Agn presentation
Transcript of Agn presentation
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
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 AGN7.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.
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_gal
axies.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!
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 AGNwe will find the accretion disk extending from a thick red ring to a bright blue flattening one
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
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
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
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
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
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
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
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
http://physics.ucsb.edu
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
Japanese and NASA Satellites Unveil New Type of Active Galaxy 07.30.2007
http://web.hallym.ac.kr/~physics/course/a2u/agn/agn.htm
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?
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