Reionization and the Abundance of Galactic Satellites

By James S. Bullock, Andrey V. Kravtsov, D. Weinberg. 2000

715 citations recorded by the source corpus.

One of the main challenges facing standard hierarchical structure formation models is that the predicted abundance of Galactic subhalos with circular velocities vc ~ 10-30 km s-1 is an order of magnitude higher than the number of satellites actually observed within the Local Group. Using a simple model for the formation and evolution of dark halos, based on the extended Press-Schechter formalism and tested against N-body results, we show that the theoretical predictions can be reconciled with observations if gas accretion in low-mass halos is suppressed after the epoch of reionization. In this picture, the observed dwarf satellites correspond to the small fraction of halos that accreted substantial amounts of gas before reionization. The photoionization mechanism naturally explains why the discrepancy between predicted halos and observed satellites sets in at vc ~ 30 km s-1, and for reasonable choices of the reionization redshift (zre ~ 5-12) the model can reproduce both the amplitude and shape of the observed velocity function of galactic satellites. If this explanation is correct, then typical bright galaxy halos contain many low-mass dark matter subhalos. These might be detectable through their gravitational lensing effects, through their influence on stellar disks, or as dwarf satellites with very high mass-to-light ratios. This model also predicts a diffuse stellar component produced by large numbers of tidally disrupted dwarfs, perhaps sufficient to account for most of the Milky Way's stellar halo.

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Citations in the corpus

The Progenitors of Dwarf Spheroidal Galaxies (2002, background): “Such a process may have occurred during the re-ionization of the universe, potentially cutting off the supplies of gas for star formation in dwarf galaxies (see Thoul & Weinberg 1996; Barkana & Loeb 1999; Bullock et al. 2000).”
The New Galaxy: Signatures of Its Formation (2002, background): “Many authors note that the accretion of gas on to low-mass halos and subsequent star formation is heavily suppressed in the presence of a strong photoionizing background (Ikeuchi 1986; Rees 1986; Babul & Rees 1992; Bullock et al. 2000).”
The Phenomenology of Right Handed Neutrinos (2013, background): “[487–490], though this may not explain the discrepancy for objects that are too big to fail to attract gas, see e.”
The Dependence of Halo Clustering on Halo Formation History, Concentration, and Occupation (2005, background): “It has been suggested (Bullock et al. 2000) that the discrepancy between the abundance of dwarf satellites observed in the Local Group and the abundance of relevant dwarf-mass dark halos (vmaxP 50 km s 1) expected by CDM can be resolved by suppressing galaxy formation in halos that form after the…”
Resolving the Structure of Cold Dark Matter Halos (2000, background): “Halos of a given mass will have lower concentration (see Bullock et al. 2000).”
Mass loss of galaxies due to an ultraviolet background (2008, methodology): “The relation Mc = MF proposed by Gnedin is often used in semianalytic modelling for dwarf galaxy formation in order to describe the quenching of star formation (Bullock et al. 2000; Benson et al. 2002a,b; Somerville 2002).”
The Origin of Dwarf Ellipticals in the Virgo Cluster (2008, background): “…number density is still significantly smaller than predicted by hierarchical models of galaxy formation for the field luminosity function (Kauffmann et al. 1993; Cole et al. 1994; Somerville & Primack 1999, Nagashima et al. 2005) or for the local group (Klypin et al. 1999; Bullock et al. 2000).”
Forged in FIRE: cusps, cores and baryons in low-mass dwarf galaxies (2015, unknown): “G A ] ing background (Dekel & Silk 1986; Bullock et al. 2000).”
Formation and Evolution of Galaxy Dark Matter Halos and Their Substructure (2007, methodology): “Similar models (Bullock et al. 2000; Moore et al. 2006) select only systems above the atomic cooling mass at the reionisation epoch (z ≃ 10).”
Luminosity function and radial distribution of Milky Way satellites in a ΛCDM Universe (2009, result): “…studies showed quantitatively that this suppression of gas infall by cosmic reionization could plausibly reconcile the observed and predicted numbers of “classical” Local Group satellites (Bullock et al. 2000, Somerville 2002, Ricotti, Gnedin & Shull 2002, Benson et al. 2002, Read et al. 2006).”