Download Tae-Sun Kim

The metallicity of the high column
density Lya forest at 2 < z < 3.5
Tae-Sun Kim
Col: Bob Carswell
Institute of Astronomy
QSO absorption line systems: the Ly-a forest
highly ionised, low density absorption lines
QSO
Metal lines
CIV, SiIV, MgII, FeII
HI lines ( < 1017 cm-2)
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 d – 0.5)
(Schaye et al. 2003)
Metal enrichment of the IGM: Galaxy-IGM interplay
• Metallicity of systems N(HI) = 1015-19 cm-2
• Redshift dependence?
IGM
?
Pettini (2004)
Galaxies: spirals?
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
• VLT/UVES Archive data
• R ~ 45000, S/N ~ 30-50
• Voigt profile fitting with VPFIT:
QSOs
PKS1448-232
PKS0237-23
HE2217-2818
HE1122-1648
Q0329-385
Q0002-422
PKS2126-158
zem
2.219
2.223
2.406
2.412
2.435
2.767
3.280
NHI = 1015-17 cm-2
Forest redshifts
1.986-2.175
1.986-2.179
1.986-2.360
1.986-2.365
1.986-2.389
2.183-2.717
2.669-3.222
# of systems
1/0/1
1/0/1
3/0/3
2/0/2
2/0/2
6/3/6
12/3/5
Normalized flux
Normalized flux
N(HI) = 1015.10 cm-2
N(HI) = 1015.81 cm-2
N(CIV)/N(HI) vs N(HI)
With other ions
CIV only
*
◊ : Songaila & Cowie (1996) : z ~ 3
Photoionisation model: CLOUDY
• Plane-parellel geometry
• Solar-abundance pattern
• Haardt-Madau QSO+Galaxies UV background
• For the CIV-only systems:
• Schaye density law (2001)
nH ~ 1.23 x 10-14 NHI 2/3 T40.17 G122/3 cm-3
For the metal systems:
CIV, CII, SiIV, SiII, SiIII, OVI abundances
Improve measurement of [C/H]
[C/H] vs N(HI)
CIV only
[C/H]med = -3.03
OVI: photoionisation failed
With other ions
[C/H]med = -1.96
◊ : Dessauges-Zavadsky et al. (2003)
: Songaila & Cowie (1996) : z ~ 3
*
[C/H] vs z
OVI: photoionisation failed
With other ions
CIV only
◊ : Dessauges-Zavadsky et al. (2003)
: Songaila & Cowie (1996) : z ~ 3
*
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 d ~ 70 the measured [C/H] is
consistent with [C/H] from Schaye at al. (2003)