A Survey for New Members of Taurus from Stellar to Planetary Masses
  We present a large sample of new members of the Taurus star-forming region
that extend from stellar to planetary masses. To identify candidate members at
substellar masses, we have used color-magnitude diagrams and proper motions
measured with several wide-field optical and infrared (IR) surveys. At stellar
masses, we have considered the candidate members that were found in a recent
analysis of high-precision astrometry from the Gaia mission. Using new and
archival spectra, we have measured spectral types and assessed membership for
these 161 candidates, 79 of which are classified as new members. Our updated
census of Taurus now contains 519 known members. According to Gaia data, this
census should be nearly complete for spectral types earlier than M6-M7 at
A_J<1. For a large field encompassing ~72% of the known members, the census
should be complete for K<15.7 at A_J<1.5, which corresponds to ~5-13 M_Jup for
ages of 1-10 Myr based on theoretical evolutionary models. Our survey has
doubled the number of known members at greater or equal to M9 and has uncovered
the faintest known member in M_K, which should have a mass of ~3-10 M_Jup for
ages of 1-10 Myr. We have used mid-IR photometry from the Spitzer Space
Telescope and the Wide-field Infrared Survey Explorer to determine whether the
new members exhibit excess emission that would indicate the presence of
circumstellar disks. The updated disk fraction for Taurus is ~0.7 at less than
or equal to M3.5 and ~0.4 at >M3.5.
