  We demonstrate a high-flux and low transverse temperature atomic beam of
ytterbium by applying two-dimensional cooling using the
${}^1\mathrm{S}_0\text{-}{}^3\mathrm{P}_1$ intercombination transition to the
cold atomic beam produced by the dipolar-allowed
${}^1\mathrm{S}_0\text{-}{}^1\mathrm{P}_1$ transition. The optimized transverse
temperature of $11 \pm 9\,\mathrm{\mu K}$ and an atomic flux of $(7.5 \pm 1.0)
\times 10^8\,\mathrm{atoms/s}$ are obtained for the atomic beam whose
longitudinal velocity is $30\,\mathrm{m/s}$. The transverse temperature is
maintained below $23\,\mathrm{\mu K}$, while the flux is above $6.5 \times
10^8\,\mathrm{atoms/s}$ in the longitudinal velocity range of $22 -
30\,\mathrm{m/s}$. We also discuss the feasibility of further narrowing the
transverse momentum width to less than the recoil momentum using the
momentum-selective optical transition between the ground state and the
long-lived metastable state. The transverse momentum width of our atomic beam,
which is narrower than 5.7 times the recoil momentum, is a good starting point
for the proposed method.
