Dwarf galaxies in voids: suppressing star formation with photoheating

By Matthias Hoeft, G. Yepes, Stefan Gottloeber, Volker Springel. 2005

258 citations recorded by the source corpus.

We study the structure formation in cosmological void regions using high-resolution hydrody-namical simulations. Despite being significantly underdense, voids are populated abundantly with small dark matter haloes which should appear as dwarf galaxies if their star formation is not suppressed significantly. We here investigate to which extent the cosmological ultraviolet (UV) background reduces the baryon content of dwarf galaxies, and thereby limits their cooling and star formation rates. Assuming a Haardt & Madau UV background with reionization at redshift z = 6, our samples of simulated galaxies show that haloes with masses below a characteristic mass of M c (z = 0) = 6.5 x 10 9 h -1 M ⊙ are baryon-poor, but in general not completely empty, because baryons that are in the condensed cold phase or are already locked up in stars resist evaporation. In haloes with mass M? M c , we find that photoheating suppresses further cooling of gas. The redshift- and UV-background-dependent characteristic mass M c (z) can be understood from the equilibrium temperature between heating and cooling at a characteristic overdensity of δ ≃ 1000. If a halo is massive enough to compress gas to this density despite the presence of UV-background radiation, gas is free to 'enter' the condensed phase and cooling continues in the halo, otherwise it stalls. By analysing the mass accretion histories of dwarf galaxies in voids, we show that they can build up a significant amount of condensed mass at early times before the epoch of reionization. Later on, the amount of mass in this phase remains roughly constant, but the masses of the dark matter haloes continue to increase. Consequently, photoheating leads to a reduced baryon fraction in void dwarf galaxies, endows them with a rather old stellar population, but still allows late star formation to some extent. We estimate the resulting stellar mass function for void galaxies. While the number of galaxies at the faint end is significantly reduced due to photoheating, additional physical feedback processes may be required to explain the apparent paucity of dwarfs in observations of voids.

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Citations in the corpus

FIRE in the field: Simulating the threshold of galaxy formation (2016, background): “…at which the baryon fraction of halos is reduced by 50% relative to the cosmic baryon fraction fb ≡ Ωb/Ωm (which is 0.168 for the cosmology we adopt in this paper, as detailed at the end of this section) owing to the cosmic UV background (Hoeft et al. 2006; Okamoto et al. 2008; Noh & McQuinn 2014).”
Cosmic Dawn (CoDa): the first radiation-hydrodynamics simulation of reionization and galaxy formation in the Local Universe (2015, background): “…(Shapiro et al. 2004; Iliev et al. 2005) and through the suppression of gas infall onto low-mass galaxies above the minihalo mass range, by photoheating the intergalactic gas and raising its pressure (Shapiro et al. 1994; Gnedin 2000; Hoeft et al. 2006), affecting their star formation efficiency.”
Mass loss of galaxies due to an ultraviolet background (2008, methodology): “For the same reasons, the agreement atz = 0 between a model by Hoeft et al. (2006) which compared the equilibrium temperature at high density (∆ = 1000) with Tvir (dashed line in Fig.”
Quenching and ram pressure stripping of simulated Milky Way satellite galaxies (2017, unknown): “The filtering halo mass for the effect of reionization is often assumed to be around 109 M because the virial temperature of haloes at this mass is similar to the IGM temperature (Gnedin 2000; Hoeft et al. 2006; Okamoto et al. 2008).”
Luminosity function and radial distribution of Milky Way satellites in a ΛCDM Universe (2009, methodology): “…results, by both varying the reionization redshift within our reference model based on Kravtsov et al. (2004) and by applying a simple modification to this model to take into account recent results based on high resolution hydrodynamical simulations (e.g. Okamoto et al. 2008; Hoeft et al. 2006).”
Sweating the small stuff: simulating dwarf galaxies, ultra-faint dwarf galaxies, and their own tiny satellites (2015, background): “…resolution is the main driver of their apparent halo mass limit for star formation, in general it has been the case that every time resolution is increased in simulations, the minimum virial mass for a halo that can form stars has approached lower values (Hoeft et al. 2006; Oñorbe et al. 2015).”