Wednesday Colloquium


"Research at AstroCeNT in the context of the Global Argon Dark Matter program"

Marcin Kuźniak (CAMK, AstroCeNT, Warsaw)

The search for interactions of dark matter particles (WIMPs) with ordinary matter is carried out with large detectors, with currently the most promising detection technology based on the use of a large mass of liquid argon or xenon as the detector medium. Efficient collection and detection of light from multi-tonne detectors poses challenges and motivates dedicated R&D on optical materials, including wavelength shifters, as well as on photosensors. Such work at AstroCeNT, either in the context of the Global Argon Dark Matter Collaboration, or general R&D applicable also to neutrino detectors, will be presented, together with an overview of the field.


"Internal kinematics of the Milky Way dSph satellites: observations and simulations"

Alberto Martinez-Garcia (Instituto de Astrofísica de Canarias)

Dwarf spheroidal galaxies (dSph) are the most numerous satellites of the Milky Way (MW). Due to their proximity, their stellar population can be resolved, allowing us to study them in depth. However, the internal kinematics of dSphs remains one of their least known aspects. We present a kinematic study of six of the dSph satellites of the MW. We combine proper motions from the Gaia DR3 and line-of-sight velocities from previous works to derive their 3D internal kinematics. We detect coherent motions in a number of these systems. We find, for the first time, rotation in the plane of the sky in three of the classical satellites of the MW, namely Carina, Fornax and Sculptor. We also detect velocity gradients in Draco, Ursa Minor, Carina, and Fornax. The amplitude of the gradients appears to be related to the orbital history of the dSphs, suggesting that the interaction with the MW is causing them. We also explore the internal kinematics of dwarf satellites of the TNG50 simulation to asses our observational findings in the MW and the role that the interaction with the host plays in the evolution of the internal kinematics.


"The Important Role of Cosmic Ray Transport in Galaxy Evolution"

Philipp Kempski (Princeton University)

Although negligible by number density, relativistic cosmic rays (CRs) are an energetically important component of the plasmas filling galaxies and galaxy clusters. As a result, these particles may play an important role in shaping large-scale galactic (thermo)dynamics, for example by driving galactic winds and/or heating diffuse gas in galaxy halos. For this reason, “CR feedback” has become a key ingredient in galaxy evolution models. However, a fundamental limitation of these models is that the nature of CR feedback is a very strong function of the assumed CR transport, which remains uncertain. In this talk, I will give an overview of CR feedback in galaxies, discuss theoretical uncertainties in CR propagation and how CR spectra measured at Earth help us constrain the physics of their transport. I will argue that popular existing transport models are full of theoretical uncertainties and are generally not in good agreement with observations. This suggests that we may need a new theory of CR transport.


"Overview of Dark Matter Production in Nonstandard Cosmologies with a Focus on Axions"

Jacek Ksawery Osinski (AstroCent/CAMK, Warsaw)

The Universe is typically assumed to be radiation dominated in the period preceding big bang nucleosynthesis, however we do not currently have any observational probes to confirm this. Nonstandard cosmological histories, where some other form of energy density dominates for a time, commonly arise in theories of the early Universe. These histories have important consequences for processes, such as dark matter production, occurring in that time. In this talk I will briefly review nonstandard cosmological histories and their effects on dark matter production focusing on axion dark matter.