| Black hole factories: exploring the origins of supermassive black holes using the Renaissance Simulations |
| Brian O'Shea |
| Department of Physics and Astronomy, Michigan State University, USA |
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Supermassive black holes are observed at the centers of all large galaxies, and also at surprisingly early times in the universe. This latter property – where black holes of more than 108 solar masses are observed less than a billion years after the Big Bang – presents significant challenges to our understanding of cosmological structure formation and black hole growth in the early Universe. In this talk, I present two related efforts to understand the growth of supermassive black holes in the early universe using the Renaissance Simulations, a set of physics-rich calculations of cosmological structure formation that give us the unprecedented ability to study the growth of the progenitors of these objects. I explore the feasibility of the two most common formation scenarios – the rapid growth of ~10 solar mass black holes coming from the death of massive stars, and the formation of much larger supermassive black hole progenitors in an environment that facilitates the direct collapse of large gas clouds into a black hole. I will present a novel formation path for the "direct collapse" scenario that emerges from the broad range of galaxy formation histories probed by the Renaissance Simulations |
| Correlations and energy transfer in compressible isothermal and adiabatic MHD turbulence |
| Philipp Grete |
| Department of Physics and Astronomy, Michigan State University, USA |
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Compressibility, magnetic fields and turbulence are all thought to be important factors to varying degrees in many astrophysical processes and terrestrial experiments. However, our understanding of their joint effect, even in its simplest description (i.e., compressible magnetohydrodynamic turbulence), is still scarce. One step towards a more comprehensive picture is a better understanding of the governing energy dynamics, e.g., looking at the interplay between kinetic and magnetic energy via different mediators such as advection, magnetic tension or magnetic pressure. Here, we present an extension of established shell-to-shell energy transfer analysis methods to the compressible MHD regime. We apply this analysis to numerical simulations in both the subsonic and supersonic regimes. This allows us to illustrate how varying degrees of compressibility influence the energy dynamics within and between kinetic and magnetic energy reservoirs. For example, we show that compression acts against a magnetic energy cascade (scale-local magnetic to magnetic energy transfer). Moreover, we present how magnetic tension becomes overall less important with increasing sonic Mach number. Finally, we show how different correlations, such as the observationally relevant correlation between density and magnetic field strength, are affected by different equations of state. |