galaxy

“…Teyssier et al 2013); to the "too big to fail problem", which raises questions about the matching between dark matter halos and their stellar masses (e.g. Boylan-Kolchin et al 2011, Sawala et al 2013; to the nature of dark matter (e.g. Governato et al 2015); and to the identification of the sources that were able to reionize the universe (e.g.…”

Subhalo demographics in the Illustris simulation: effects of baryons and halo-to-halo variation

“…This result is not shared by other hydrodynamic simulations. For example, Sawala et al (2013) found from the hydrodynamical simulation GIMIC (Crain et al 2009) that baryons reduce the mass of subhaloes less massive than 10 12 M , and the relative subhalo masses varies monotonically between 0.65 and 1 for subhaloes of mass 10 9 M and 10 14 M respectively. Additionally, the subhalo abundance is suppressed in GIMIC at small halo masses but never exceeds the N -body run for large halo masses.…”