14Conditions in Protogalactic Cloud? Spin: Initial angular momentum of protogalactic cloud could determine size of resulting disk
15Conditions in Protogalactic Cloud? Density: Elliptical galaxies could come from dense protogalactic clouds that were able to cool and form stars before gas settled into a diskElliptical vs. Spiral Galaxy Formation
16Start with the Mildly Active or Peculiar Galaxies STARBURST galaxies 's of stars forming per year, but spread over some 100's of parsecs.Other PECULIAR galaxies involve collisions or mergers between galaxies.Sometimes produce strong spiral structure (e.g. M51, the "Whirlpool")Sometimes leave long tidal tails (e.g. the "Antennae" galaxies)Sometimes leave "ring" galaxy structures--an E passing through a S.Sometimes see shells of stars around Es
17Peculiar Galaxies: Starburst (NGC 7742) , Whirlpool (M51), Antennae (NGC 4038/9) in IR, Ring (AM )
18Colliding Galaxies “Cartwheel” ring galaxy Antennae, w/ starbursts and a simulation: a collision in progressCollision Simulation Movie
19Collisions may explain why elliptical galaxies tend to be found where galaxies are closer together Stat here on 4/14
20Giant elliptical galaxies at the centers of clusters seem to have consumed a number of smaller galaxies
21Starburst galaxies are forming stars so quickly they would use up all their gas in less than a billion years
224 MAIN CLASSES of AGN Radio Galaxies Quasars Seyfert Galaxies BL Lacertae Objects (or Blazars with some Quasars and some Radio Galaxies)All are characterized by central regions with NON-THERMAL radiation dominating over stellar (thermal) emission
23Thermal vs. Non-Thermal Spectra. Normal mostly from stars, Thermal vs. Non-Thermal Spectra Normal mostly from stars, Active mostly synchrotron
24RADIO GALAXIES All are in Elliptical galaxies Two oppositely directed JETS emerge from the galactic nucleusThey often feed HOT-SPOTS and and LOBES on either side of the galaxyRadio source sizes often 300 kpc or more --- much bigger than their host galaxies.Head-tail radio galaxies arise when jets are bent by the ram-pressure of gas as the host galaxy moves through it.For powerful sources only one jet is seen: this is because of RELATIVISTIC DOPPER BOOSTING: the approaching jet appears MUCH brighter than an intrinsically equal receding jet since moving so FAST;Can yield CORE DOMINATED RGs
29QUASAR PROPERTIESQUASI-STELLAR-OBJECT: (QSO): i.e., it looks like a STAR BUT: NON-THERMAL SPECTRUM UV excess (not like a star)BROAD EMISSION LINES Rapid motionsVERY HIGH REDSHIFTS not a star, but FAR away. The current (2008) convincing record redshift is z = 6.4, i.e., light emitted in FAR UV at 100 nm is received by us in the near IR at 740 nm!HUGE DISTANCES VERY LUMINOUS
30NEWER QUASAR DISCOVERIES Only about 10% are RADIO LOUDMost show some VARIABILITY in POWEROVV (Optically Violently Variable) QUASARS change brightness by 50% or more in a year and are highly polarizedQUASARS are AGN: surrounding galaxies detected, though small nucleus emits times MORE light than 1011 stars! “Brighter than a TRILLION suns”
31Quasar 3C 273Radio loudRare OPTICAL jet, but otherwise looks like a starRelatively nearby quasar
35Thought QuestionWhat can you conclude from the fact that quasars usually have very large redshifts?A. They are generally very distantB. They were more common early in timeC. Galaxy collisions might turn them onD. Nearby galaxies might hold dead quasars
36Thought QuestionWhat can you conclude from the fact that quasars usually have very large redshifts?A. They are generally very distantB. They were more common early in timeC. Galaxy collisions might turn them onD. Nearby galaxies might hold dead quasarsAll of the above!
37Birth of a Quasar Movie Fast variability implies small size Immense powers emerging from a volume similar to the solar system!
38SEYFERT GALAXIES Sa, Sb galaxies with BRIGHT, SEMI-STELLAR NUCLEI NON-THERMAL & STRONG EMISSION LINESVARIABLE in < 1 yr COMPACT COREType 1: Broad Emission lines (like QSOs), strong in X-raysType 2: Only narrow Emission lines, weak in X-raysAbout 1% of all Spirals are SEYFERTS, soEither 1% of all S's are always Seyferts OR100% of S's are Seyferts for about 1% of the time (MORE LIKELY)OR 10% of S's are Seyferts for about 10% of the time (or any other combination of fraction and lifetime)Start here on 11/29 and 11/30
39A Seyfert and X-ray Variability Circinus, only 4 Mpc away; 3C 84
40More About Seyferts Seyferts are weak radio emitters. CONCLUSIONS ABOUT SEYFERTS Fundamentally, they are WEAKER QSOsType 1: we see the center more directly Type 2: dusty gas torus blocks view of the center
41BL Lacertae ObjectsNON-THERMAL SPECTRUM: Radio through X-ray (and gamma-ray)Radiation strongly POLARIZEDHIGHLY VARIABLE in ALL BANDSBut (when discovered) NO REDSHIFT, so distances unknownLater, surrounding ELLIPTICAL galaxies foundCONCLUSION: greatly enhanced emission from the AGN due to RELATIVISTIC BOOSTING of a JET pointing very close to us.BL Lacs + OPTICALLY VIOLENTLY VARIABLE QUASARS ARE OFTEN CALLED BLAZARS
42AGN CONTAIN SUPERMASSIVE BLACK HOLES (SMBHs) KEY LONGSTANDING ARGUMENTS:ENERGETICS: Powers up to 1048 erg/s (1041W) Even at 100% efficiency would demand conversion of about 18 M /yr (=Mdot) into energy.Nuclear processes produce < 1% efficiency.GRAVIATIONAL ENERGY via ACCRETION can produce between 6% (non-rotating BH) and 32% (fastest-rotating BH),and the Luminosity isL = G MBH Mdot / R,with R the main distance from the Super Massive Black Hole (SMBH) where mass is converted to energy.
43Time Variability tVAR = R / c tVAR = 104 s R = 3 x 1014 cm = 10-4 pc For L = 1047 erg/s,M_dot = 10 M /yr we get MBH = 3 x 108 M and RS = 9 x 1013 cmSo, R = 3 RSMUTUALLY CONSISTENT POWERS AND TIMESCALES.
44RECENT OBSERVATIONAL SUPPORT The Hubble Space Telescope has revealed that star velocities rise to very high values close to center of many galaxies and gas is orbiting rapidly, e.g. M87Disks have been seen via MASERS in some nearby Seyfert AGN.VLBI: radio jets formed within 1 pc of center.There are several other more technical lines of evidence also supporting the SMBH hypothesis for AGN.
45Rapidly Rotating Gas in M87 Nucleus M87 zoom toward black hole
46Direct Evidence for Rotating Disk Masers formed in warped disk in NGC 4258 (and a few other Seyfert galaxies)
47Evidence for Supermassive Black Holes NGC 4261: at core of radio emitting jets is a clear disk~300 light-yrs across and knot of emission near BH
49UNIFIED MODELS FOR AGNThree main parameters: MBH; the accretion rate, M_dot, and viewing angle to the accretion disk axis, Main ingredients:SMBH > 106 M10-5 pc < accretion disk < 10-1 pc (AD)broad line clouds < 1 pc (BLR)thick, dusty, torus < 100 pcnarrow line clouds < 1000 pc (NLR)sometimes, a JET (usually seen from < 102 pc to maybe 106 pc!)Start here on 4/16
50Unification for Radio Quiet and Radio Loud High MBH, M_dot: small: QSO is seen including AD and BLR large: only NLR plus radiating torus: seen as UltraLuminous InfraRed Galaxies (ULIRGs)Low MBH, M_dot: small: Seyfert Type 1 big: Seyfert Type 2RADIO LOUD (Jets)High MBH, M_dot: very small: Optically Violently Variable Quasar small: radio loud quasar (QSR) large: classical double radio galaxy (FR II type)Low MBH. M_dot: very small: BL Lac object small: broad line radio galaxy (FR I type) large: narrow line radio galaxy
51Different AGN from Different Angles Luminous: Quasars seen close to perpendicular to disk and Ultraluminous Infrared Galaxies near disk planeWeaker: Type 1 or Type 2 SeyfertsIf jets are important:BL Lacs along jet axis,Quasars at modest angles & Radio Galaxies at larger angles
52Black Holes in Galaxies Many nearby galaxies – perhaps all of them – have supermassive black holes at their centersThese black holes seem to be dormant active galactic nucleiAll galaxies may have passed through a quasar-like stage earlier in time
53Galaxies and Black Holes Mass of a galaxy’s central black hole is closely related to mass of its bulge