Quasar Absorption Lines

Quasar Absorption Lines

Tracing Cosmic Structure Growth & Galaxy EvolutionOver Cosmic Time

Chris Churchill (PSU) 2






Motivations and Astrophysical ContextMg II arises in environments ranging over five decades of N(HI)

• DLAs: N(HI)>2x1020 cm-2

• LLSs: N(HI)>2x1017 cm-2

• sub-LLSs: N(HI)<6x1016 cm-2

Statistical Cross-Sections, n

Giant molecular clouds?; 0.1 L* and LSB galaxies with wide range of morphologies; intergalactic clumps; n~15 kpc; black-bottom absorption with v~200 km s-1; average C IV absorption(eg. Le Brun et al 1997; Rao & Turnshek 2000; Bouche’ etal 2000; cwc etal (II) 2000)

“Normal” HSB galaxies with >0.1 L*; n~40 kpc;complex kinematics with “high velocity” componentswith v~100-400 km s-1; range of C IV absorption(eg. Steidel et al 1994; cwc etal 1996; cwc 1997; cwc & Vogt 2000) assuming *=0.03 h3 Mpc-3

“forest clouds”? LSB galaxies?; dwarf galaxies?; few associated with HSB galaxies; mostly single unresolved clouds; n~70 kpc; sizes ~10 pc to 1 kpc; Z>0.1 solar; [/Fe]~0 to +0.5; Cf~0.15; range of C IV absorption(eg. cwc & Le Brun 1998; cwc etal ApJS 1999 ; Rigby etal 2001)

Sub-LLS

Mg II selects a wide range of astrophysical sites, which can be traced from redshift 0 to 5


What the sensitivity and resolution buy…

Steidel & Sargent (1992)

cwc (1997); cwc & Charlton (1999)


cwc & Charlton 1999



Chris Churchill (PSU) 12cwc 2001


Statistically, Profiles are Consistent with …

(Charlton & cwc 1998)Monte-Carlo Models of Absorbing Galaxies

What is probability distribution for such models?Assume ~r-2 probability distribution of clouds in disk and in haloAssume Vrot=Vinfall kinematics of clouds in disk and in halo



Voigt Profiles

Assume minimum number of components that are statistically significant (MINFIT). Parameterization does not account for asymmetric line-of-sight streaming motion.

cwc (1997); cwc, Vogt, & Charlton, ApJ, (2001)


“Weak Systems”

• Single Clouds, Wr(MgII)<0.3 , isolated in redshift

• Unresolved line widths at 6 km s-1

• Power law equivalent width distribution down to Wr(MgII)=0.02

cwc etal, ApJS (1999)Steidel & Sargent (1992)




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Quasar Absorption Lines