quasi-stellar objects (qsos) and schmidt’s realization
TRANSCRIPT
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Quasi-Stellar Objects (QSOs) and Schmidt’s
Realization
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Active Galaxies
o Galaxies that have unusually bright nucleio Can have
JetsStrong variabilityStrong radio emissionBroad emission lines (like winds)
o Most are located large distance of millions and even billions LYs away
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Comparison of Spectra
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Enter the AGN Zoo
Seyfert Galaxies: • Bright pointlike
nuclei• In spirals• Two types –
1) Broad lines, X-rays2) Narrow lines, IR
• Lower luminosity than quasars
Radio Galaxies:• In ellipticals• Jets and large radio
emitting lobes (ala synchrotron emission)
Blazars:• Bright, extremely
variable• Little or no emission
lines• X-rays
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Spectra of the Zoo Animals
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Radio Galaxy Centaurus A
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Sizes of AGN
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Quasars
• Quasi-stellar radio sources: Radio sources that appear pointlike in visible light
• Extremely luminous at 1011 – 1015 Lo (note that LMW ~ 1011 Lo)
• Broad and narrow spectral lines• Lots of X-rays, UV, and blue light• Rapid variations indicate that source size
is compact (around a few pcs in extent)
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Aside on Quasars
Quasars are waysuper bright, andso they makeexcellent probesof gas throughoutdistant space
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Lyman Alpha Forest
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Quasar Spectra: Emission Lines
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Quasar Hosts
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Supermassive Black Holes
• How to get so much energy from so little space?!
• Infall of matter onto a BH can liberate gravitational energy to be emitted as light
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Ordering the Zoo
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Getting the SBH Mass
• One way to estimate the BH mass is to use the Eddington limit
• AGN are incredibly luminous, but the BH mass must be large enough so that gravity results in a net infall, hence the mass must exceed
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The Unified Model
Gas material is “fed” to a central SBH by an accretion disk
The disk glows to produce high luminosities
Magnetic fields channel some gas along poles to make jets
Zoo of AGN arise because of different SBH masses, feeding rates, and viewing perspectives
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Illustration of AGN
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Synchrotron: Magnetic Fields and
Emission
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How are ancient AGN related to galaxies
today?