  We extract the galaxy density and momentum power spectra from a subset of
early-type galaxies in the SDSS DR7 main galaxy catalog. Using galaxy distance
information inferred from the improved fundamental plane described in
\citet{Yoon_2020}, we reconstruct the peculiar velocities of the galaxies and
generate number density and density-weighted velocity fields, from which we
extract the galaxy density and momentum power spectra. We compare the measured
values to the theoretical expectation of the same statistics, assuming an input
$\Lambda$CDM model and using a third-order perturbative expansion. After
validating our analysis pipeline with a series of mock data sets, we apply our
methodology to the SDSS data and arrive at constraints $f\sigma_{8} =
0.471_{-0.080}^{+0.077}$ and $b_{1}\sigma_{8} = 0.920_{-0.070}^{+0.070}$ at a
mean redshift $\bar{z} = 0.04$. Our result is consistent with the Planck
cosmological best fit parameters for the $\Lambda$CDM model. The momentum power
spectrum is found to be strongly contaminated by small scale velocity
dispersion, which suppresses power by $\sim {\cal O}(30\%)$ on intermediate
scales $k \sim 0.05 \, h \, {\rm Mpc}^{-1}$.
