1	Active Galaxies, Quasars, & Large-Scale Structure in the Early Universe Lecture 13 Ay-1
2	Active galaxies
3	Categories of Active Galaxies Seyfert galaxies like normal spirals but with bright (> 10¹¹L_¤), point-like (rapid variability) nuclei; dusty - 75% radiation in infrared, internal Doppler motions 1000 - 3000 km /s Radio galaxies (10%) often appear like elliptical galaxies; BUT strong radio emission (lobes) outside galactic nucleus, extend 50 - 1000 kpc ! ® result from very energetic processes in nucleus e.g. Centaurus A: visible ® seems like E2, 500 kpc diameter All active galaxies vast amounts of energy emitted from or generated in central compact nucleus - jets common (indicate bursts of activity), probable origin? – galaxy-galaxy interactions
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5	Quasars many strong radio sources (3C catalog) - no obvious optical counterparts 3C48 (1960), 3C273 (1962) identified with faint star-like optical sources – but spectra inexplicable 1963 - Schmidt & Greenstein (Caltech) ® highly redshifted hydrogen Balmer lines 3C 273 at 620 Mpc , 3C 48 at 1300 Mpc (from Hubble Law) (recessional velocity of 3C 48 ~ 1/3 velocity of light) L > 10¹² L_¤!! light varies within 1 month ® size < 0.1 lyr ¯ QUAsi-Stellar radio sources – QUASARS now Quasi-Stellar Objects QSOs
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10	Blazars/Quasars synchrotron radiation ® jets of relativistic particles blazars: double radio sources seen end-on motions superluminal – appear to exceed speed of light usually 5 to 10 x c superluminal motions observed in some quasars (1 to 5 x c) 3C 273: radio emission separating at 0.001 arsec/yr ® 10 x 3 x 10⁵ km/s !
11	Superluminal Motion?
12	Other viewing angle effects
13	How are active galaxies powered? Have to account for: high luminosities non-stellar radiation variability ® compact nuclei (£ 1 pc diam) explosive activity – jets rapid internal motions (broad emission lines) ¯ accretion onto a compact object ® supermassive black hole millions – billions x M_¤ can have radius 20 AU infalling material ® gravitational energy® kinetic energy® thermal energy® radiation jets accompany accretion disks
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16	Cosmology : structure and evolution of the universe Questions and issues: size of universe - infinite or finite? structure – hierarchies? age - limited or forever (in future and in past)? evolution - relative amounts of matter and radiation? atomic composition? Speed of light finite ® we can effectively look back in time!!
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18	Big Bang –creation of universe Our cosmic particle horizon = how far can we detect phenomena within age of universe R_horiz = t_univ x c Can’t see stars further than 14 Blyrs & redshifts decrease photon energy (even harder to detect) Horizon increasing Planck time t_p =( Gh/c⁵)^1/2 = 1.35 x 10^-43 secs time, space behave as today Between Big Bang and Planck time nothing known
19	Cosmic Microwave Background (CMB) – radio emission filling all of universe - “sound” of Big Bang
20	CMB istropic® universe isotropic
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