def merged_gasmap(self, **kwargs):
        """ return the file name for Galprop merged gasmaps
        """
        kwargs_copy = self.base_dict.copy()
        kwargs_copy.update(**kwargs)
        self._replace_none(kwargs_copy)        
        localpath = NameFactory.merged_gasmap_format.format(**kwargs_copy)
        if kwargs.get('fullpath', False):
            return self.fullpath(localpath=localpath)
        return localpath