Mechanisms regulating the escape of Ly \alpha photons and ionizing radiation remain poorly understood .
To study these processes we analyze VLA 21cm observations of one Green Pea ( GP ) , J160810+352809 ( hereafter J1608 ) , and HST COS spectra of 17 GP galaxies at z < 0.2 .
All are highly ionized : J1608 has the highest [ O III ] \lambda 5007 / [ O II ] \lambda 3727 for star-forming galaxies in SDSS , and the 17 GPs have [ O III ] / [ O II ] \geq 6.6 .
We set an upper limit on J1608 ’ s HI mass of \log M _ { HI } / M _ { \odot } = 8.4 , near or below average compared to similar mass dwarf galaxies .
In the COS sample , eight GPs show Ly \alpha absorption components , six of which also have Ly \alpha emission .
The HI column densities derived from Ly \alpha absorption are high , \log N _ { HI } / cm ^ { -2 } = 19 - 21 , well above the LyC optically thick limit .
Using low-ionization absorption lines , we measure covering fractions ( f _ { \mbox { \scriptsize cov } } ) of 0.1 - 1 , and find that f _ { \mbox { \scriptsize cov } } strongly anti-correlates with Ly \alpha escape fraction .
Low covering fractions may facilitate Ly \alpha and LyC escape through dense neutral regions .
GPs with f _ { \mbox { \scriptsize cov } } \sim 1 all have low neutral gas velocities , while GPs with lower f _ { \mbox { \scriptsize cov } } = 0.2 - 0.6 have a larger range of velocities .
Conventional mechanical feedback may help establish low f _ { \mbox { \scriptsize cov } } in some cases , whereas other processes may be important for GPs with low velocities .
Finally , we compare f _ { \mbox { \scriptsize cov } } with proposed indicators of LyC escape .
Ionizing photon escape likely depends on a combination of neutral gas geometry and kinematics , complicating the use of emission-line diagnostics for identifying LyC emitters .