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