Well a rogue galactic core ejected and spinning around the intergalactic void would be very hard to spot it would be a different story if it entered a galaxy. Out in the intergalactic void there's way more space and way less things for it to perturb so you could see it, inside a a star dense region though it would be perturb stuff like a Rhino charging through a grove of saplings. You'd have to be looking to see it to be sure but they're going to be bending orbits in a rather noteworthy fashion, to give a somewhat oversimplified example, something in the million SM region would be exerting a force on objects similar to what the sun exerts on Jupiter out at about a trillion miles.



Nothing escapes a black holes event horizon with the possible exception of quantum effects right at the surface, Hawking Radiation, totally different effect then Merger Recoil which I'm afraid I can't explain beyond mumbling techno-speak at you. Somewhat oversimplified, when the merger takes place the new object ends up with but load of inertia from non-symmetric gravity wave emission. This probably expels a lot of black holes holes from the globular clusters they were birthed in. Don't over-mystify this though. Gravity, just like any other force, must expend energy to cause effects, it's the original thing we discovered that from back before we even knew about electricity. Take a light bulb and float it in an empty void and it doesn't move, just radiates light, break the symmetry and it will start moving. A flashlight with a really good battery will start moving off like a rocketship shoved along by it's light emissions if it's far from any gravity or friction to keep it from heading off, same as if it had a rocket motor. The only difference here, really, is that gravity is normally very symmetric, you can't really bounce it around off mirrors or shove it through a piston or rocket engine or whatever. Well, and this is a crude analogy, at the scales involved in a binary black hole merger this isn't the case anymore and it can shoot at gravity waves no symmetrically, giving it a net kick in one direction. Nothing escapes a black hole except for gravity, which obviously does, so it's a gravity drive basically, though I'm cringing to phrase it that way.



Well, not be a dick Joel but after expressing your ignorance of my field telling me you now have greater conviction in anti-gravity seems a bit excessive and weird. You might as well just have said, "I don't know anything about chemistry, but now that I've seen this endothermic chemical reaction I no longer believe in entropy"