Satellite Energy Research Articles

Is there substructure around M87?

We present a general method to identify infalling substructure in discrete datasets with position and line-of-sight velocity data. We exploit the fact that galaxies falling onto a brightest cluster galaxy (BCG) in a virialised cluster, or dwarf satellites falling onto a central galaxy like the Milky Way, follow nearly radial orbits. If the orbits are exactly radial, we show how to find the probability distribution for a satellite's energy, given a tracer density for the satellite population, by solving an Abel integral equation. This is an extension of Eddington (1916)'s classical formula for the isotropic distribution function. When applied to a system of galaxies, clustering in energy space can then be quantified using the Kullback-Leibler divergence, and groups of objects can be identified which, though separated in the sky, may be falling in on the same orbit. This method is tested using mock data and applied to the satellite galaxy population around M87, the BCG in Virgo, and a number of associations are found which may represent infalling galaxy groups.

Simulating sinking satellites with superbox-10

SUPERBOX-10 is the successor of SUPERBOX, a particle-mesh code where additional grids and sub-grids are applied to regions of high particle density. Previous limitations have been solved. For instance, the vertical resolution is improved considerably when flattened grids are used. Since the computationally most intensive part is the Fast Fourier Transform, we introduce a parallelised version using the library FFTW, resulting in a speed-up of a few. The new features are tested using a galaxy model consisting of an exponential disc, a bulge and a dark matter halo. We demonstrate that the use of flattened grids efficiently reduces numerical heating. We simulate the merging of disc-bulge-halo galaxies with small spherical satellites. As a result, satellites on orbits with both low eccentricity and inclination heat the disc most efficiently. Moreover, we find that most of the satellite's energy and angular momentum is transfered to the halo.

Shake-up valence excitations inCuOby resonant inelastic x-ray scattering

Shake-up satellites are found in the resonant inelastic x-ray scattering spectra of $\mathrm{CuO}$ single crystals, excited by means of monochromatized synchrotron radiation with energies near the $\mathrm{Cu}$ $K$-edge. Within the limits of third-order perturbation treatment, the satellites are attributed to charge transfer excitations between a bonding ${b}_{1g}$ ground state and antibonding states of ${a}_{1g},$ ${b}_{2g},$ ${b}_{1g}$, and ${e}_{g}$ symmetry. These transitions are induced by Coulomb interaction of the $\underset{}{1s}$-hole, which constitutes the intermediate state of the resonant inelastic x-ray scattering process, with the $\mathrm{Cu}$ $3d$ system. We have modeled the dependence of the satellite's energy loss position on the incident photon energy by means of a third-order perturbation treatment, where two different $\mathrm{Cu}$ $\underset{}{1s}3{d}^{9}\phantom{\rule{0.3em}{0ex}}4p$ excitations constituting the resonant inelastic x-ray scattering process must be taken into account. Together with a dipole forbidden $\underset{}{1s}3{d}^{10}$ and a dipole allowed $\underset{}{1s}3{d}^{10}\underset{}{L}4p$ transition, another dipole allowed $\mathrm{Cu}$ $\underset{}{1s}3{d}^{9}4p$ excitation was investigated in detail by means of resonantly excited $\underset{}{1s}2p$ $({K}_{\ensuremath{\alpha}})$ emission, especially with respect to its dependence on incident polarization. Since this excitation does not leave behind a trace in conventional x-ray absorption spectra, symmetry assignment can be obtained only this way. An investigation of the dependence of the satellite's intensity on the scattering angle in vertical and horizontal scattering geometry has stressed the necessity to take into account the polarization and scattering angle dependence of the resonant elastic scattering process, being composed of the production and recombination of the virtual $\underset{}{1s}4p$ exciton, when it is regarded to be decoupled from the $\mathrm{Cu}$ $3d$ system.