*Jim Condon (NRAO)*
Allison Matthews(University of Virginia)
Eric Murphy(NRAO)
Topic: Galaxy Evolution
*Tracing the Star Formation History of the Universe via Free-free
Emission***
Ultraviolet (UV) and far-infrared (FIR) data indicate that the comoving
star-formation rate density peaked at cosmic noon (/z/ ∼2) and that >
95% of all stellar mass assembly has occurred since /z/ ∼ 4. However,
most UV emission is absorbed in dusty star-forming galaxies (SFGs). Cold
dust illuminated by older stars contaminates the FIR emission of
low-luminosity SFGs, and existing FIR images can detect only the most
luminous galaxies beyond cosmic noon. The radio continuum luminosities
of SFGs are proportional to their recent star-formation rates, unbiased
by dust or older stars. The confusion-limited 1.3 GHz MeerKAT DEEP2
image is sensitive enough to trace the evolution of most SFGs via their
synchrotron emission, but inverse-Compton scattering off the cosmic
microwave background may suppress synchrotron radiation at high
redshifts. Only an ngVLA Band 3 (16 GHz) confusion-limited image with
resolution will be able to detect the 60 nJy free-free emission tracing
the star formation history of all galaxies that produced > 85% of the
stellar mass in the universe today.
