This command lists all branches and their author names
git for-each-ref --format=" %(authorname) %09 %(refname)" --sort=authorname
If you are using github you can also visit https://github.com/author/repo/branches/yours to get all your branches
If you want to just delete all the already merged branches you can us the command
git branch --merged | grep -v "\*" | grep -v master | grep -v dev | xargs -n 1 git branch -d
For more details of git for-each-ref visit here.