The metallicity of the high column density Lyforest at 2 < z < 3.5

Tae-Sun Kim Col: Bob Carswell

Institute of Astronomy

Metal linesCIV, SiIV, MgII, FeII

HI lines ( < 1017 cm-2)

QSO absorption line systems: the Ly- forest highly ionised, low density absorption lines

QSO

Cen’s Webpage

Observations:

• ~90% of clouds with N(HI) > 1015 cm-2 are enriched with CIV (up to z ~ 5)

• Highly ionised => ionisation correction• Relatively cool, T < 105 K• Highly inhomogeneous, density-dependent, z-independent

• [C/H] = -3.47 + 0.08 (z - 3) + 0.65 (log – 0.5)

(Schaye et al. 2003)

Pettini (2004)

Galaxies: spirals?

IGM

?

Metal enrichment of the IGM: Galaxy-IGM interplay

• Metallicity of systems N(HI) = 1015-19 cm-2

• Redshift dependence?

N(HI) = 1015-19 cm-2

Difficulties for N(HI) = 1015-17 cm-2 zzzzzzzz

• Saturation

• Not many available ionic transitions

• Sensitive to the UV background

Most ionic lines are not saturated!!

Observations and Data reduction

QSOs zem Forest redshifts # of systems

PKS1448232 2.219 1.9862.175 1/0/1PKS023723 2.223 1.9862.179 1/0/1HE22172818 2.406 1.9862.360 3/0/3HE11221648 2.412 1.9862.365 2/0/2Q0329385 2.435 1.9862.389 2/0/2Q0002422 2.767 2.1832.717 6/3/6PKS2126158 3.280 2.6693.222 12/3/5

• VLT/UVES Archive data• R 45000, S/N 3050• Voigt profile fitting with VPFIT: NHI = cm-2

N(HI) = 1015.10 cm-2

Nor

mal

ized

flu

x

Nor

mal

ized

flu

x

N(HI) = 1015.81 cm-2

N(CIV)/N(HI) vs N(HI)

◊ : Songaila & Cowie (1996) : z ~ 3*

With other ions

CIV only

With other ions

CIV only

Photoionisation model: CLOUDY

• Plane-parellel geometry• Solar-abundance pattern• Haardt-Madau QSO+Galaxies UV background

• For the CIV-only systems:• Schaye density law (2001)

For the metal systems: CIV, CII, SiIV, SiII, SiIII, OVI abundances

nH 1.23 x 10-14 NHI 2/3 T4

0.17 122/3 cm3

Improve measurement of [C/H]

[C/H] vs N(HI)

◊ : Dessauges-Zavadsky et al. (2003) : Songaila & Cowie (1996) : z ~ 3*

With other ions

CIV only

OVI: photoionisation failed

[C/H]med = -1.96

[C/H]med = -3.03

◊ : Dessauges-Zavadsky et al. (2003) : Songaila & Cowie (1996) : z ~ 3

With other ions

CIV only *

[C/H] vs z

OVI: photoionisation failed

Conclusions• 17 systems with N(HI) = 1015-17 cm-2 • Photoionisation model with QSO + Galaxies

reproduces the metal line ratios• For the 6 CIV-only systems: [C/H]med = -3.03 nHI ~ 10-3.5 cm-3

T ~ 4 x 104 K• For the 8 systems with additional ions the inferred

[C/H] is similar to that of sub-DLAs [C/H]med = -1.96 nHI ~ 10-2.5 cm-3

T ~ 4 x 104 K• At ~ 70 the measured [C/H] is consistent with [C/H] from Schaye at al. (2003)