  We conducted an in-depth analysis of candidate member stars located in the
peripheries of three ultra-faint dwarf (UFD) galaxy satellites of the Milky
Way: Bo\"otes I (Boo1), Bo\"otes II (Boo2), and Segue I (Seg1). Studying these
peripheral stars has previously been difficult due to contamination from the
Milky Way foreground. We used $u$-band photometry from the Dark Energy Camera
(DECam) to derive metallicities to efficiently select UFD candidate member
stars. This approach was validated on Boo1, where we identified both previously
known and new candidate member stars beyond five half-light radii. We then
applied a similar procedure to Boo2 and Seg1. Our findings hinted at evidence
for tidal features in Boo1 and Seg1, with Boo1 having an elongation consistent
with its proper motion and Seg1 showing some distant candidate stars, a few of
which are along its elongation and proper motion. We find two Boo2 stars at
large distances consistent with being candidate member stars. Using a
foreground contamination rate derived from the \emph{Besan\c{c}on} Galaxy
model, we ascribed purity estimates to each candidate member star. We recommend
further spectroscopic studies on the newly identified high-purity members. Our
technique offers promise for future endeavors to detect candidate member stars
at large radii in other systems, leveraging metallicity-sensitive filters with
the Legacy Survey of Space and Time and the new, narrow-band Ca HK filter on
DECam.
