Unable to delete indexes on splunk cloud

[Afak]

I have created some indexes on splunk cloud can we not delete this indexes ? Because the option for delete is disabled in splunk cloud , can anyone help with this ? 

[Afak]

I have created indexes on web interface of splunk cloud and it was not specific to any app and since i have created those indexes i think we can rule out the possibility of them being system-defined.

[richgalloway]

It's common for knowledge objects in Splunk Cloud to be undeletable if they are defined in the default directory of an app.  In that case, you must edit the app and re-upload it.

Some indexes cannot be deleted because they are system-defined.