1. QUASARS Monsters of the ancient Universe Professor Jill Bechtold Steward Observatory Tucson Amateur Astronomers, Dec. 6, 2002

2. QUASARS What are they? Why do we think they are supermassive black holes? How can we see anything from a black hole? What do they look like in the X-ray and radio? What are they good for? Quasar absorption lines Gravitational lensing Cosmic evolution of quasars What do we see? How can we understand what we see?

3. What are quasars? Quasars are supermassive black holes, found in the centers of galaxies Mass of quasar black holes = 10 6 – 10 9 solar masses Stars and gas fall into the black hole and shine in an “accretion disk” Million times brighter than all the stars in a big galaxy like the Milky Way

4. How can we “see” a black hole? We see accretion of gas and stars As material is sucked in by gravity, it can’t fall directly in, but circles the hole in an “accretion disk” The material in the accretion disk heats up to 20,000 – 100,000 degrees The radiation from the disk lights up clouds, making emission lines in the spectrum We see accretion of gas and stars As material is sucked in by gravity, it can’t fall directly in, but circles the hole in an “accretion disk” The material in the accretion disk heats up to 20,000 – 100,000 degrees The radiation from the disk lights up clouds, making emission lines in the spectrum

5. Artist’s illustration of accretion disk

6. How do we know there are black holes in quasars? Quasars are very luminous – many times all the stars in the Milky Way Their light varies on timescales of minutes: therefore the emitting regions have to be very small – the size of the solar system Fusion (as in stars) won’t work Release of gravitational energy by accretion onto a black hole Quasars are very luminous – many times all the stars in the Milky Way Their light varies on timescales of minutes: therefore the emitting regions have to be very small – the size of the solar system Fusion (as in stars) won’t work Release of gravitational energy by accretion onto a black hole

7. Although we can see disk shaped features in the cores of some nearby Seyfert galaxies, we can’t image the accretion disk directly

8. In optical photographs, quasars look like stars because they are so far away. Mostly we infer the structure of quasars from spectra

9. Seyfert Galaxy, or quasar in a nearby spiral galaxy Radio source in center allows us to map the motion of the accretion disk directly Seyfert Galaxy, or quasar in a nearby spiral galaxy Radio source in center allows us to map the motion of the accretion disk directly NGC 4258

10. Radio MASERS in NGC 4258

11. Our Galaxy, the Milky Way

12. Sagitarius A* A monster “snacking” Center of the Milky Way has a black hole 2.6 million times the mass of the Sun Bright radio, IR and X-ray source X-ray flare seen with Chandra X-ray telescope Chandra X-ray image the center of our Milky Way Galaxy

13. Adaptive Optics Movie of Stars in Milky Way Galactic Center Star motions imply that there is a 100,000 solar mass black hole in the center of the Milky Way.

14. Centaurus A Elliptical galaxy Dust lane Very bright radio source and X-ray source 11 million light years away – nearest radio- loud quasar Elliptical galaxy Dust lane Very bright radio source and X-ray source 11 million light years away – nearest radio- loud quasar

15. Radio Jet in Centaurus A

16. Chandra X-ray Image of Cen A X-ray jet and X-ray binaries

17. Synchrotron JETS Relativistic electrons (velocity ~ c) trapped by magnetic field Beads on wires, rotating, get flung out? Relativistic electrons (velocity ~ c) trapped by magnetic field Beads on wires, rotating, get flung out?

24. VSOP – Radio Interferometry from SPACE

26. Monitor Jet in Core

27. SUPERLUMINAL MOTION apparent v >> c

28. Models of Jet Propagation LAMINAR TO TURBULENT FLOW

29. QUASAR EVOLUTION Quasar activity peaked about 10 billion years ago

32. Local Galaxy Collisions

34. Double X-ray Source in NGC 6240: Two Supermassive Black Holes? HST Optical (Stars and dust) Chandra X-ray (hot gas and double nuclei)

36. Search for dead quasars in nearby galaxies: look at star motions

38. Black holes “know” where they live

39. Globular Clusters may have intermediate mass black holes

40. What does the accretion disk really look like?

43. Iron Line in X-rays at 6.7 keV Arises nearest black hole Shape of line looks like what you expect for an accretion disk around a massive black hole Iron Line in X-rays at 6.7 keV Arises nearest black hole Shape of line looks like what you expect for an accretion disk around a massive black hole

44. PKS 1157-143 Most distant X-ray jet Chandra X-ray image Radio is very weak Not synchrotron emission Chandra X-ray image Radio is very weak Not synchrotron emission

45. HST Optical Image + Chandra X-ray Image