The Far Infrared Emission of the First Massive Galaxies
  Massive Population II galaxies undergoing the first phase of vigorous star
formation after the initial Population III stage should have high energy
densities and silicate-rich interstellar dust. We have modeled the resulting
far-infrared spectral energy distributions (SEDs), demonstrating that they are
shifted substantially to bluer (`warmer') wavelengths relative to the best
fitting ones at z ~ 3, and with strong outputs in the 10 - 40 micron range.
When combined with a low level of emission by carbon dust, their SEDs match
that of Haro 11, a local moderately-low-metallicity galaxy undergoing a very
young and vigorous starburst that is likely to approximate the relevant
conditions in young Population II galaxies. We expect to see similar SEDs at
high redshifts (z >= 5) given the youth of galaxies at this epoch. In fact, we
find a progression with redshift in observed galaxy SEDs, from those resembling
local ones at 2 < z < 4 to a closer resemblance with Haro 11 at 5 < z < 7. In
addition to the insight on conditions in high redshift galaxies, this result
implies that estimates of the total infrared luminosities at z ~ 6 based on
measurements near lambda ~ 1 mm can vary by factors of 2 - 4, depending on the
SED template used. Currently popular modified blackbodies or local templates
can result in significant underestimates compared with the preferred template
based on the SED of Haro 11.
