Ly$\alpha$ and UV Sizes of Green Pea Galaxies
  Green Peas are nearby analogs of high-redshift Ly$\alpha$-emitting galaxies.
To probe their Ly$\alpha$ escape, we study the spatial profiles of Ly$\alpha$
and UV continuum emission of 24 Green Pea galaxies using the Cosmic Origins
Spectrograph (COS) on Hubble Space Telescope (HST). We extract the spatial
profiles of Ly$\alpha$ emission from their 2D COS spectra, and of UV continuum
from both the 2D spectra and NUV images. The Ly$\alpha$ emission shows more
extended spatial profiles than the UV continuum in most Green Peas. The
deconvolved Full Width Half Maximum (FWHM) of the Ly$\alpha$ spatial profile is
about 2 to 4 times that of the UV continuum in most cases. Since Green Peas are
analogs of high-z LAEs, it suggests that most high-z LAEs likely have larger
Ly$\alpha$ sizes than UV sizes. We also compare the spatial profiles of
Ly$\alpha$ photons at blueshifted and redshifted velocities in eight Green Peas
with sufficient data quality, and find the blue wing of the Ly$\alpha$ line has
a larger spatial extent than the red wing in four Green Peas with comparatively
weak blue Ly$\alpha$ line wings. We show that Green Peas and MUSE $z=3-6$ LAEs
have similar Ly$\alpha$ and UV continuum sizes, which probably suggests
starbursts in both low-z and high-z LAEs drive similar gas outflows illuminated
by Ly$\alpha$ light. Five Lyman continuum (LyC) leakers in this sample have
similar Ly$\alpha$ to UV continuum size ratios (~1.4-4.3) to the other Green
Peas, indicating their LyC emission escape through ionized holes in the
interstellar medium.
