slide1 l.
Download
Skip this Video
Download Presentation
Quasars and Other Active Galaxies

Loading in 2 Seconds...

play fullscreen
1 / 40

Quasars and Other Active Galaxies - PowerPoint PPT Presentation


  • 201 Views
  • Uploaded on

Quasars and Other Active Galaxies. In this chapter you will discover…. 5-10% of galaxies unusually bright, called active galaxies The most distant objects we can see: quasars Evidence for unusual spectra and small volumes Models of quasars Tests of those models closer to the Milky Way

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Quasars and Other Active Galaxies' - wesley


Download Now An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
in this chapter you will discover
In this chapter you will discover…
  • 5-10% of galaxies unusually bright, called active galaxies
  • The most distant objects we can see: quasars
    • Evidence for unusual spectra and small volumes
    • Models of quasars
    • Tests of those models closer to the Milky Way
  • Extremely powerful BL Lac objects
  • Supermassive black holes are central engines for radio galaxies, quasars, Seyfert galaxies, & BL Lac objects
essay questions to know
Essay Questions to Know!
  • What are active galaxies? How do active galaxies produce their energy? How do we know?
  • What are quasars, and where are they found? What do they tell us about the universe?
active galaxy types
Active Galaxy Types
  • Seyfert Galaxies: Spirals with very bright centers
  • Radio Galaxies: Ellipticals with huge emissions of radio energy in “lobes”
  • Quasars: Very tiny, distant objects All have very bright, active galactic nucleii
slide5

Active Galactic Nuclei

  • Seyfert Galaxies
    • spiral galaxies with incredibly bright, star-like center (nucleus)
    • they are very bright in the infrared
    • their spectra show strong emission lines

Circinus

slide6

Active Galactic Nuclei

  • Seyfert Galaxies
    • spiral galaxies with incredibly bright, star-like center (nucleus)
    • very bright in the infrared
    • their spectra show strong emission lines

Circinus

The luminosity can vary by as much as the entire brightness of the Milky Way Galaxy!!

slide9

Cygnus A Radio Image

635 Million light years away, and still one of the brightest radio sources in the entire sky!

active galactic nuclei
Active Galactic Nuclei
  • Radio Galaxies|
    • galaxies – usually giant ellipticals - which emit large amounts of radio waves
    • the radio emission come from lobes on either side of the galaxy; not the galaxy itself
radio galaxy lobes
Radio Galaxy Lobes

These lobes are swept back because the galaxy is moving through an intergalactic medium.

slide13

X-ray/Radio Image of Centaurus A

X-ray isblue; radio is red

slide15

BL-Lac Objects

Superbright Elliptical Galaxy

slide16

Quasars

A peculiar Star-like object, emitting lots of radio waves? But not with a stellar spectral fingerprint!

quasar spectra
Quasar Spectra
  • Star-like objects
  • spectra that look nothing like a star
  • Faint Hydrogen lines…
  • VERY red-shifted!
quasar observations
Quasar Observations
  • emit light at all wavelengths
    • A hot dense source?
  • occasionally (~10% of time) VERY strong radio sources
  • Associated with jets from galaxies in clusters
quasars
Quasars
  • Show enormous redshifts VERY far away by Hubble’s Law
  • Show extreme variability  VERY small, in scales of a light-hours to light years ….and so….

Quasars must be some of the most powerful objects we know of in the universe!

quasar distribution
Quasar Distribution
  • Seen at greatest distances (earliest history of the universe!)
  • Quasar behavior in some nearer clusters
a theoretical model quasar
Atheoretical model quasar
  • Must account for observations:
    • Small Size
    • Enormous energy output across spectrum
    • Source of Jets
    • Similar behavior in galaxies in clusters
    • Some radio synchrotron emission (indicating magnetic field)
    • Full spectrum emission
a quasar model
A quasar model…
  • Supermassive Black Hole formed as Galaxies are born…
  • Pulling in gas, dust, and stars into accretion disk
  • Generating jets of X-ray radiation for millions of years
  • “Re-ignited” during collisions/mergers of galaxies
quasar energy source
The energy is generated from matter falling onto a supermassive black hole…

1.2 x 109 M for NGC 4261

3 x 109 M for M87

…which is at the center (nucleus) of the galaxy.

Quasar Energy Source?
quasar energy source28
Quasar Energy Source?
  • Matter swirls through an accretion disk before crossing over the event horizon.
  • Gravitational energy lost like E = mc2
    • 10 – 40% of this is radiated away
  • Process is very efficient
a quasar model29
A quasar model…
  • Works to explain quasars
    • Even Supermassive Black holes are TINY
    • Accretion Disk generates thermal spectrum, jets, magnetic fields
    • Highly variable as mass is pulled in

and…

  • Works for active galaxies, too!
slide30

Theory

Observation

slide35
Formation of the Jets

magnetic fields in accretion disks are twisted

they pull charged particles out of the disk and accelerate them like a slingshot

particles bound to magnetic field; focused in a beam

Quasar Jets

slide36

Model Quasar Accounts for Other Observations, too

  • Orientation of jet beam determines what we see:
    • if beams points at us, we see a quasar
    • if not, the molecular clouds/dust of the galaxy block our view of the nucleus
    • so we see a radio galaxy or Seyfert galaxy
    • lobes are where jets impact intergalactic medium
hubble space telescope shows us that quasars do live in galaxies they are active galactic nuclei
Hubble space telescope shows us that quasars do live in galaxies…they are Active Galactic Nuclei!
evidence quasars are distant
Evidence Quasars are distant?
  • Hubble’s Law
  • Association with Galaxies in clusters
  • Gravitational Lensing