Joint Astrophysics Colloquium

A near-infrared excess in the continuum of high-redshift galaxies: a tracer of star formation, circumstellar disks, and (maybe) extra-galactic planets?

Bob Abraham

University of Toronto

I describe recent observations of a puzzling near-infrared excess in the continuum of high-redshift galaxies. This excess is correlated with star formation rate, so practical-minded observational cosmologists seeking to measure the cosmic star-formation rate at high-redshifts may find the excess to be a useful tool. Less practical-minded people may find the excess interesting for a different reason. I will argue that the IR excess is probably coming from young circumstellar disks formed around high-mass stars in the distant galaxies we are observing. Assuming circumstellar disks extend down to lower masses, as they do in our own Galaxy, the excess emission presents us with an exciting opportunity to measure the formation rate of planetary systems in distant galaxies at cosmic epochs before our own Solar System formed.