Chronos: A NIR spectroscopic galaxy survey. From the formation of
  galaxies to the peak of activity
  Chronos is our response to ESA's call for white papers to define the science
for the future L2, L3 missions. Chronos targets the formation and evolution of
galaxies, by collecting the deepest NIR spectroscopic data, from the formation
of the first galaxies at z~10 to the peak of formation activity at z~1-3. The
strong emission from the atmospheric background makes this type of survey
impossible from a ground-based observatory. The spectra of galaxies represent
the equivalent of a DNA fingerprint, containing information about the past
history of star formation and chemical enrichment. The proposed survey will
allow us to dissect the formation process of galaxies including the timescales
of quenching triggered by star formation or AGN activity, the effect of
environment, the role of infall/outflow processes, or the connection between
the galaxies and their underlying dark matter haloes. To provide these data,
the mission requires a 2.5m space telescope optimised for a campaign of very
deep NIR spectroscopy. A combination of a high multiplex and very long
integration times will result in the deepest, largest, high-quality
spectroscopic dataset of galaxies from z=1 to 12, spanning the history of the
Universe, from 400 million to 6 billion years after the big bang, i.e. covering
the most active half of cosmic history.
