Chris Nagele

Abstract GN-z11 is an unusually luminous high-redshift galaxy that was recently observed to have strong nitrogen lines while at the same time lacking traditional signatures of active galactic nucleus activity. These observations have been interpreted as a supersolar nitrogen abundance, which is challenging to explain with standard stellar evolution and supernova enrichment. We present simulations of four models of metal-enriched supermassive stars after the zero age main sequence, which produce

ABSTRACT Observed supermassive black holes in the early Universe have several proposed formation channels in part because most of these channels are difficult to probe. One of the more promising channels, the direct collapse of a supermassive star has several possible probes including the explosion of a helium-core supermassive star triggered by a general relativistic instability. We develop a straightforward method for evaluating the general relativistic radial instability without simplifying a

ABSTRACT We investigate the possibility of a supernova in supermassive (5 × 104 M⊙) population III stars induced by a general relativistic instability occurring in the helium burning phase. This explosion could occur via rapid helium burning during an early contraction of the isentropic core. Such an explosion would be visible to future telescopes and could disrupt the proposed direct collapse formation channel for early Universe supermassive black holes. We simulate first the stellar evolution

ABSTRACT The assembly of supermassive black holes poses a challenge primarily because of observed quasars at high redshift, but additionally because of the current lack of observations of intermediate mass black holes. One plausible scenario for creating supermassive black holes is direct collapse triggered by the merger of two gas-rich galaxies. This scenario allows the creation of supermassive stars with solar metallicity. We investigate the behaviour of metal enriched supermassive stars which

ABSTRACT The origin of high-redshift quasars and their supermassive black hole engines is unclear. One promising solution is the collapse of a primordial supermassive star. Observational confirmation of this scenario may be challenging, but a general relativistic instability supernova provides one avenue for such. Previous studies have found that a general relativistic instability supernova has a potentially decades-long plateau phase visible to JWST at high redshift. In this work, we examine st

We study the dynamics of the massive Schwinger model on a lattice using exact diagonalization. When periodic boundary conditions are imposed, analytic arguments indicate that a nonzero electric flux in the initial state can ``unwind'' and decrease to a minimum value equal to minus its initial value, due to the effects of a pair of charges that repeatedly traverse the spatial circle. Our numerical results support the existence of this flux unwinding phenomenon, both for initial states containing

The formation of supermassive black holes and their progenitors is an outstanding problem in astrophysics. The authors examine one progenitor scenario where these black holes form from the unstable collapse of supermassive stars. Running both hydrostatic and hydrodynamic calculations that account for the effects of general relativity, accretion and nuclear burning, they show that for much of parameter space, these accreting supermassive stars do not collapse, but rather explode dues to nuclear e

ABSTRACT We calculate the neutrino signal from Population III supermassive star (SMS) collapse using a neutrino transfer code originally developed for core-collapse supernovae and massive star collapse. Using this code, we are able to investigate the SMS mass range thought to undergo neutrino trapping (∼104 M⊙), a mass range which has been neglected by previous works because of the difficulty of neutrino transfer. For models in this mass range, we observe a neutrino sphere with a large radius an

Abstract We study quantum decoherence numerically in a system consisting of a relativistic quantum field theory coupled to a measuring device that is itself coupled to an environment. The measuring device and environment are treated as quantum, non-relativistic particles. We solve the Schrödinger equation for the wave function of this tripartite system using exact diagonalization. Although computational limitations on the size of the Hilbert space prevent us from exploring the regime where the d

Abstract The conditions under which galactic nuclear regions become active are largely unknown, although it has been hypothesized that secular processes related to galaxy morphology could play a significant role. We investigate this question using optical i -band images of 3096 SDSS quasars and galaxies at 0.3 < z < 0.6 from the Hyper Suprime-Cam Subaru Strategic Program, which possesses a unique combination of area, depth, and resolution, allowing the use of residual images, after removal

Abstract SN2018ibb is a recently observed hydrogen-poor superluminous supernova that appears to be powered by the decay of 30 M ⊙ of radioactive nickel. This supernova has been suggested to show hybrid signatures of a pair-instability supernova and an interacting supernova. In a previous paper, we found that rotating, metal-enriched pair-instability supernova progenitors appeared to check both of these boxes. In this paper, we model the lightcurves of the pair-instability supernovae using STELLA

SN2018ibb is a recently observed hydrogen poor super-luminous supernova which appears to be powered by the decay of $30\;\rm{M_\odot}$ of radioactive nickel. This supernova has been suggested to show hybrid signatures of a pair instability supernova and an interacting supernova. In a previous paper, we found that rotating, metal enriched pair instability supernova progenitors appeared to check both of these boxes. In this paper, we model the lightcurves of the pair instability supernovae using S

In recent years, the formation and evolution of rapidly accreting supermassive stars has received significant attention in the hope of better understanding the origin of high redshift quasars. It is often taken for granted that once formed, these supermassive stars will encounter the general relativistic radial instability and collapse to form massive black holes. Here, we present the first ever general relativistic hydrodynamical simulations of the collapse of rapidly accreting supermassive sta

The assembly of supermassive black holes poses a challenge primarily because of observed quasars at high redshift, but additionally because of the current lack of observations of intermediate mass black holes. One plausible scenario for creating supermassive black holes is direct collapse triggered by the merger of two gas rich galaxies. This scenario allows the creation of supermassive stars with solar metallicity, where the enhanced metallicity is enabled by extremely rapid accretion. We inves