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The metallicity of the high column density Ly a forest at 2 < z < 3.5

The metallicity of the high column density Ly a 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.

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The metallicity of the high column density Ly a forest at 2 < z < 3.5

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  1. The metallicity of the high column densityLya forestat 2 < z < 3.5 Tae-Sun Kim Col: Bob Carswell Institute of Astronomy

  2. 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

  3. Observations: • ~90% of clouds with N(HI) > 1015cm-2are 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)

  4. 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

  5. Difficulties for N(HI) = 1015-17cm-2 zzzzzzzz • Saturation • Not many available ionic transitions • Sensitive to the UV background Most ionic lines are not saturated!!

  6. Observations and Data reduction • VLT/UVES Archive data • R~ 45000, S/N ~ 30-50 • Voigt profile fitting with VPFIT: NHI= 1015-17 cm-2 QSOs zem Forest redshifts # of systems PKS1448-232 2.219 1.986-2.175 1/0/1 PKS0237-23 2.223 1.986-2.179 1/0/1 HE2217-2818 2.406 1.986-2.360 3/0/3 HE1122-1648 2.412 1.986-2.365 2/0/2 Q0329-385 2.435 1.986-2.389 2/0/2 Q0002-422 2.767 2.183-2.717 6/3/6 PKS2126-158 3.280 2.669-3.222 12/3/5

  7. Normalized flux Normalized flux N(HI) = 1015.10 cm-2 N(HI) = 1015.81 cm-2

  8. With other ions With other ions CIV only CIV only N(CIV)/N(HI) vs N(HI) * ◊ :Songaila & Cowie (1996) : z ~ 3

  9. 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 T40.17 G122/3 cm-3 Improve measurement of [C/H]

  10. [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 *

  11. [C/H] vs z OVI: photoionisation failed With other ions ◊ :Dessauges-Zavadsky et al. (2003) : Songaila & Cowie (1996) : z ~ 3 * CIV only

  12. 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)

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