Asymmetric Absorption Profiles around Ly alpha Lyman beta

2013. Feb 15Sejong University

Hee-Won Lee

Content Quasar Absorption Systems Kramers-Heisenberg Formula Asymmetry in Scattering Cross Section Observational Ramifications Summary

Quasar Absorption Systems

Lyman Alpha Forest Lyman Limit System Damped Lyman Alpha System

Lyman alpha forest

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

Damped Lyman Alpha Systems

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 reion-ization era.

Important probe for cosmic chemical evolution

May contain some dust.

Chemical Evolution with DLAs

Voigt Profile Convolution of a Gaussian and a

Lorentzian The core part is approximately

Gaussian whereas the wing part is Lorentzian.

Resonance line shape is approx-imately Lorentzian in the near wing part.

Far wing part, deviation from a Lorentzian is observed depend-ing on the atomic wavefunction.

Resonance Scattering in Classical Physics

An atom is regarded as a simple harmonic oscilla-tor.

Scattering of electromag-netic radiation by an atom is analogous to an exter-nally driven simple har-monic oscillator.

Lorentzian behavior is universally obtained.

Quantum mechanical cor-rection is given in terms of the oscillator strength.

Qunatum Mechanical Description

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

Kramers-Heisenberg Formula

Hydrogen Atom

Admits wavefunctions in an analytically closed form.

Electric dipole operator connecting two eigenstates of hydrogen has matrix ele-ments given in terms of confluent hyperge-ometric function.

Expansion of K-H Formula around Ly Alpha

Expansion of K-H Formula around Ly beta

Exact Cross Section around Ly alpha and beta

Asymmetry around Ly alpha and Ly beta

Redward asym-metry around Lyman alpha.

Blueward asymmetry around Ly beta

Transmission Coefficients

Absorption Center shift

Voigt fit using shifted centers (ly a)

Shifted Voigt function (ly b)

Extreme HI content toward grb GRB 080607 N HI=5X10 22 cm-2 Inadequecy of Voigt profile fitting Accurate atomic physics is neces-

sary.

Why?

Summary and Discussion

Accurate atomic physics is required for care-ful 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.