Transcript The Lyman Alpha Forest

The Lyman Alpha
Forest
By Shira Mitchell
Ionized Neutral
Star
universe universe Formation
Big Bang
When did stars form?
Wavelength
What is a Spectrum?
The distribution of energy emitted by a radiant source
Intensity
Wavelength
Atoms
n=4
n=3
n=2
Photon
1216 A
Electron
excited
n=1
Hydrogen Atom Energy
Levels
Atoms
n=4
n=3
n=2
Electron
excited
n=1
Hydrogen Atom Energy
Levels
Absorption
Intensity
Wavelength
Wavelength
Wavelength
Redshift
z = Observed wavelength - Rest wavelengt
Rest wavelength
The Cosmological Redshift is a redshift caused by the
expansion of space.
Hubble’s Law
v = H*r.
v = recessional velocity
r = distance from Earth
H = Hubble's constant, 50-100
km/sec/Mpc (a megaparsec is
3,000,000 light-years)
Hubble constant sets the rate at
which the Universe is expanding.
Redshift
• z = 6 farther back to the universe’s beginnings
than z = 3
•Astronomers speak of the history of the universe
in terms of red-shifts
Quasars
Short for quasi-stellar radio sources. They
are bright active galaxy nuclei with huge
red-shifts and therefore, far distances
Quasar Spectrums
Neutral
hydrogen
absorbed
this light
Intensity
Wavelength
Quasar Spectrums
Why is there a forest?
If the universe has so much hydrogen,
why is there no trough?
The hydrogen must be ionized because
ionized hydrogen can not absorb light.
Why is the hydrogen ionized?
The radiation from stars
Therefore, to find the trough, one must
look at very very distant quasars to look
for the trough back towards the
universe’s beginnings.
Looking for the Trough
13 Apr 2000
Using the powerful Keck telescope on Mauna
Kea in Hawaii, Robert Becker and his
colleagues detected the imprint of neutral
atoms on light from quasar J1030 0524, one
of the most distant objects yet found. They
found that, over a region of the spectrum
corresponding to millions of years of cosmic
history, no light from the quasar gets through
-- it is all absorbed in intergalactic space.
Looking for the Trough
Quasar Spectrums
z=5.80
GunPeterson
Trough
z=6.28
z = 6 means it left the sources less than a billion years after the Big Bang
Why is this important?
To understand the complex
universe we live in today, it is
necessary to understand its
evolution from an early state of
simplicity.
Current Progress
• Some astrophysicists are not satisfied with
the trough in the z=6.28 quasar.
• A deeper understanding of the physics of
reionization may be required
• Some astrophysicists and cosmologists have
turned to computer simulations
Work Cited
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http://nedwww.ipac.caltech.edu/level5/Sept01/Rauch/Rauch4.html
http://www.seds.org/~rme/cosmol.html
http://astron.berkeley.edu/~mwhite/darkmatter/bbn.html
http://astron.berkeley.edu/~john/lya.html
http://nedwww.ipac.caltech.edu/level5/March01/Barcana/Bar1.html
http://www.ticam.utexas.edu/CCV/projects/DiDi/cosmo/cosmo.html
SPECTRA OF THE MOST DISTANT QUASARS ELUCIDATE THE
REIONIZATION OF THE COSMOS, By Schwarztschild, Bertram, Physics
Today, 00319228, Oct2001, Vol. 54, Issue 10 (Database: MasterFILE select)
Cosmic Coincidences: Darkmatter, Mankind and anthropic cosmology, by
John Bribbin and Martin Rees
http://www.scienceagogo.com/news/20010710012750data_trune_sys.shtml