Affiliation: Carnegie Observatories

Contribution: Oral

Title: Cosmic history and cosmic-ray physics with deep radio observations

Abstract: The ubiquitous processes governing galaxy growth and evolution such as star formation and subsequent supernovae produce very weak radio sources. Modern radio interferometers are now sensitive enough to probe the most fundamental metric of when and how quickly galaxies built up their stellar mass: the evolution of the star formation rate density (SFRD). The peak in the cosmic SFRD at z~2 also marks the peak of dust attenuation, making the full census of star formation activity at UV-IR wavelengths a measurement fraught with uncertainty. Fortunately, radio emission from normal galaxies free-free emission of massive stars, and synchrotron emission of relativistic electrons shocked in the supernovae remnants of the same short-lived massive stars emitting primarily in the UV and optical is entirely unaffected by dust. Five years ago, MeerKAT produced the deepest radio image to date (MeerKAT-DEEP2), and with it we measured a radio-based cosmic SFRD both indirectly through the evolutionary models needed to match radio source counts and directly from the luminosities of individual galaxies that is at least twice that inferred through UV-IR measurements, even at redshifts as low as z~0.5. In this talk, I will outline ongoing and future plans to reveal the source(s) of this discrepancy, and demonstrate how deep radio observations are poised to illuminate the physics of cosmic ray transport and its role in galaxy evolution.

This contribution can be found here (pdf).