Cosmology and QSO’s

Edwin Hubble

Red Shift and Distance 24 Mpc1200 km/s 300 Mpc15,000 km/s 780 Mpc39,000 km/s 1220 Mpc61,000 km/s

Hubble’s Result

Modern Hubble’s Law

Raisin Cake Model

Distance Distance from Home from Home (before baking)(after baking) 1 1 cm 2 cm 2 2 cm 4 cm 3 3 cm 6 cm Velocity 1 cm/hr 2 cm/hr 3 cm/hr Velocity Distance

Hubble’s Law to get Distance Measure the red shift of a galaxy  Compute the radial velocity Use Hubble’s Law to get the distance  Assumes that red shift is caused by radial velocity and that radial velocity is caused by the universal expansion.

Universal Expansion Space-Time itself is expanding  Carries galaxies along with it Conflicting cosmologies  Big Bang  Draw the expansion back in time until space-time occupies a point (13.7 billion years ago)  Steady State  Requires continual creation of matter

Arno Penzias & Robert Wilson

Quasi-Stellar Objects Extreme red shift  Using Hubble’s Law gives great distance  Visibility at these distances requires huge luminosity Almost star-like Variable  Using Light Time Argument gives size of solar system

QSO 3C 273 and its jet Red Shift of 16% Distance 800 Mpc Luminosity of 1000 normal galaxies

The Spectrum of 3C 273

L  normally at 1216 Å The Record Red Shift

Cosmological Hypothesis QSO’s are at the distance implied by Hubble’s Law  Most distant objects in the universe  Extreme luminosities But their light variations limits the size to roughly solar system  Emit as much light as 1000 large galaxies in the space of a solar system What is the energy source?

Local Hypothesis QSO’s are nearby  Distances of normal galaxies  Luminosities don’t have to be as great What causes the Red Shift?

The Red Shift Dilemma Mass ejection  Perhaps QSO’s are matter violently ejected from galactic nuclei. Recall M87  Why only Red Shifts? Gravitational Red Shifts  Light loses energy in escaping a gravity field  E = hf = hc/  If energy decreases, wavelength increases  Impossible to get the large red shifts required

Additional facts If QSO’s are very distant, we are seeing them as they were long ago. Gravitational lens

Quasar Gravitational Lenses Q Q 0142H

Gravitational Lensing

Einstein Ring

Active Galactic Nuclei

Summary QSO are active galactic nuclei  Early stage of galaxy formation Velocity Distance QSO’s BL Lac Objects Seyfert Galaxies Normal Galaxies

Model of a Quasar Supermassive Black Hole forms in the center of a galaxy  M   Event Horizon size of solar system Thick accretion disk fuels the activity  as disk thins quasar dims

Normal Galaxies Harbor Supermassive Black Holes Measure luminosity of the nucleus  Mass in the form of stars  Brightness predicts mass Measure speed of the stars near the nucleus  Stars move under the influence of gravity  Gravity caused by mass at the nucleus Many galaxies have large, underluminous mass at the center

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