Special Cosmology Seminar Double-Header

Ioana Zelko (CITA) and Xiaolong Du (Carnegie)
Friday, March 10, 2023
2:00 pm
NS2 2201

Ioana Zelko (CITA)

Title: Exploiting the Synergy between Cosmology and Galactic Science

I will describe my work in the fields of cosmology and galactic science, highlighting how both fields can work in tandem to make key discoveries in each other. The first segment will focus on the use of gravitational lensing by galaxies and their halos to provide insights into dark matter models. I will describe the physics methodology and highlight  how we applied it to establish the most rigorous constraints on four sterile neutrino models¹. 

The second part of the talk will discuss how I leveraged cosmological datasets to create a 3D map of interstellar dust temperature (see 3D map ). This allows for a more comprehensive study of the Milky Way's radiative properties, such as star formation regions and magnetic fields².

¹ Ref: Zelko et al. 2022 Phys. Rev. Lett. 129, 191301   

² Ref: Zelko et al. arxiv 2211.07667


Xiaolong Du (Carnegie)

Title: Soliton Merger Rates and Enhanced Axion Dark Matter Decay


Solitons are observed to form in simulations of dark matter (DM) halos consisting of bosonic fields. They are the ground states of the Schrödinger-Poisson equation with the self-gravity balanced by the so-called “quantum pressure”. The possible existence of solitons, being very dense and coherent lumps of DM, opens a wide range of possibilities concerning their phenomenology. For example, solitons composed of axion DM are unstable above a critical mass, and decay to either relativistic axions or photons, depending on the values of the coupling constants. The emitted photons can heat the intergalactic medium and alter the epoch of reionization. I will present our study on two mechanisms by which solitons lead to enhanced DM decay: by plasma blocking of parametric resonance, and by major mergers leading to formation of super-critical solitons. I will discuss how we can compute the enhanced DM decay rate using the extended Press-Schechter formalism and Monte Carlo merger trees. I will also show the new constraint on axion-photon coupling constants for axion mass in the range 1e-14 eV - 1e-8 eV we obtained using the Planck measurement on the Thompson optical depth.

Kevork Abazaijan