Astrophysics

The standard models of particle physics and cosmology predict the existence of a cosmological magnetic field. Estimates of the magnetic field strength and coherence scale are derived from MHD simulations and new MHD invariants. Such magnetic fields are consistent with upper and lower bounds obtained from various cosmological observations.

Quasars - accreting super-massive black holes - are the most luminous non-transient sources known and can be seen at redshifts of z > 7, when the Universe was just ~5% of its current age.  This implies that black holes with masses of up to ~10^9 M_Sun formed less than 800 Myr after the Big Bang, impossible under the default paradigm of Eddington-limited accretion onto stellar mass black holes.  The greatest barrier to understanding the formation and growth of these objects is the lack of data: quasars are very rare at these distances/times with fewer than ten known with z > 7 at present.  I will report on recent observational developments in this field, with a particular focus on the early results from the Euclid mission, for which the Wide Survey has the necessary combination of area, wavelength coverage and depth to increase the number of known quasars by an order of magnitude and to push to redshifts z > 8 and beyond.

We are now firmly within the ALMA-inspired era of star formation studies. We have abundant high sensitivity and resolution observations of star-disk-outflow systems as well as the ability to perform complex high-resolution plasma astrophysics simulations of their formation. I review recent three-dimensional nonideal MHD simulations that reveal surprising new insights into the role of magnetic fields and magnetic field dissipation in creating outflows, arcs, and cavities on scales of hundreds to thousands of au. Magnetic fields are responsible for a complex inflow-outflow structure around a protostar. I end the talk with results that may answer the longstanding big question in star formation studies: what stops the mass infall on to a protostar?