Speaker
Description
We present evidence for deviations from the collisionless Cold Dark Matter (CDM) paradigm. In the standard model, dark matter (DM) is collisionless and forms halos with dense central cusps, known as NFW profiles. However, observed galaxies often exhibit flat central cores, typical of systems in thermodynamic equilibrium. While baryonic processes can transform cusps into cores in more massive galaxies, these mechanisms fail in low-stellar-mass systems (<1e6 Msun). Therefore, detecting cores in such galaxies suggests that DM may not be entirely collisionless, hinting at its true, unknown nature—possibly fuzzy, self-interacting (SIDM), or warm DM. Traditional dynamical methods can't probe DM in tiny galaxies, so we developed a new technique using stellar photometry alone. Applying it to six Ultra Faint Dwarf galaxies (1e3–1e4 Msun), we found they reside in cored rather than cuspy halos. After excluding other explanations, our results strongly support alternative DM models that go beyond standard CDM assumption.
