Testing Galaxy Formation at the Smallest Scales: The Discovery of a Starless RELHIC — Alejandro Benitez (University of Milano-Bicocca)

Within the standard LCDM model, galaxy formation theories predict a redshift-dependent «critical dark matter mass» threshold for galaxies to form, implying a large population of dark matter halos just below this mass should be starless. The most massive of these objects are free of complex stellar feedback and retain enough neutral hydrogen (HI) to be detectable in 21cm emission. They thus represent a unique and clean test of galaxy formation (and cosmological) models at the smallest scales. These systems are referred to as Reionization-Limited-HI Clouds (RELHICs). In this talk, I will discuss the theoretical framework for these curious systems and present a prime candidate for a starless halo. We have identified extended 21cm emission using the Five-hundred Aperture Radio Telescope (FAST), the Green Bank Observatory (GBT), and the Very Large Array (VLA). Crucially, follow-up observations with the Hubble Space Telescope (HST) have ruled out any luminous counterpart, making the most compelling detection of a RELHIC to date. I will conclude by discussing current uncertainties and the future theoretical and observational directions needed to strengthen this detection and uncover a larger population of these elusive objects.

Horarios: December 2, 2025 15:30

Publicado por: Gijs Mulders