Deep Hubble Space Telescope Imaging on the Extended Ly$\alpha$ Emission
  of a QSO at $z = 2.19$ with Damped Lyman Alpha System as a Natural
  Coronagraph
  Recent observations suggest that proximate damped Ly$\alpha$ (PDLA) systems
can be used to study the host galaxies of Quasi-stellar objects (QSOs), because
the PDLAs can block the bright point-spread-function (PSF) from central QSOs.
Using six-orbits of narrowband imaging with $\it{HST}$/WFC3, we present the
first high resolution narrowband image of the Ly$\alpha$ emission in the PDLA
trough of the QSO SDSSJ115432.67-021537.9 . We detect one major component and
one minor component in the narrowband imaging. Combining the $\it{HST}$/WFC3
imaging with deep Magellan/MagE spectra, we measure that the Ly$\alpha$ flux
F$_{\rm{Ly\alpha}}$ = 1.56$\pm0.10 \times10^{-16}$ $\rm{erg\ s^{-1}\ cm^{-2}}$,
which is among the luminous ($\approx$ 2.7 L$^{\star}_{\rm{Ly\alpha}}$)
Ly$\alpha$ emitters at $\it{z} =$ 2.19. The $\rm{Ly\alpha}$-based star
formation rate (SFR) is $\sim$ 7 $\textrm{M_{\sun} \ yr^{-1}}$. These
observational results favor that the star formation from the host galaxy could
be the main mechanism to power the Ly$\alpha$ emission. This new method sheds
new light on the study of the kinematic structure and the spatial distribution
of the extended Ly$\alpha$ emitting regions around the QSO host.
