The first gigayear of bulge star formation in Virgo ellipticals:
  constraints from their globular cluster systems
  Data products from the Advanced Camera for Surveys Virgo Cluster Survey are
used to understand the bulge star formation history in early-type galaxies at
redshifts z > 2. A new technique is developed whereby observed high-redshift
age-metallicity relationships are utilized to constrain the typical formation
epochs of metal-rich or "bulge" globular clusters. This analysis supports a
model where massive Virgo galaxies underwent an extremely intense mode of bulge
globular cluster formation at z ~ 3.5 that was followed by an era of
significant bulge growth and little globular cluster production.
Intermediate-mass galaxies showed a less-intense period of globular cluster
formation at z ~ 2.5 that was synchronized with the bulk of bulge star growth.
The transition between the massive and intermediate-mass galaxy star formation
modes occurs at a galaxy stellar mass of M_stellar ~ 3 x 10^10 M_sun, the mass
where many other galaxy properties are observed to change. Dwarf early-type
galaxies in Virgo may have experienced no significant period of bulge globular
cluster formation, thus the intense star bursts associated with globular
cluster formation may be difficult to directly observe at redshifts z < 4.
Though the above conclusions are preliminary because they are based upon
uncertain relationships between age and metallicity, the technique employed
will yield more stringent constraints as high-redshift galaxy observations and
theoretical models improve.
