A New Precision Measurement of the Small-Scale Line-of-Sight Power
  Spectrum of the Ly${\alpha}$ Forest
  We present a new measurement of the Ly${\alpha}$ forest power spectrum at
$1.8 < z < 3.4$ using 74 Keck/HIRES and VLT/UVES high-resolution, high-S/N
quasar spectra. We developed a custom pipeline to measure the power spectrum
and its uncertainty, which fully accounts for finite resolution and noise, and
corrects for the bias induced by masking missing data, DLAs, and metal
absorption lines. Our measurement results in unprecedented precision on the
small-scale modes $k > 0.02\,\mathrm{s\,km^{-1}}$, unaccessible to previous
SDSS/BOSS analyses. It is well known that these high-$k$ modes are highly
sensitive to the thermal state of the intergalactic medium, however
contamination by narrow metal lines is a significant concern. We quantify the
effect of metals on the small-scale power, and find a modest effect on modes
with $k < 0.1\,\mathrm{s\,km^{-1}} $. As a result, by masking metals and
restricting to $k < 0.1\,\mathrm{s\,km^{-1}}$ their impact is completely
mitigated. We present an end-to-end Bayesian forward modeling framework whereby
mock spectra with the same noise, resolution, and masking as our data are
generated from Ly${\alpha}$ forest simulations. These mocks are used to build a
custom emulator, enabling us to interpolate between a sparse grid of models and
perform MCMC fits. Our results agree well with BOSS on scales $k <
0.02\,\mathrm{s\,km^{-1}}$ where the measurements overlap. The combination of
BOSS' percent level low-$k$ precision with our $5-15\%$ high-$k$ measurements,
results in a powerful new dataset for precisely constraining the thermal
history of the intergalactic medium, cosmological parameters, and the nature of
dark matter. The power spectra and their covariance matrices are provided as
electronic tables.
