Hintze Centre for Astrophysical Surveys

Abstract:

The evolution of galaxies is known to be connected to their position within the large-scale structure and their local environmental density. We investigate the relative importance of these using the underlying dark matter density field extracted from the Constrained Simulations in BORG (CSiBORG) suite of constrained cosmological simulations. We define cosmic web environment through both dark matter densities averaged on a scale up to 16 Mpc , and through cosmic web location identified by applying DisPerSE to the CSiBORG haloes. We correlate these environmental measures with the properties of observed galaxies in large surveys using optical data (from the NASA-Sloan Atlas) and 21-cm radio data (from ALFALFA). We find statistically significant correlations between environment and colour, neutral hydrogen gas () mass fraction, star formation rate, and Sérsic index. Together, these correlations suggest that bluer, star-forming, rich, and disc-type galaxies tend to reside in lower density areas, further from filaments, while redder, more elliptical galaxies with lower star formation rates tend to be found in higher density areas, closer to filaments. We find analogous trends with the quenching of galaxies, but notably find that the quenching of low-mass galaxies has a greater dependence on environment than the quenching of high-mass galaxies. We find that the relationship between galaxy properties and the environmental density is stronger than that with distance to filament, suggesting that environmental density has a greater impact on the properties of galaxies than their location within the larger-scale cosmic web.

Abstract:

The origin of cosmic rays (CRs) from outside the Solar system is unknown, as they are deflected by the interstellar magnetic field. Supernova remnants are the main candidate for CRs up to PeV energies but due to lack of evidence, they cannot be concluded as the sources of the most energetic Galactic CRs. We investigate discrete ejecta produced in state transitions of black hole X-ray binary systems as a potential source of CRs, motivated by recent TeV -ray detections by LHAASO. Starting from MAXI J1820+070, we examine the multi-wavelength observations and find that efficient particle acceleration may take place (i.e. into a robust power law), up to eV, where is the ratio of particle energy to magnetic energy. From these calculations, we estimate the global contribution of ejecta to the entire Galactic spectrum to be , with the CR contribution rising to at PeV energies, assuming roughly equal energy in non-thermal protons, non-thermal electrons, and magnetic fields. In addition, we calculate associated -ray and neutrino spectra of the MAXI J1820+070 ejecta to investigate new detection methods with CTAO, which provide strong constraints on initial ejecta size of order Schwarzschild radii ( pc) assuming a period of adiabatic expansion.

Abstract:

Abstract We investigate the relationship between disc winds, radio jets, accretion rates and black hole masses of a sample of ∼100k quasars at z ≈ 2. Combining spectra from the 17th data release of the Sloan Digital Sky Survey (SDSS) with radio fluxes from the 2nd data release of the Low Frequency ARray (LOFAR) Two-Meter Sky Survey (LoTSS), we statistically characterise a radio loud and radio quiet population using a two-component Gaussian Mixture model, and perform population matching in black hole mass and Eddington fraction. We determine how the fraction of radio loud sources changes across this parameter space, finding that jets are most efficiently produced in quasars with either a very massive central black hole (MBH > 109M⊙) or one that is rapidly accreting (λEdd > 0.3). We also show that there are differences in the blueshift of the $\textrm {C}\, \rm \small {IV}$ λ1549Å line and the equivalent width of the $\rm {He}\, \rm \small {II}$ λ1640Å line in radio loud and radio quiet quasars that persist even after accounting for differences in the mass and accretion rate of the central black hole. Generally, we find an anti-correlation between the inferred presence of disc winds and jets, which we suggest is mediated by differences in the quasars’ spectral energy distributions. The latter result is shown through the close coupling between tracers of wind kinematics and the ionising flux– which holds for both radio loud and radio quiet sources, despite differences between their emission line properties– and is hinted at by a different Baldwin effect in the two populations.