Gas Giants in Hot Water: Inhibiting Giant Planet Formation and Planet
  Habitability in Dense Star Clusters Through Cosmic Time
  I show that the temperature of nuclear star clusters, starburst clusters in
M82, compact high-z galaxies, and some globular clusters of the Galaxy likely
exceeded the ice line temperature (T_Ice ~ 150-170 K) during formation for a
time comparable to the planet formation timescale. The protoplanetary disks
within these systems will thus not have an ice line, decreasing the total
material available for building protoplanetary embryos, inhibiting the
formation of gas- and ice-giants if they form by core accretion, and
prohibiting habitability. Planet formation by gravitational instability is
similarly suppressed because Toomre's Q > 1 in all but the most massive disks.
I discuss these results in the context of the observed lack of planets in 47
Tuc. I predict that a similar search for planets in the globular cluster NGC
6366 ([Fe/H] = -0.82) should yield detections, whereas (counterintuitively) the
relatively metal-rich globular clusters NGC 6440, 6441, and 6388 should be
devoid of giant planets. The characteristic stellar surface density above which
T_Ice is exceeded in star clusters is ~6 x 10^3 M_sun/pc^2 f_{dg, MW}^{-1/2},
where f_{dg, MW} is the dust-to-gas ratio of the embedding material, normalized
to the Milky Way value. Simple estimates suggest that ~5 - 50% of the stars in
the universe formed in an environment exceeding this surface density. Caveats
and uncertainties are detailed.
