After Death
Posthumously
noun
All the art, music, or books that come out after a person dies are considered to be released after death or posthumously.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
没後50年を記念した展覧会を予定しています。
A commemoration exhibition is planned 50 years after their death.