Download Lyman alpha forest

2013. Feb 15
Sejong University
Hee-Won Lee
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Quasar Absorption Systems
Kramers-Heisenberg Formula
Asymmetry in Scattering Cross Section
Observational Ramifications
Summary
Lyman Alpha Forest
 Lyman Limit System
 Damped Lyman Alpha System
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Residual neutral hydrogen component forming a
filamentary structure in the intergalactic medium
Appears in the absorption profile blueward of
Lyman alpha of a background quasar
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Defined by N_HI>2X10^20
cm^-2
Maybe disk component of a
galaxy intervening the
sightline
Contain most neutral
hydrogen providing raw
material for star formation
during the most of the
cosmic time from the
reionization era.
Important probe for cosmic
chemical evolution
May contain some dust.
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Convolution of a Gaussian and
a Lorentzian
The core part is approximately
Gaussian whereas the wing
part is Lorentzian.
Resonance line shape is
approximately Lorentzian in
the near wing part.
Far wing part, deviation from a
Lorentzian is observed
depending on the atomic
wavefunction.
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An atom is regarded as a
simple harmonic
oscillator.
Scattering of
electromagnetic
radiation by an atom is
analogous to an
externally driven simple
harmonic oscillator.
Lorentzian behavior is
universally obtained.
Quantum mechanical
correction is given in
terms of the oscillator
strength.
Initial State: Incident Photon+Atom in Ground
State
 Intermediate State : Atom in an excited np state.
 Final State: Outgoing Photon+Atom in Ground
(or Excited) State
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Admits wavefunctions in an analytically
closed form.
 Electric dipole operator connecting two
eigenstates of hydrogen has matrix
elements given in terms of confluent
hypergeometric function.
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Redward
asymmetry
around Lyman
alpha.
 Blueward
asymmetry
around Ly beta
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GRB 080607
N HI=5X10 22 cm-2
Inadequecy of Voigt profile
fitting
Accurate atomic physics is
necessary.
Accurate atomic physics is required for
careful analysis of DLAs, which are
important in study of star formation process.
 GRBs may provide another aspect of star
forming history.
 Gunn-Peterson troughs should be analyzed
using accurate atomic physics.
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