Abstract
Dwarf galaxy anomalies, such as their abundance and cusp-core problems, remain a prime challenge in our understanding of galaxy formation. The inclusion of baryonic physics could potentially solve these issues, but the efficiency of stellar feedback is still controversial. We analytically explore the possibility of feedback from Active Galactic Nuclei (AGN) in dwarf galaxies and compare AGN and supernova (SN) feedback. We assume the presence of an intermediate mass black hole within low mass galaxies and standard scaling relations between the relevant physical quantities. We model the propagation and properties of the outflow and explore the critical condition for global gas ejection. Performing the same calculation for SNe, we compare the ability of AGN and SNe to drive gas out of galaxies. We find that a critical halo mass exists below which AGN feedback can remove gas from the host halo and that the critical halo mass for AGN is greater than the equivalent for SNe in a significant part of the parameter space, suggesting that AGN could provide an alternative and more successful source of negative feedback than SNe, even in the most massive dwarf galaxies.
Highlights
In the cold dark matter (CDM) cosmological model, larger structures form through successive mergers
The CDM model has proven successful at reproducing the large scale Universe, disparities exist between the theory and observations on small scales: the model predicts too many small galaxies and cuspy dark matter profiles that are not yet convincingly observed (Oh et al 2011), and the most massive dwarfs predicted by CDM simulations are rarely observed
We investigated the possibility of AGN feedback in dwarf galaxies
Summary
In the cold dark matter (CDM) cosmological model, larger structures form through successive mergers. We compute the critical halo mass for gas expulsion out of the halo by the AGN outflow, following the example of Dekel & Silk (1986) for SNe. We examine how that critical mass depends on parameters, using standard scaling relations and a spherical model. We examine how that critical mass depends on parameters, using standard scaling relations and a spherical model This allows us to compare the roles of SNe and AGNs in expelling the gas. This is a different approach from the one yielding a high-mass break (Bower et al 2006; Croton et al 2006), which involves the role of an AGN in suppressing cooling flows on to massive galaxies, thereby modifying the bright end of the galaxy luminosity function. We use scaling relations to estimate the physical quantities (Section 2.1), with the aim of exploring the parameter space
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