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Journal-club Doctorants / Journal-club PhD students

« AGN in dwarf galaxies »

Gohar Dashyan
Institut d'Astrophysique de Paris (Paris, France)

In the cold dark matter (CDM) cosmological model, larger structures form through successive mergers. Therefore, dwarf galaxies are potentially left over of buildings blocks of galaxies and provide a test bed for the CDM model, as the smallest probes of cosmological structure formation. The LambdaCDM model has proven successful at reproducing the large scale universe, however, disparities exist between the theory and observations on small scales: the model predicts too many small galaxies (the so-called "missing satellites" problem) and cuspy dark matter profiles that are not yet convincingly observed, and the most massive dwarfs predicted by LambdaCDM simulations are rarely observed. Baryonic feedback, especially supernovae feedback may be a resolution to all these difficulties. Ram pressure stripping, tidal stripping, harassment, are alternative or complementary mechanisms. It is, however, still not clear whether these mechanisms can reconcile theory and observations at the low mass end of the galaxy luminosity function. The role of supernovae feedback is uncertain since supernovae might fail in multiphase interstellar medium (ISM). Moreover, massive dwarf galaxies seem to require stronger feedback than supernovae can provide. The role of environmental physics is also uncertain, since dwarf galaxies disagreement with the standard model seems to extend to regions where environmental effects should be small.

In this work, we analytically explore the possibility feedback from Active Galactic Nuclei (AGN) in dwarf galaxies in a simple model. Considering the presence of an intermediate mass black hole within low mass galaxies, we use simple scaling relations and model the propagation and properties of the blast wave to reveal a critical condition for global gas loss. Performing the same calculation for supernovae, we compare the ability of outflows from AGN and supernovae to drive gas out of galaxies.
mercredi 24 mai 2017 - 17:00
Salle Entresol Daniel Chalonge, Institut d'Astrophysique
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