Investigating the nature of dark matter with strong gravitational lensing by Daniel Gilman
Strong gravitational lensing by galaxies provides a powerful, direct, and elegant method to infer the properties of dark matter structure below 10^8 solar masses, where halos are almost completely devoid of stars and gas. As various dark matter models make unique predictions for the halo mass function and concentration-mass relation in this regime, structure formation inferences from lensing can be cast as constraints on the nature of dark matter itself. I will describe a forward modeling framework that constrains any structure formation model based on dark matter theory using the flux ratios in a sample of quadruple image strong lenses. I will highlight recent applications of this method to constrain the free-streaming length of warm dark matter, and the concentration-mass relation of cold dark matter halos on sub-galactic scales.
A new conservation law for Planetary Impacts by Almog Yalinewich
Terrestrial planets are constantly bombarded by bodies of widely different sizes and masses. Such impacts can release energies exceeding those of hydrogen bombs, level forests, destroy civilisations, cause mass extinctions and deplete atmospheres. In this talk I will present a new universal analytic solution that can describe the shock wave in all these scenarios. I will show that this shock wave satisfies a new kind of conservation law that lies somewhere in between energy and momentum conservation. I will show how this new conservation law can explain a number of features related to impact phenomenology, including sizes of craters, extent of the blast zone of the 2013 Chelyabinsk fireball and atmospheric mass loss.
Daniel Gilman, DADDAA; Almog Yalinewich, CITA
February 24, 2021
2:00 pm - 3:00 pm