Galactic Governors: Active Galactic Nuclei Feedback Quiz

If a supermassive black hole accretes matter, then it releases massive amounts of energy as radiation and mechanical jets. If this energy interacts with the surrounding interstellar medium, then it can heat or displace the gas. Therefore, this interaction is termed "feedback" because the black hole's activity regulates the environment that feeds it.

If stars form from cold, dense molecular gas, then any process that heats the gas or blows it out of the galaxy will prevent stars from forming. If an AGN injects heat or momentum into the gas, then the gas cannot collapse under gravity. Therefore, negative feedback suppresses star formation rather than increasing it.

If matter falls into a deep gravitational potential well, then it gains kinetic energy. If this matter forms an accretion disk, then friction converts that energy into heat and light. Therefore, the AGN’s power comes from the gravitational transformation of infalling mass into radiation.

If magnetic fields near the black hole channel plasma away from the poles of the accretion disk, then narrow beams of high-energy particles are formed. If these beams extend for thousands of light-years, they are identified as relativistic jets. Therefore, the answer is jets.

If a galaxy is surrounded by a halo of hot gas, it must cool down to flow into the galaxy and form stars. If AGN jets constantly pump energy into this halo, then the gas remains too hot to sink. Therefore, the jets maintain a "thermostatic" control that prevents the gas from fueling new star formation.

If a jet or wind passes through a region of relatively dense gas, then it creates a pressure front. If this pressure is high enough to force a marginally stable cloud to collapse, then it will lead to new star formation. Therefore, in specific local conditions, AGN activity can actually promote the creation of stars.

If an AGN provides enough energy to clear the galaxy of its cold gas supply, then the raw material for stars is gone. If the star formation rate drops to near zero, then the galaxy is said to be "quenched." Therefore, quenching describes the transition from a blue, star-forming galaxy to a "red and dead" one.

If the black hole mass (M) and the stars' orbital speeds (σ) are tightly linked, then they must have evolved together. If AGN feedback is the mechanism that links the two by limiting the growth of both the black hole and the galaxy, then this relation is the evidence. Therefore, it is the M-sigma relation.

If the question asks for AGN-specific feedback, then we must identify energy from the black hole. If jets, radiation, and winds are driven by the accretion process, they are AGN feedback. If supernovas and nebulae are stellar processes, they are not AGN-driven. Therefore, A, B, and D are correct.

If a black hole is accreting at its maximum rate, it becomes a quasar and emits enormous radiation. If this radiation pressure pushes against the surrounding gas, it creates massive, galaxy-wide outflows. Therefore, "Quasar Mode" refers to this high-luminosity, wind-dominated feedback phase.

If a black hole is "supermassive," it is millions or billions of times the mass of the Sun. If the total mass of a galaxy is trillions of times the mass of the Sun, then the black hole only accounts for about 0.1% of the total mass. Therefore, the black hole is massive but represents only a tiny fraction of the total galactic mass.

If gas is hot, then its particles move very fast and create high thermal pressure that resists gravity. If the gas cools, then the pressure drops. If the pressure is low, then gravity can win the tug-of-war and collapse the gas into a dense star. Therefore, cooling is the first step toward star birth.

If stars form in the coldest, densest regions where atoms bond into molecules (like H2​), then this is the "fuel" stage. If an AGN destroys these molecules or heats them up, the fuel is gone. Therefore, the answer is molecular.

If a thick ring of dust (torus) surrounds the accretion disk, then it blocks our view from the side. If we look from the top, we see the bright center (Quasar); if we look from the side, we only see the outer parts. Therefore, the appearance is largely a matter of geometry and orientation.

If we see empty bubbles or fast-moving gas clouds, then something must have pushed them. If a galaxy has gas but no new stars, then something must be heating that gas. If we see a bright AGN, then the energy source is present. Therefore, A, B, D, and E are all diagnostic signs.

If a Quasar is at its peak, it is the most luminous object in the universe. If it concentrates the energy of billions of stars into a space the size of our solar system, then its brightness easily overwhelms the rest of the galaxy. Therefore, the statement is true.

If hot gas in galaxy clusters is losing energy via X-rays, then it should cool down and fall into the center. If we don't see the massive amounts of cold gas this would create, then something must be reheating it. Therefore, AGN feedback is the solution to the "Cooling Flow" problem.

If galaxies merge, then gravitational torques disturb the orbits of the gas. If the gas loses angular momentum, then it falls into the deep gravity well of the central black hole. Therefore, mergers are a primary way to "turn on" an AGN.

If the AGN releases a massive amount of energy, then it pushes away the very gas it was supposed to eat. If the gas is pushed away, then there is no more matter to fall into the black hole. Therefore, AGN feedback is a self-regulating or "self-limiting" process.

If Sagittarius A* is currently "quiet" and not accreting much matter, then it is not an active AGN. If the Milky Way is still forming stars at a rate of about 1-2 per year, then it is not quenched. Therefore, our black hole is not currently providing significant feedback to our galaxy.