Beecroft Institute for Particle Astrophysics and Cosmology

Abstract:

This contribution discusses the challenges of implementing star formation and stellar feedback processes in galaxy simulations. Insufficient computational power and numerous poorly understood physical processes, force simulations to adopt sub-grid models of the interstellar medium. These may crucially bias results. We advocate for smaller (similar to kiloparsec) scale simulations of the interstellar medium to guide the development of sub-grid models in larger simulations. In this vein, I show results on ever increasing scales ranging from similar to 1 h(-1) kpc(3) ISM simulations, to a 1 h(-1) Mpc(3) simulation of a galaxy forming at evolved high redshift, to a larger cosmological volume, 6.25 h(-1) Mpc(3), down to redshift 3. We find that galactic winds can be powered by SN implemented as point explosions in high redshift galaxies simulated with sufficient spatial resolution. Galaxies at lower redshift require alternative sub-grid feedback models and we present one possible solution to generate winds from galaxies at redshift similar to 4.

Abstract:

We combine the QSO samples from the 2dF QSO Redshift Survey (2QZ) and the 2dF-SDSS LRG and QSO Survey (2SLAQ) in order to investigate the clustering of z~1.4 QSOs and measure the correlation function. The clustering signal in z-space, projected along the sky direction, is similar to that previously obtained from 2QZ alone. By fitting the z-space correlation function and lifting the degeneracy between beta and Omega_m_0 by using linear theory predictions, we obtain beta(z=1.4) = 0.60+-0.12 and Omega_m_0=0.25+-0.08, implying a value for the QSO bias, b(z=1.4)=1.5+-0.2. We further find that QSO clustering does not depend strongly on luminosity at fixed redshift. This result is inconsistent with the expectation of simple `high peaks' biasing models where more luminous, rare QSOs are assumed to inhabit higher mass haloes. The data are more consistent with models which predict that QSOs of different luminosities reside in haloes of similar mass. We find that halo mass does not evolve strongly with redshift nor depend on QSO luminosity. We finally investigate how black hole mass correlates with luminosity and redshift and ascertain the relation between Eddington efficiency and black hole mass. Our results suggest that QSOs of different luminosities may contain black holes of similar mass.