Epoch of Reionization Power Spectrum Limits from Murchison Widefield
  Array Data Targeted at EoR1 Field
  Current attempts to measure the 21cm Power Spectrum of neutral hydrogen
during the Epoch of Reionization are limited by systematics which produce
measured upper limits above both the thermal noise and the expected
cosmological signal. These systematics arise from a combination of
observational, instrumental, and analysis effects. In order to further
understand and mitigate these effects, it is instructive to explore different
aspects of existing datasets. One such aspect is the choice of observing field.
To date, MWA EoR observations have largely focused on the EoR0 field. In this
work, we present a new detailed analysis of the EoR1 field. The EoR1 field is
one of the coldest regions of the Southern radio sky, but contains the very
bright radio galaxy Fornax-A. The presence of this bright extended source in
the primary beam of the interferometer makes the calibration and analysis of
EoR1 particularly challenging. We demonstrate the effectiveness of a recently
developed shapelet model of Fornax-A in improving the results from this field.
We also describe and apply a series of data quality metrics which identify and
remove systematically contaminated data. With substantially improved source
models, upgraded analysis algorithms and enhanced data quality metrics, we
determine EoR power spectrum upper limits based on analysis of the best
$\sim$14-hours data observed during 2015 and 2014 at redshifts 6.5, 6.8 and
7.1, with the lowest $2\sigma$ upper limit at z=6.5 of $\Delta^2 \leq (73.78
~\mathrm{mK)^2}$ at $k=0.13~\mathrm{h~ Mpc^{-1}}$, improving on previous EoR1
measurement results.
