So the pyramids are visible out to 3000 light years away if the aliens have extremely powerful optical telescopes. More recent developments, like satellites, might be visible out to 60ly. It is basically a signal travel speed issue.
So, the paper doesn't mention this, but if -- and only if -- they're looking for pyramids, we're visible to about 0.1% of the galaxy.
So, the paper doesn't mention this, but if -- and only if -- they're looking for pyramids, we're visible to about 0.1% of the galaxy.