How are image credits expressed in Astronomy presentations?
There is no conventional format, really. For publications purposes if one uses data from a telescope or image or code created by someone else or similar, the source usually requests being cited or acknowledged in a form specific to their own taste. Some examples include what you quoted or “This paper makes use of the following ALMA data: ADS/JAO.ALMA#******. ALMA is a partnership of ... “.
Answering your question.

For ESA and NASA there is probably a difference between “/“ and “&amp;”.
For a publication in a journal you must follow the exact wording.
If you just give a presentation no one minds if you use your favorite formatting while acknowledging all parties involved.