Talks

The impact of feedback from galaxy formation on cosmological probes is typically quantified in terms of the suppression of the matter power spectrum in hydrodynamical compared to gravity-only simulations. In this paper, we instead study how baryonic feedback impacts halo assembly histories and thereby imprints on cosmological observables. We investigate the sensitivity of the thermal Sunyaev-Zel'dovich effect (tSZ) power spectrum, X-ray number counts, weak lensing and kinetic Sunyaev-Zel'dovich (kSZ) stacked profiles to halo populations as a function of mass and redshift. We then study the imprint of different feedback implementations in the FLAMINGO suite of cosmological simulations on the assembly histories of these halo populations, as a function of radial scale. We find that kSZ profiles target lower-mass halos (M200m∼10^13.1M⊙) compared to all other probes considered (M200m∼10^15M⊙). Feedback is inefficient in high-mass clusters with ∼10^15M⊙ at z=0, but was more efficient at earlier times in the same population, with a ∼5-10% effect on mass at 22). These findings are tied together by noting that, regardless of redshift, feedback most efficiently redistributes baryons when halos reach a mass of M200m≃10^12.8M⊙ and ceases to have any significant effect by the time M200m≃10^15M⊙. We put forward strategies for minimizing sensitivity of lensing analyses to baryonic feedback, and for exploring baryonic resolutions to the unexpectedly low tSZ power in cosmic microwave background observations.

Observational surveys of the distribution of matter in the universe are becoming ever more precise and continue to be extended to smaller scales. This necessitates accounting for the fact that baryons do not precisely trace the dark matter. The redistribution of baryons by galactic winds, which is the major bottleneck in our understanding of galaxy evolution, therefore requires a convergence between models of large-scale structure and cosmology. I will discuss some of the insights gained from cosmological, hydrodynamical simulations, and challenges that need to be overcome to make further progress. I will present recent results from the FLAMINGO suite of large-volume cosmological, hydrodynamical simulations, which provide insight into the importance of baryonic effects for cosmology using large-scale structure and galaxy clusters. Finally, I will present the COLIBRE simulations of galaxy formation, a new suite of cosmological hydrodynamical simulations that removes important shortcomings of previous simulations.

Terrestrial ecosystems exhibit ecological stability: If an ecosystem is perturbed, biological feedback drives it back toward an equilibrium state, but an ecosystem does not remain stuck in its equilibrium state because it is continually perturbed. Are galaxies really similar to biological ecosystems in that regard? My talk will consider whether the atmospheres of galaxies have feedback-regulated equilibrium states and what the observational consequences of those states might be. While considering those questions I will lay out a framework for classifying how halo-scale feedback loops operate.