Targeting Bright Metal-poor Stars in the Disk and Halo Systems of the
  Galaxy
  We present the results of spectroscopic follow-up for 1897 low-metallicity
star candidates, selected from the Best & Brightest (B&B) Survey, carried out
with the GMOS-N/S (Gemini North/South telescopes) and Goodman (SOAR Telescope)
spectrographs. From these low-resolution ($R \sim 2000$) spectra, we estimate
stellar atmospheric parameters, as well as carbon and magnesium (representative
of $\alpha$ elements) abundance ratios. We confirm that $56\%$ of our program
stars are metal-poor ([Fe/H] $< -1.0$), $30\%$ are very metal-poor (VMP; [Fe/H]
$< -2.0$) and $2\%$ are extremely metal-poor (EMP; [Fe/H] $< -3.0$). There are
191 carbon-enhanced metal-poor (CEMP) stars, resulting in CEMP fractions of
$19\%$ and $43\%$ for the VMP and EMP regimes, respectively. A total of 94
confirmed CEMP stars belong to Group I ($A({\rm C}) \gtrsim 7.25$) and 97 to
Group II ($A({\rm C}) \lesssim 7.25$) in the Yoon-Beers $A$(C)$-$[Fe/H]
diagram. Moreover, we combine these data with Gaia EDR3 astrometric information
to delineate new target-selection criteria, which have been applied to the
Goodman/SOAR candidates, to more than double the efficiency for identification
of bona-fide VMP and EMP stars in comparison to random draws from the B&B
catalog. We demonstrate that this target-selection approach can achieve success
rates of $96\%$, $76\%$, $28\%$ and $4\%$ for [Fe/H] $\leq -1.5$, $\leq -2.0$,
$\leq -2.5$ and $\leq -3.0$, respectively. Finally, we investigate the presence
of dynamically interesting stars in our sample. We find that several VMP/EMP
([Fe/H] $\leq -2.5$) stars can be associated with either the disk system or
halo substructures like Gaia-Sausage/Enceladus and Sequoia.
