Quasars ASTR 2120 Sarazin. Quintuple Gravitational Lens Quasar

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1 Quasars ASTR 2120 Sarazin Quintuple Gravitational Lens Quasar

2 Quasars Quasar = Quasi-stellar (radio) source Optical: faint, blue, star-like objects Radio: point radio sources, faint blue star-like optical counterparts, 10% radio-loud

3 Quasars - Optical Spectra Quasars are distant, high-redshift objects 0.1 z 8

4 Quasars Quasars are distant, high-redshift objects 0.1 z 8 <z> 2

5 Quasars

6 Quasars - What Are They? Optical Properties: Very similar to Seyferts and other AGN except more luminous Radio Properties (Radio-Loud Quasars): Very similar to Radio Galaxies, have radio lobes and jets, but core is more luminous

7 Quasars - What Are They? Optical Properties: Very similar to Seyferts and other AGN except more luminous Radio Properties (Radio-Loud Quasars): Very similar to Radio Galaxies, have radio lobes, but core is more luminous Normal Galaxies Seyferts, Radio Galaxies Quasars Location: Quasars = very luminous AGNs = in centers of galaxies?

8 Quasars = Very Luminous AGNs Quasars = very luminous AGNs = in centers of galaxies? Why weren t host galaxies seen in early observations? 1. Most at high redshift, far away, host galaxies only few arcsec across 2. Seeing in ground-based observations blurs images to few arcsec 3. AGN is ~100 x luminosity of galaxy, galaxy is buried Observe with HST!!

9 Quasars Host Galaxies - HST

10 Quasars Host Galaxies - HST

11 Quasars Host Galaxies - HST

12 Quasars = Very Luminous AGNs Quasars = very luminous AGNs = in centers of galaxies

13 Theory of Quasars & AGNs What is the central engine? Size 10 2 AU ~ Solar System L 10 2 galaxies!! Mass? If held together by gravity, L < L edd = 1.5 x (M/M ) erg/s Eddington luminosity L ~ erg/s (quasar) M 10 9 M!! (quasar)

14 Theory (Cont.) Motions of Broad Line Clouds Broad lines due to Doppler shifts, v ~ 10 4 km/s Ionization of clouds d ~ 0.1 pc from central engine Clouds bound to central engine Virial theorem, PE = -2 KE M ~ v 2 d / G ~ 10 9 M!! (argument general) d v

15 Weaker AGNs Theory (Cont.) M central ~ 10 6 to 10 9 M

16 Nature of Central Object Need ~10 9 M packed into ~10 AU 1) One ~10 9 M star? BH in ~10 6 years 2) 10 9 stars (or neutron stars or BHs) collide, turn into one BH very quickly 3) 10 9 M black hole!! AGNs = super-massive black holes (SMBHs) in centers of galaxies (10 6 to 10 9 M )

17 SMBHs in Galaxies Most large galaxies have some activity Quasars most large galaxies in the past had SMBHs, would not go away Predict: Most large galaxies today have SMBH? Detect from motion of gas, stars near center of galaxy

18 SMBHs in Galaxies

19 SMBHs in Galaxies

20 SMBHs in Galaxies

21 SMBHs in Galaxies All large galaxies have a SMBH at the center M SMBH M(stars in bulge) How did this occur? Suggests that SMBH and galaxies (at least bulge parts) grew together in lockstep? Why? Feedback from SMBH affects star formation? Star formation affects supply of gas to SMBH?

22 Size of SMBH Theory (Cont.) R = R S = 2GM/c 2 = 20 AU (M BH /10 9 M ) ~ emission region from AGN

23 Energy Source Massive BH and nearby gas (emission lines) = accretion? Broad lines: M gas ~ 10 2 M t infall ~ r/v ~ (0.1 pc)/(10 4 km/s) ~ 10 1 years Ṁ ~ 10 M / yr accretion rate

24 Accretion by BH - Review Last semester showed that: L = (1/4) (R S /R) Ṁ c 2 ~ ( ) Ṁ c 2 for a BH L ~ erg/s (Ṁ /10 M / yr ) ~ L quasar

25 Accretion Disks Last semester and with galaxy formation, saw that infall of gas generally leads to rotating disk = accretion disk BH event horizon R inner = last stable circular orbit

26 Accretion Disks or Torii

27 Accretion Disks or Torii

28 Accretion Disks Temperature of inner accretion disk T disk [ L / ( 2πR 2 inner σ)] 1/4 ~ K for AGN UV emission = blue bump in spectrum BH event horizon R inner = last stable circular orbit

29 Accretion Disks Thermal emission from accretion disk radio IR visible UV X-ray

30 Accretion Disks Counter-intuitive aspect: Stellar BHs, M ~ 10 M SMBHs, M ~ 10 9 M SMBH accretion disks cooler Roughly, T disk M -1/4 BH Why do AGN have X-rays? T disk ~ K X-rays T disk ~ K UV

31 Magnetic Accretion Disks Gas in disks ionized, magnetic fields frozen in Magnetic fields carried in, strengthened 1. Magnetic fields provide means to carry angular momentum out, allow gas to accrete (Balbus-Hawley instability) 2. Accelerate relativistic particles (like pulsars) 3. Reconnection above disk (like solar flares) Make X-rays and gamma-rays

32 Magnetic Accretion Disks

33 Magnetic Accretion Disks 4. Make jets

34 Magnetically Driven Jets

35 Magnetically Driven Jets

36 Accretion Disks Can we see gas accreted by black holes? black hole event horizon

37 Accretion Disks Can we see gas accreted by black holes? Spectrally: Highly blueshifted and redshifted (Dopper and gravity) from accretion disk gas.

38 X-ray Line from Black Hole Grav. redshift Dopp redshift Dopp blueshift

39 Accretion Disks Can we see gas accreted by black holes? Spectrally: Highly blueshifted and redshifted (Dopper and gravity) from accretion disk gas.

40 Spin of Black Hole

41 Reverberation Mapping Bigger lags at larger radii, smaller velocities Map v(orbit) vs. radius

42 Athena X-ray Telescope (2028)

43 Measure Orbits of Blobs in Disk

44 Accretion Disks Can we see gas accreted by black holes? Spectrally: Highly blueshifted and redshifted (Dopper and gravity) from accretion disk gas. Imaging: Can we actually watch gas fall into black hole? Problem: Black holes are small, most far away

45 Event Horizon Telescope Sgr A* = biggest BH in angular size as seen from Earth Stellar mass BHs closer but 10 5 x smaller Supermassive black holes in large galaxies are up to 1000 x larger, but are much further away R Sch = 10 micro-arcseconds! Radio VLBI observations at 1.3 and 0.8 mm wavelength

46 Event Horizon Telescope

47 Event Horizon Telescope Alternative GR Alternative Black Hole Shadow on Accretion Disk

48 Event Horizon Telescope Accretion Disk Physics

49 Event Horizon Telescope Launching of Jets

50 Accretion Disks Can we see gas accreted by black holes? Spectrally: (and with time) Polarization: Imaging: Can we actually watch gas fall into black hole? Largest BHs in apparent size are nearby AGN Most accreted energy comes out in X-rays But, requires micro-arc-second imaging in X-rays

51 MAXIM: Micro-Arcsecond X-ray Interferometer Mission

52 X-ray Images of Black Holes with Accretion Disks

53 X-ray Images of Black Holes with Accretion Disks

54 X-ray Images of Black Holes with Accretion Disks

55 Unified AGN Model Type 1 Seyfert 1, Broad-Line Radio Galaxies, Quasars 1 Both Broad and Narrow Lines, Bright Type 2 Seyfert 2, Narrow-Line Radio Galaxies, Quasars 2 Only Narrow Lines, Fainter Blazars Almost no lines, very bright

56 Unified AGN Model Outer Accretion Disk = Accretion Torus

57 Unified AGN Model Accretion Torus Jet Perpendicular to Torus Narrow Line Clouds beyond Torus Broad Line Clouds inside of Torus

58 Unified AGN Model What we see depends on viewing angle through torus Seyfert 2, Quasar 2, Narrow Line Radio Galaxy Narrow lines, X-rays, faint over torus Seyfert 1, Quasar 1, Broad Line Radio Galaxy Broad and Narrow lines, brighter along jet Very bright, variable, lines buried in continuum

59 Why are quasars mainly at high redshift? As galaxies form in past, lots of gas around, new stars may be on orbits near BH high accretion rate With time, BH (and star formation) eat up most of fuel low accretion rate In present day Universe, evidence that mergers cause more activity new fuel for accretion

60 Gravitationally Lensed Quasars Einstein s Cross

61 Gravitationally Lensed Quasars Use time delay between images to measure distance to lens?

62 Quasar Absorption Lines Sample Intergalactic Medium Lyman alpha forest implies most of baryons in intergalactic gas (at z~2) Lyα emission line Lyα forest