Topical Seminar: Dwarf Spheroidal Galaxies: a window on to dark matter on the smallest scales

por Prof. Jorge Peñarrubia (University of Edinburgh, UK)

miércoles 26 mar. 2025 15:00 → 16:00 Europe/Madrid

1001-Primera-1-1-1 - Paterna. Seminario (Universe)

Being the most dark matter-dominated galaxies, dwarf spheroidal galaxies (dSphs) provide a crucial testing ground for a wide range of dark matter (DM) theories. A key prediction of Cold Dark Matter models is the existence of an enormous population of dark subhaloes, with masses potentially as small as planets (M~10^{-6} M_sol) or even asteroids (M ~ 10^{-12} M_sol). However, it remains an open question whether such tiny microhaloes can survive in a galactic tidal field and whether their presence leaves detectable imprints on the motions of stars.

In the first part of the talk, I will show that (i) cuspy subhaloes cannot be entirely disrupted by galactic tides and (ii) tidal disruption seen in simulations may be a numerical artifact caused by the limited resolution of N-body codes.

In the second, I will show how DM subhaloes with masses M>10^5 Msol can capture field stars in dSphs, forming temporarily bound "luminous" systems with unusual properties: (i) large sizes relative to their luminosity, (ii) stellar populations indistinguishable from those of their host galaxy, and (iii) extreme DM-dominated mass-to-light ratios, opening the possibility to test a wide range of DM models.

I will provide estimates of the number and properties of these objects in different galaxies and discuss several `anomalous' stellar systems detected in the Fornax and Eridanus II dSphs, which exhibit these characteristics.

 

Link to the recorded talk

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