Abstract
Unveiling massive galaxies at high redshift in the JWST era.
Adriano Fontana (INAF OAR)
Andrea Grazian, Emiliano Merlin, Marco Castellano
Despite the recent results from CANDELS and other deep near IR surveys, the census and nature of massive galaxies at redhifts larger than 3 is still uncertain. While the population of star-forming, moderately extincted galaxies is well represented in the LBG population, there are clear indications that even at z=4-5 massive and red galaxies do exist (e.g. Grazian+14, Straatman+14) although they become rarer, following the overall decline of the dusty or quiescent populations. Clearly their existence shows that the evolutionary path of galaxies at high redshift is more complicated than what the simple LBG population tells us - and that powerful physical mechanism must be in place at high redshift to form (and in some case make quiescent) these objects. Despite their relatively small number density, these objects may substancially contribute to the star-formation rate and stellar mass density. I will first summarize the most recent results, partly yet unpublished, on the evolution of the mass function and the statistics of massive galaxies at z>3, focusing in particular on the passive population. These results use the best of recent HST and ground-based surveys (CANDELS, UltraVista, Frontier Fields) nevertheless they do not allow us to assess the nature of these galaxies. I will show that given the inadequate depth of the HST data, we cannot determine with reliability the redshift distribution and evolution of these objects, distinguish between star-forming, dusty and passive galaxies, etc. And we are unable to determine whether these objects exist also among the faintest galaxies - a regime that is beyond reach of current instrumentation. To overcome these limitations, we need to push our imaging and spectroscopic capabilities in the near—IR regime (3-10mu), i.e., exactly into the realm of JWST. I will quantitatively show the improvements that moderately deep fields with JWST can yield in uncovering this elusive yet fundamental population.
Talk