A Census of the Circumstellar Disk Populations in the Sco-Cen Complex
  I have used mid-infrared (IR) photometry from the Wide-field Infrared Survey
Explorer (WISE) to perform a census of circumstellar disks among ~10,000
candidate members of the Sco-Cen complex that were recently identified with
data from the Gaia mission. IR excesses are detected for more than 1200 of the
WISE counterparts that are within the commonly adopted boundary for Sco-Cen,
~400 of which are newly reported in this work. The richest population in
Sco-Cen, UCL/LCC, contains the largest available sample of disks (>500) for any
population near its age (~20 Myr). UCL/LCC also provides the tightest
statistical constraints to date on the disk fractions of low-mass stars for any
single age beyond that of Upper Sco (~11 Myr). For Upper Sco and UCL/LCC, I
have measured the disk fractions as a function of spectral type. The disk
fraction in Upper Sco is higher at later spectral types, which is consistent
with the results for previous samples of candidate members. In UCL/LCC, that
trend has become more pronounced; the disk fractions in UCL/LCC are lower than
those in Upper Sco by factors of ~10, 5.7, and 2.5 at B7-K5.5, K6-M3.5, and
M3.75-M6, respectively. The data in UCL/LCC also demonstrate that the disk
fraction for low-mass stars remains non-negligible at an age of 20 Myr
(0.09+/-0.01). Finally, I find no significant differences in the ages of
disk-bearing and diskless low-mass stars in Upper Sco and UCL/LCC based on
their positions in color-magnitude diagrams.
