Quasars are supermassive black holes, found in the centers of galaxies Mass of quasar black holes = solar masses

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1 Quasars

2 Quasars are supermassive black holes, found in the centers of galaxies Mass of quasar black holes = solar masses Stars and gas fall into the black hole and shine in an accrecon disk billion Cmes brighter than our Milky Way Million Cmes brighter than all the stars in a big galaxy like the Milky Way Most distant objects in the Universe we've discovered are Quasars. About 10% of the quasars we see also have very bright radio jets - - plasma accelerated to near the speed of light About 10 billion years ago, the Universe was filled with bright quasars, but now bright quasars are very rare

3 How can we see a black hole? We see accre%on of gas and stars As material is sucked in by gravity, it can t fall directly in, but circles the hole in an accrecon disk The material in the accrecon disk heats up to 20, ,000 degrees The radiacon from the disk lights up clouds, making emission lines in the spectrum

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

5 Quasars, AcCve GalacCc Nuclei & Related Objects Any object where the energy output not related to ordinary stellar processes Powered by mass accrecon onto supermassive black holes Radio Galaxies Radio- Loud Quasars BL Lac s, Blazars, OVV s (OpCcally Violent Variables) Radio- Quiet QSOs (Quasi- Stellar Objects) Seyfert 1 & 2 Galaxies LINERS (Low ionizacon nuclear emission line regions) Starburst galaxies; ULIRGS (Ultraluminous IR Galaxies)

6 How do we know there are black holes in quasars? Quasars are very luminous many Cmes all the stars in the Milky Way Their light varies on Cmescales of minutes: therefore the emifng regions have to be very small (on the order of a few light minutes) the size of the solar system Fusion (as in stars) won t work Release of gravitaconal energy by accrecon onto a black hole

7 The The Central Engine Fermilab Colloqium 29 October 2003

8 1978 NASA launches the Einstein X-ray Observatory. They find that virtually every Seyfert and Quasar is an X-ray source. In fact, if we had X-ray sensitive eyes, the night sky would be filled with quasars: Rosat X- ray sky

9 Very Large Array (of radio telescopes) in New Mexico Acts like One telescope The size of the Array Very good SpaCal resolucon i.e. very sharp Pictures The Hubble Space Telescope of Radio Astronomy

10 Typical Radio image of a Radio- Loud Quasar Synchrotron Emission Remember only 10% of quasars are Radio- Loud

11 Radio Jets in Quasars: SYNCHROTRON RADIATION The radio photons are made by high speed (relacviscc, so v ~ c) electrons spiraling around magnecc field lines (synchrotron radiacon).

12 SYNCHROTRON EMISSION

13 Centaurus A EllipCcal galaxy Dust lane Very bright radio source and X- ray source 11 million light years away nearest radio- loud quasar

14 Radio Jet in Centaurus A OpCcal: starlight Radio: Synch.

15 Chandra X- ray Image of Cen A X- ray jet and X- ray binaries Plus diffuse hot, 10 million degree gas

16 X- rays from very hot gas: Bremsstrahlung Radia1on Bremsstrahlung: Braking RadiaCon All the atoms are ionized, so just have protons, other bare atomic nuclei and electrons Electrons fly by proton, slow down and emit a photon:

17 Synchrotron Emission: radio light from JETS Rela1vis1c electrons (velocity ~ c) trapped by magne1c field Beads on wires, rota1ng, get flung out?

18 More pictures of radio jets

24 Monitor Jet in Core

25 Jet in M87, big ellipccal galaxy in the Virgo Cluster

26 SUPERLUMINAL MOTION apparent v >> c

27 1990s NASA's new Compton Gamma Ray Observatory observes that some quasars and active galaxies are powerful sources of high energy gamma rays that vary in timescales of days. These objects are blazars like BL Lac. Gamma- ray

29 Blazars vary Blazars all show superluminal expansion in their cores.

1995 Radio astronomers from Harvard and Japan use very long baseline interferometry to measure the rotation velocities of radio emission lines from very bright water "masers" in

30 1995 Radio astronomers from Harvard and Japan use very long baseline interferometry to measure the rotation velocities of radio emission lines from very bright water "masers" in molecular clouds near the nucleus of Seyfert galaxy NGC 4258 and find that these clouds are orbiting a black hole with mass of 35 million solar masses. Miyoshi et al Nature, 373, 127

31 NGC 4258 Seyfert Galaxy, or quasar in a nearby spiral galaxy Radio source in center allows us to map the mocon of the accrecon disk directly

Water Molecule MASERS Masers are like Lasers but the M stands for Molecule or Microwave LASER and is an acronym for light amplificacon by s1mulated

32 Water Molecule MASERS Masers are like Lasers but the M stands for Molecule or Microwave LASER and is an acronym for light amplificacon by s1mulated emission of radiacon. SIMULATED emission: there is a higher probability for the atom or Molecule to emit light if there are already photons with the same energy

34 MASER/LASER AnimaCon PHYSICS of Lasers and Masers was formulated by Albert Einstein

35 Seyfert Galaxy (Quasar) NGC 4258 Keplerian RotaCon Curve: Masers in AccreCon disk Velocity Of maser knots Distance from central Black hole

2000-2008 The Sloan Digital Sky Survey surveys 8400 square degrees of the northern sky. The final dataset contains imaging and spectra of 930,000 galaxies, 120,000 quasars and 225,000 stars.

36 The Sloan Digital Sky Survey surveys 8400 square degrees of the northern sky. The final dataset contains imaging and spectra of 930,000 galaxies, 120,000 quasars and 225,000 stars. As an offshoot of the SDSS, X. Fan and collaborators find the highest redshift quasars known, and show that the intergalactic medium was neutral for z>6.2 or so. The 2.5m SDSS telescope in Apace Point, N.M.

37 Z>5.7 quasars from the SDSS Z=5.80 Z=5.82 Z=5.99 Z=6.28 Fan et al. 2000, 2001

38 QUASAR EVOLUTION Quasar ac1vity peaked about 10 billion years ago

39 2002- present Studies with HST show that every nearby spiral bulge or Elliptical galaxy Quasar contains a dead EvoluCon black hole. The mass of the black hole is proportional to the mass of the galaxy so the formation and evolution of black holes must be related to the formation and evolution of galaxies. Black holes know where they live

40 Search for dead quasars in nearby galaxies: look at star mocons

42 Black hole v. spheroid mass they know about each other! Haring & Rix 2003 The Kormendy RelaCon Mbh=0.006MGal

43 Double X- ray Source in NGC 6240: Two Supermassive Black Holes? HST Op1cal (Stars and dust) Chandra X- ray (hot gas and double nuclei)

1970s- 1990s High efficiency detectors, large ground-based telescope, and the launch of Hubble allow astronomers to get high resolution spectra of quasars, and study the absorption-lines

44 1970s- 1990s High efficiency detectors, large ground-based telescope, and the launch of Hubble allow astronomers to get high resolution spectra of quasars, and study the absorption-lines from intervening gas: intergalactic hydrogen, and the ISM of intervening galaxies Lyman- alpha forest: absorpcon lines in quasar spectra From intergalaccc hydrogen gas from which galaxies form

45 Lyman alpha forest: Sheets and filaments of IntergalacCc Gas Ionized by metagalaccc UV radiacon from quasars and starburst galaxies Courtesy R. Cen

46 Other absorpcon lines in quasar spectra are caused by interstellar Gas in galaxies that are too faint to see.

47 Quasars: Summary Quasars are supermassive black holes in the centers of galaxies, which are extraordinarily bright because they are accrete gas and stars Quasars are bright X- ray emi{ers, and gamma ray emi{ers. The jets in quasars are bright radio sources, where relacviscc electrons emit radio waves by the synchrotron process, which is highly polarized. Diffuse X- ray emission is from the thermal bremmstrahlung process. Quasar absorpcon lines give us informacon about intergalaccc gas from which galaxies formed. Masers in a few nearby quasars show a disk which is rotacng in Keplerian mocon around a supermassive black hole. Otherwise the inference that black holes power quasars comes from variability studies which imply that the emifng regions are very small. Quasar accvity peaked about 10 billion years ago. The mass of the bulge of quasar host galaxies correlates with the black hole mass, at least for nearby dead quasars, implying that galaxy formacon and quasar formacon are linked.

Active Galaxies & Quasars

Active Galaxies & Quasars Normal Galaxy Active Galaxy Galactic Nuclei Bright Active Galaxy NGC 5548 Galaxy Nucleus: Exact center of a galaxy and its immediate surroundings. If a spiral galaxy, it is the