How much do the Avengers know of Thanos?

Question

Given Thor's dialogue at the end of Age of Ultron, obviously the Avengers don't know about Thanos per se. However, he knows someone is out there. For example, Thor would know that the Chitauri weren't an Asgardian force, that Loki got them from someone. We know it to be Thanos, and from the comics, we know a great deal about him. However, the full depth of this is hidden from the Avengers.

How much do the Avengers know about the person behind the attack on New York (i.e. Thanos), and the gathering of the Infinity Stones?

Answer 1

To the best of the knowledge that can be garnered purely from on-screen footage, nothing.

The only people who could have such knowledge are Thor (being somewhat knowledgeable about the realms and their inhabitants), the Guardians of the Galaxy (who know all about him, but have no inclination towards visiting Terra that we're aware of), Loki (who served'ish' him), and Heimdall (he sees all).

It's certainly possible that someone (such as Hawkeye or Dr. Selvig) who Loki was mind-controlling would know something, but I didn't really get that feeling - if it was something they were consciously aware of, they'd probably have mentioned it. Otherwise, I doubt Loki was in the habit of sitting his suborned agents down and explaining the hierarchy (above himself, at least).

Thus, I'm guessing that the main feature the Guardians of the Galaxy will add to the 'main' Marvel Cinematic Universe (other than Tony/Rocket interactions, which would likely deserve a movie all on their own) is getting the info on Thanos to the Avengers.