In several jetted AGNs, structured jets have been observed. In particular spine-sheath configurations where the jet is radially divided into two or more zones of different flow velocities. We present ...a model based on the particle and radiation transport code CR-ENTREES. Here, interaction rates and secondary particle and photon yields are pre-calculated by Monte Carlo event generators or semi-analytical approximations. These are then used to create transition matrices, that describe how each particle spectrum evolves with time. This code allows for arbitrary injection of primary particles, and the possibility to choose which interaction to include (photo-meson production, Bethe-Heitler pair-production, inverse-Compton scattering, \(\gamma\)-\(\gamma\) pair production, decay of all unstable particles, synchrotron radiation -- from electrons, protons, and all relevant secondaries before their respective decays -- and particle escape). In addition to the particle and radiation interactions taking place in each homogeneous zone, we implement the feedback between the two zones having different bulk velocities. The main mechanism at play when particles cross the boundary between the two zones is shear acceleration. We follow a microscopic description of this acceleration process to create a corresponding transition matrix and include it in our numerical setup. Furthermore, each zone's radiation field can be used as an external target photon field for the other zone's particle interactions. We present here the first results of the effect of a two-zone spine-sheath jet, by applying this model to typical low-luminosity AGNs.
This study comprehensively investigates the gamma-ray dim population of
Fanaroff-Riley Type 0 (FR0) radio galaxies as potentially significant sources
of ultra-high-energy cosmic rays (UHECRs, E $>$ ...10$^{18}$ eV) detected on
Earth. While individual FR0 luminosities are relatively low compared to the
more powerful Fanaroff-Riley Type 1 and Type 2 galaxies, FR0s are substantially
more prevalent in the local universe, outnumbering the more energetic galaxies
by a factor of $\sim$5 within a redshift of z $\leq$ 0.05.
Employing CRPropa3 simulations, we estimate the mass composition and energy
spectra of UHECRs originating from FR0 galaxies for energies above 10$^{18.6}$
eV. This estimation fits data from the Pierre Auger Observatory (Auger) using
three extensive air shower models; both constant and energy-dependent observed
elemental fractions are considered. The simulation integrates an isotropic
distribution of FR0 galaxies, extrapolated from observed characteristics, with
UHECR propagation in the intergalactic medium, incorporating various plausible
configurations of extragalactic magnetic fields, both random and structured. We
then compare the resulting emission spectral indices, rigidity cutoffs, and
elemental fractions with recent Auger results. In total, 25 combined energy
spectrum and mass composition fits are considered.
Beyond the cosmic ray fluxes emitted by FR0 galaxies, this study predicts the
secondary photon and neutrino fluxes from UHECR interactions with intergalactic
cosmic photon backgrounds. The multi-messenger approach, encompassing
observational data and theoretical models, helps elucidate the contribution of
low luminosity FR0 radio galaxies to the total cosmic ray energy density.
FR0 galaxies constitute the most abundant jet population in the local
Universe. With their compact jet structure, they are broadband photon emitters
and have been proposed as multi-messenger sources. ...Recently, these sources have
been detected for the first time in $\gamma$ rays. Using a revised FR0 catalog,
we confirm that the FR0 population as a whole are $\gamma$-ray emitters, and we
also identify two significant sources. For the first time, we find a
correlation between the 5 GHz core radio luminosity and $\gamma$-ray luminosity
in the 1 - 800 GeV band, having a 4.5$\sigma$ statistical significance. This is
clear evidence that the jet emission mechanism is similar in nature for FR0s
and the well-studied canonical FR (FRI and FRII) radio galaxies. Furthermore,
we perform broadband SED modeling for the significantly detected sources as
well as the subthreshold source population using a one-zone SSC model. Within
the maximum jet power budget, our modeling shows that the detected gamma rays
from the jet can be explained as inverse Compton photons. To explain the
multi-wavelength observations for these galaxies, the modeling results
stipulate a low bulk Lorentz factor and a jet composition far from
equipartition, with the particle energy density dominating over the magnetic
field energy density.
We present a procedure to generally constrain the environments of neutrino-producing sites in photomeson production models of jetted Active Galactic Nuclei (AGN) where any origin of the dominant ...target photon field can be accommodated. For this purpose we reconstruct the minimum target photon spectrum required to produce the (observed) neutrino spectrum, and derive the distributions of all corresponding secondary particles. These initiate electromagnetic cascades with an efficiency that is linked to the neutrino production rate. The derived photon spectra represent the minimum radiation emerging from the source that is strictly associated with the photo-hadronically produced neutrinos. Using the 2014-15 neutrino spectrum observed by IceCube from TXS 0506+056, we conduct a comprehensive study of these cascade spectra and compare them to the simultaneous multi-wavelength emission. For this set of observations, photopion production from a co-spatially produced (co-moving) photon target can be ruled out as well as a setup where synchrotron or Compton-synchrotron supported cascades on a stationary (AGN rest frame) target photon field operate in this source. However, a scenario where Compton-driven cascades develop in the stationary soft-X-ray photon target which photo-hadronically produced the observed neutrinos appears feasible with required proton kinetic jet powers near the Eddington limit. The source is then found to produce neutrinos inefficiently, and emits GeV photons significantly below the observed Fermi-LAT-flux. Hence, the neutrinos and the bulk of the gamma rays observed in 2014/2015 from TXS 0506+056 cannot have been initiated by the same process.
The non-thermal spectra of jetted active galactic nuclei show a variety of shapes in their low- and high energy components. In some of the brightest Fermi-LAT blazars, prominent spectral breaks at a ...few GeV have been regularly detected, which is inconsistent with conventional cooling effects. We study the effects of continuous time-dependent injection of electrons into the jet with differing rates, durations, locations, and power-law spectral indices, and evaluate its impact on the ambient emitting particle spectrum at a given snapshot time in the framework of a leptonic blazar emission model. The emitting electron spectrum is calculated by Compton cooling the continuously injected electrons, where target photons are assumed to be provided by the accretion disk and broad line region. We calculate the non-thermal photon spectra produced by inverse Compton scattering of these external target radiation fields using the full Compton cross-section in the head-on approximation. By means of a comprehensive parameter study we present the resulting ambient electron and photon spectra, and discuss the influence of each injection parameter. Varying the injection parameters has a notable influence on the spectral shapes, which can be used to set constraints on the injection scenarios. We apply our model to the flare state spectral energy distribution of 3C454.3, and to the FSRQ PKS1510-089. For both sources we show two different model fits, corresponding to different injection scenarios. In all four injection scenarios impulsive particle injection is disfavored. Our model aims towards bridging jet emission with acceleration models using a phenomenological approach. Blazar spectral data can be analyzed with this model to constrain injection parameters, in addition to the conventional parameter values of steady-state emission models, if sufficient broad multifrequency coverage is provided.
We present a new energy transport code that models the time dependent and non-linear evolution of spectra of cosmic-ray nuclei, their secondaries, and photon target fields. The software can inject an ...arbitrary chemical composition including heavy elements up to iron nuclei. Energy losses and secondary production due to interactions of cosmic ray nuclei, secondary mesons, leptons, or gamma-rays with a target photon field are available for all relevant processes, e.g., photo-meson production, photo disintegration, synchrotron radiation, Inverse Compton scattering, and more. The resulting x-ray fluxes can be fed back into the simulation chain to correct the initial photon targets, resulting in a non-linear treatment of the energy transport. The modular structure of the code facilitates simple extension of interaction or target field models. We will show how the software can be used to improve predictions of observables in various astrophysical sources such as jetted active galactic nuclei (AGN). Since the software can model the propagation of heavy ultrahigh-energy cosmic rays inside the source it can precisely predict the chemical composition at the source. This will also refine predictions of neutrino emissions - they strongly depend on the chemical composition. This helps in the future to optimize the selection and analyses of data from the IceCube neutrino observatory with the aim to enhance the sensitivity of IceCube and reduce the number of trial factors.
A standard planetary nebula stays more than 10 000 years in the state of a photoionized nebula. As long as the timescales of the most important ionizing processes are much smaller, the ionization ...state can be characterized by a static photoionization model and simulated with codes like CLOUDY (Ferland et al. 1998). When the star exhibits a late helium flash, however, its ionizing flux stops within a very short period. The star then re-appears from its opaque shell after a few years (or centuries) as a cold giant star without any hard ionizing photons. Describing the physics of such behavior requires a fully time-dependent radiative transfer model. Pollacco (1999), Kerber et al. (1999) and Lechner & Kimeswenger (2004) used data of the old nebulae around V605 Aql and V4334 Sgr to derive a model of the pre-outburst state of the CSPN in a static model. Their argument was the long recombination time scale for such thin media. With regard to these models Schönberner (2008) critically raised the question whether a significant change in the ionization state (and thus the spectrum) has to be expected after a time of up to 80 years, and whether static models are applicable at all.
Fanaroff-Riley (FR) 0 radio galaxies form a low-luminosity extension to the well-established ultra-high-energy cosmic-ray (UHECR) candidate accelerators FR-1 and FR-2 galaxies. Their much higher ...number density -- up to a factor five times more numerous than FR-1 with \(z\leq 0.05\) -- makes them good candidate sources for an isotropic contribution to the observed UHECR flux. Here, the acceleration and survival of UHECR in prevailing conditions of the FR-0 environment are discussed. First, an average spectral energy distribution (SED) is compiled based on the \textit{FR0CAT}. These photon fields, composed of a jet and a host galaxy component, form a minimal target photon field for the UHECR, which will suffer from electromagnetic pair production, photo-disintegration, photo-meson production losses, and synchrotron radiation. The two most promising acceleration scenarios based on Fermi-I order and gradual shear acceleration are discussed as well as different escape scenarios. When an efficient acceleration mechanism precedes gradual shear acceleration, e.g., Fermi-I or others, FR-0 galaxies are likely UHECR accelerators. Gradual shear acceleration requires a jet Lorentz factor of \(\Gamma>1.6\), to be faster than the corresponding escape. In less optimistic models, a contribution to the cosmic-ray flux between the knee and ankle is expected to be relatively independent of the realized turbulence and acceleration.
The interaction between the strong winds in stellar colliding-wind binary (CWB) systems produces two shock fronts, delimiting the wind collision region (WCR). There, particles are expected to be ...accelerated mainly via diffusive shock acceleration (DSA). We investigate the injection and the acceleration of protons in typical CWB systems by means of Monte Carlo simulations, with both a test-particle approach and a non-linear method modelling a shock locally modified by the backreaction of the accelerated protons. We use magnetohydrodynamic simulations to determine the background plasma in the WCR and its vicinity. This allows us to consider particle acceleration at both shocks, on either side of the WCR, with a realistic large-scale magnetic field. We highlight the possible effects of particle acceleration on the local shock profiles at the WCR. We include the effect of magnetic field amplification due to resonant streaming instability (RSI), and compare results without and with the backreaction of the accelerated protons. In the latter case we find a lower flux of the non-thermal proton population, and a considerable magnetic field amplification. This would significantly increase the synchrotron losses of relativistic electrons accelerated in CWB systems, lowering the maximal energy they can reach and strongly reducing the inverse Compton fluxes. As a result, \(\gamma\)-rays from CWBs would be predominantly due to the decay of neutral pions produced in nucleon-nucleon collisions. This might provide a way to explain why, in the vast majority of cases, CWB systems have not been identified as \(\gamma\)-ray sources, while they emit synchrotron radiation.
This thesis will cover the process that I, Anita Reimer, have completed as part of my thesis role of Viola in Shakespeare's Twelfth Night . This thesis is divided into four main sections. The first ...section, "Preparation," is the research portion of my thesis. The first chapter is an overview of the foundational research. The second chapter consists of an analysis of the play including the storyline, comedic style, structure, and setting. Chapter three covers the characterization of Viola as played by myself, Anita Reimer. It includes Viola's personality traits and physical and vocal attributes as exemplified in the script. Also included in this chapter are the discoveries, objectives, obstacles, and risks of every scene that Viola is in, as well as Viola's relationships with the other characters in Twelfth Night . The second section, "Process," covers the performance aspect of this thesis. The third section is the "Production Product," which will consist of evaluations from theatre critics, faculty critics, and a personal critique. The final section consists of a series of appendices. (Abstract shortened by UMI.)
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