Dissolved Massive Metal-Rich Globular Clusters Can Cause the Range of UV
  Upturn Strengths Found among Early-type Galaxies
  I discuss a scenario in which the ultraviolet (UV) upturn of giant early-type
galaxies (ETGs) is primarily due to helium-rich stellar populations that formed
in massive metal-rich globular clusters (GCs) which subsequently dissolved in
the strong tidal field in the central regions of the massive host galaxy. These
massive GCs are assumed to show UV upturns similar to those observed recently
in M87, the central giant elliptical galaxy in the Virgo cluster of galaxies.
Data taken from the literature reveals a strong correlation between the
strength of the UV upturn and the specific frequency of metal-rich GCs in ETGs.
Adopting a Schechter function parametrization of GC mass functions, simulations
of long-term dynamical evolution of GC systems show that the observed
correlation between UV upturn strength and GC specific frequency can be
explained by variations in the characteristic truncation mass ${\cal{M}}_{\rm
c}$ such that ${\cal{M}}_{\rm c}$ increases with ETG luminosity in a way that
is consistent with observed GC luminosity functions in ETGs. These findings
suggest that the nature of the UV upturn in ETGs and the variation of its
strength among ETGs are causally related to that of helium-rich populations in
massive GCs, rather than intrinsic properties of field stars in massive
galactic spheroids. With this in mind, I predict that future studies will find
that [N/Fe] decreases with increasing galactocentric radius in massive ETGs,
and that such gradients have the largest amplitudes in ETGs with the strongest
UV upturns.
