The (non)evolution of normal star forming galaxies since z=3

A fairly tight relation between the stellar mass and star formation rate
(SFR) of galaxies has been found to exist to z>3, that evolves with
redshift. This relation is often referred to as the "main sequence" of
star forming galaxies, as the tightness implies that galaxies spend most
of their evolution time on this (redshift dependent) relation. New
studies, largely driven by the new far-infrared surveys with Herschel,
find that galaxies on the main sequence at redshifts z<3 show very
similar properties to each other and likely form their stars in similar
local conditions, in a steady way over timescales of Gyrs. Major mergers
are outliers to the main sequence and seem to play only a minor role in
the overall stellar mass buildup. I will present some of these results
with emphasis on the PACS evolutionary probe (PEP) project.