1. SCIENCE IN THE MEDIA
BRINGING CUTTING EDGE ASTRONOMY FROM SCIENTISTS TO STUDENTS
PUBLIC OUTREACH PROGRAM FOR THE SUZAKU SATELLITE
Students: Alfaro Estefany, Alfaro Mónica, Landeros Jaqueline, Morales Mauricio,
Morales Andrea, Samayoa Diana.
AGN:
Active Galactic Nuclei
APRIL 2013

2. CONTENT
1. What are active galactic nuclei (AGN)?
2. What is an accretion disk?
3. How do astronomers study accretion disks in AGN?
4. What does the «doughnut shaped ring» refer to?
5. Sketch of an AGN with accretion disk, black hole,
torus and jets.
6. Types of AGN
7. What is a shrouded AGN or quasar? Why can´t we
observe the shrouded AGN in the infrared?
Questions assigned under NASA´s Education and Public Outreach
Program for the Suzaku Satellite. Materials for Session 1.

3. 1. What are Active Galactic Nuclei (AGN)?
http://heasarc.gsfc.nasa.gov/docs/objects/agn/agntext.html
An artist's conception of an AGN
http://imagine.gsfc.nasa.gov/docs/science/know_l2/active_galaxies.html
Are galaxies whose nucleus (or central core) produces more
radiation than the entire rest of the galaxy.
Can have a supermassive black hole
(millions of times the mass of the Sun) at
the center or be as small as our solar system!

4. Definition:
It's the ring of gas and dust which may include material drawn from nearby
stars or even captured galaxies.
http://herschel.jpl.nasa.gov/galaxies.shtml
2. What is an accretion disk?
http://www.astro.virginia.edu
The yellowish ring of this animated
AGN represents the accretion disk
http://www.gemini.edu/gallery/v/Posters-and-
Prints/album10/GemMSF_FNL_jan22-2.jpg.html
If we make a perpendicular cut in an AGN
we will find the accretion disk extending from
a thick red ring to a bright blue flattening one

5. Accretion disks arise when material (usually gas)
is being transferred from
one celestial object to another.
An artist's concept of the accretion disk around the binary star system WZ Sge.
http://www.noao.edu/outreach/press/pr08/pr0802.html
«Accretion» means collecting of
additional material.
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/001106a.html

6. Accretion disks in AGN are hard to imagine because they
are very small and far away.
http://www.mssl.ucl.ac.uk/www_astro/research.html

7. 3. How do Astronomers study
accretion disks in AGN?
An accretion disk forms, emitting huge amounts of light across the electromagnetic spectrum
(infrared to gamma rays). The black hole plus the accretion disk produce the phenomena that
make AGN visible. http://imagine.gsfc.nasa.gov/docs/science/know_l2/active_galaxies.html
It is supermassive black holes what makes AGN
so powerful!
As the material spirals into the black hole, it heats up to enormous
temperatures and emits radiation. http://herschel.jpl.nasa.gov/galaxies.shtml
http://spiff.rit.edu/classes/phys240/lectures/blackholes/blackholes.html

8. 4. What does the “doughnut
shaped ring” refer to?
The 2 enormous powerful jets of
the AGN are fueled by the
emition and reflection of energy
at the torus, a donut-shaped gas
cloud that absorbs and reflects
energy from the accretion disk.
JET
JET
ACCRETION DISK
TORUS
http://phys.org/news/2012-03-torus-galactic-nucleus.html

9. Jets
Jets
Accretion disks arise when
material (usually gas) is
being transferred from one
celestial object to another.
"accretion" means collecting
of additional material.
Not even light can escape
their gravity, and since nothing
can travel faster than light,
nothing can escape from
inside a black hole.
http://heasarc.gsfc.nasa.gov/docs/objects/agn/agntext.html
5. Sketch of an AGN: Let´s review

10. The strong rotating magnetic
field of a black hole creates
the jets of
accelerated matter that is
emitted from the polar regions.
Jets
Jets
This torus is not as
dense, but it is much
warmer (up to thousands
of degrees) and loaded
with many more calories.
http://heasarc.gsfc.nasa.gov/docs/objects/agn/agntext.html

11. 6. Types of AGN
They are the most luminous, powerful, and
energetic objects known of at this time. They
seem to inhabit the centers of active young
galaxies and can emit up to a thousand times
the energy output of our entire galaxy.
According to Hubble’s law the redshift shows
that quasars are very distant and, because of
their distance, much older than our universe.
http://www.universetoday.com/73222/what-is-a-quasar/#ixzz2RxKCwgNw
A) QUASARS

12. They are point-likes in the sky.
Their visible light is often partially
polarized.
Their output in all wavelength bands varies
more rapidly and by a larger amount than a
quasar.
B) BLAZARS
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980116b.html
Blazars and quasars are
intrinsically the same object
— a supermassive black hole with
a surrounding
accretion disk, producing a jet —
but seen at different orientation
angles
with respect to the jet’s axis.
http://www.astronomy.com/en/News-Observing/Ask
%20Astro/2011/01/Blazar%20vs,-d-,%20quasar.aspx

13. http://physics.ucsb.edu

14. Seyfert galaxy nuclei are active galaxies
that have strong emission lines. About 2%
of spiral galaxies are Seyferts. In its nucleus
exists very hot gas which is swirling around
very rapidly.
Are a type of active galaxy; they are spiral
galaxies with extremely bright nuclei.
[Image source: Copyright © Anglo-Australian Observatory]
http://www.astronomy.ohio-state.edu/~ryden/ast162_9/notes37.html
The luminosity f the nucleus of a
Seyfert galaxy can vary wildly on
time scales of less than a month.
C) SEYFERTS

15. Japanese and NASA Satellites Unveil New Type of Active Galaxy 07.30.2007
http://web.hallym.ac.kr/~physics/course/a2u/agn/agn.htm

16. They are quasars, positioned in such a way that their dusty rings hide their light,
while others are buried in dust-drenched galaxies.
Spitzer appears to have found both types of missing quasars by looking in
infrared light. Unlike X-rays and visible light, infrared light can travel through gas
and dust.
http://www.nasa.gov/vision/universe/starsgalaxies/spitzer-080305.html
7. What is a “shrouded” AGN?

17. Who are we? We find that we live on an insignificant planet of a humdrum star lost in a galaxy
tucked away in some forgotten corner of a universe in which there are far more galaxies than
people.
Carl Sagan
SCIENCE IN THE MEDIA
BRINGING CUTTING EDGE ASTRONOMY FROM SCIENTISTS TO STUDENTS
PUBLIC OUTREACH PROGRAM FOR THE SUZAKU SATELLITE