Two can play at that game: constraining the role of supernova and AGN feedback in dwarf galaxies with cosmological zoom-in simulations

Kavli Affiliate: Debora Sijacki

| First 5 Authors: Sophie Koudmani, Debora Sijacki, Matthew C. Smith, ,

| Summary:

There is growing observational evidence for dwarf galaxies hosting active
galactic nuclei (AGN), including hints of AGN-driven outflows in dwarfs.
However, in the common theoretical model of galaxy formation, efficient
supernova (SN) feedback is the tool of choice for regulating star formation in
the low-mass regime. In this paper, we present a suite of high-resolution
cosmological dwarf zoom-in simulations relaxing the assumption of strong SN
feedback, with the goal to determine whether more moderate SN feedback in
combination with an efficient AGN could be a suitable alternative. Importantly,
we find that there are sufficient amounts of gas to power brief
Eddington-limited accretion episodes in dwarfs. This leads to a variety of
outcomes depending on the AGN accretion model: from no additional suppression
to moderate regulation of star formation to catastrophic quenching. Efficient
AGN can drive powerful outflows, depleting the gas reservoir of their hosts via
ejective feedback and then maintaining a quiescent state through heating the
circumgalactic medium. Moderate AGN outflows can be as efficient as the strong
SN feedback commonly employed, leading to star formation regulation and HI gas
masses in agreement with observations of field dwarfs. All efficient AGN
set-ups are associated with overmassive black holes (BHs) compared to the
(heavily extrapolated) observed BH mass – stellar mass scaling relations, with
future direct observational constraints in this mass regime being crucially
needed. Efficient AGN activity is mostly restricted to high redshifts, with
hot, accelerated outflows and high X-ray luminosities being the clearest
tell-tale signs for future observational campaigns.

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