Growth and Feedback from the First Black Holes

Regardless of their initial seed mass, any active galactic nuclei observed at redshifts z > 6 must have grown by several orders of magnitude from their seeds. In this chapter, we will discuss the physical processes and latest research on black hole growth and associated feedback after seed formation. Fueling is initially slowed down by radiative feedback from the black hole itself and supernova explosions from nearby stars. Its growth however accelerates once the host galaxy grows past a critical mass.Comment: 30 pages, 6 figures. Preprint of a review volume chapter to be published in Latif, M., & Schleicher, D.R.G., "Growth and Feedback from the First Black Holes'', Formation of the First Black Holes, 2018. Copyright World Scientific Publishing Company, https://www.worldscientific.com/worldscibooks/10.1142/1065

How Very Massive Metal Free Stars Start Cosmological Reionization

(Abridged) Using ab initio cosmological Eulerian adaptive mesh refinement radiation hydrodynamical calculations, we discuss how very massive stars start the process of cosmological reionization. The models include non-equilibrium primordial gas chemistry and cooling processes and accurate radiation transport in the Case B approximation using adaptively ray traced photon packages, retaining the time derivative in the transport equation. Supernova feedback is modeled by thermal explosions triggered at parsec scales. All calculations resolve the local Jeans length by at least 16 grid cells at all times and as such cover a spatial dynamic range of ~10^6. These first sources of reionization are highly intermittent and anisotropic and first photoionize the small scales voids surrounding the halos they form in, rather than the dense filaments they are embedded in. As the merging objects form larger, dwarf sized galaxies, the escape fraction of UV radiation decreases and the HII regions only break out on some sides of the galaxies making them even more anisotropic. In three cases, SN blast waves induce star formation in overdense regions that were formed earlier from ionization front instabilities. These stars form tens of parsecs away from the center of their parent DM halo. Approximately 5 ionizing photons are needed per sustained ionization when star formation in 10^6 M_sun halos are dominant in the calculation. As the halos become larger than ~10^7 M_sun, the ionizing photon escape fraction decreases, which in turn increases the number of photons per ionization to 15-50, in calculations with stellar feedback only. Supernova feedback in these more massive halos creates a more diffuse medium, allowing the stellar radiation to escape more easily and maintaining the ratio of 5 ionizing photons per sustained ionization.Comment: 16 pages, 15 figures, accepted to ApJ. Final version. High resolution images and movies available at http://www.slac.stanford.edu/~jwise/research/Reionizatio