12:00–1:00 pm ERC 501
Host: Vikram Dwarkadas
Luca Orusa (University of Torino) "A multi-messenger approach in the study of cosmic ray positrons"
The positron flux in cosmic rays is currently measured with unprecedented precision by AMS-02 up to TeV energies. The interpretation of the spectra is still debated, especially for the excess of positrons above 10 GeV, that deviates from the predictions of the secondary flux, generated by the interaction of cosmic rays with the interstellar medium. The hypothesis that pulsars can significantly contribute to this excess has been consolidated after the observation of gamma-ray halos by HAWC and LHAASO at TeV energies around several pulsars. These halos can be explained by the inverse Compton scattering on the interstellar radiation fields performed by leptons injected from these sources. I will describe how we can use the high-precision AMS-02 positron data to constrain the main properties of the Galactic pulsar population. I will describe how it is possible to infer information from TeV gamma-ray halos on the particle production efficiency of pulsars and on the diffusion process around these sources. In the end I will show how it is possible to reduce the uncertainties on the secondary flux predictions thanks to the measurements of cross sections preformed by collider experiments.
Georgios Zacharegkas (UChicago) "Bridging the gap between large-scale cosmology and small-scale astrophysics"
In our standard cosmological paradigm, galaxies form inside of dark matter halos. As a result, the distribution of galaxies in the Universe closely traces the distribution of dark matter, and the properties of dark matter halos are tightly connected to the properties of the galaxies they host. The study of this relation is often referred to as the galaxy-halo connection, and it plays a key role in understanding galaxy formation and cosmology. I will talk about my work that utilizes the Halo Occupation Distribution (HOD) framework to model the galaxy-halo connection in the Year 3 of the Dark Energy Survey (DES Y3). I will also talk about extensions of this work to cosmological studies and more.
