We present U _ { 336 } V _ { 606 } J _ { 125 } H _ { 160 } follow-up HST observations of 16 z \sim 3 candidate LyC emitters in the HS1549+1919 field .
With these data , we obtain high spatial-resolution photometric redshifts of all sub-arcsecond components of the LyC candidates in order to eliminate foreground contamination and identify robust candidates for leaking LyC emission .
Of the 16 candidates , we find one object with a robust LyC detection that is not due to foreground contamination .
This object ( MD5 ) resolves into two components ; we refer to the LyC-emitting component as MD5b .
MD5b has an observed 1500Å to 900Å flux-density ratio of ( F _ { UV } / F _ { LyC } ) _ { obs } = 4.0 \pm 2.0 , compatible with predictions from stellar population synthesis models .
Assuming minimal IGM absorption , this ratio corresponds to a relative ( absolute ) escape fraction of f _ { esc,rel } ^ { MD 5 b } = 75 - 100 % ( f _ { esc,abs } ^ { MD 5 b } = 14 - 19 % ) .
The stellar population fit to MD5b indicates an age of \lesssim 50 Myr , which is in the youngest 10 % of the HST sample and the youngest third of typical z \sim 3 Lyman break galaxies , and may be a contributing factor to its LyC detection .
We obtain a revised , contamination-free estimate for the comoving specific ionizing emissivity at z = 2.85 , indicating ( with large uncertainties ) that star-forming galaxies provide roughly the same contribution as QSOs to the ionizing background at this redshift .
Our results show that foreground contamination prevents ground-based LyC studies from obtaining a full understanding of LyC emission from z \sim 3 star-forming galaxies .
Future progress in direct LyC searches is contingent upon the elimination of foreground contaminants through high spatial-resolution observations , and upon acquisition of sufficiently deep LyC imaging to probe ionizing radiation in high-redshift galaxies .