Iterating through custom map && handling several streams

I'm new to C++ and not 100% sure how I can iterate over maps.
For the project, I need to have a map that stores key: [name of file / stream] and value: [logger::severity]. Among the filenames there might be an object of ostream cout.

I came up to pretty much nothing:

enum class severity
    {
        trace,
        debug,
        information,
        warning,
        error,
        critical
    };

std::map<std::ofstream, severity> this_loggers_streams;

for (std::map<std::ofstream, severity>::iterator iter = this_loggers_streams.begin(); 
          iter != this_loggers_streams.end(); ++iter) {
      iter->first << "" << std::endl;      
      }
}

My IDE warns me that there is a no viable conversion for my iterator and Invalid operands to binary expression (const std::basic_ofstream<char> and const char[1]).

How can I iterate over my map? What will be the best solution to have an ability to write in file and in std::cout as it can be a member of my map?

Keys in a map are const values. That code is invalid and can't be fixed without changing the software design:

iter->first << "" << std::endl;  // iter->first is const std::ofstream

A possible change:

std::list<std::pair<std::ofstream, severity>> this_loggers_streams;