| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2000: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1999: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1998: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
As for the observational study, the high dispersion spectra of the triplet QSO system (KP 76, 77, 78) obtained with Keck HIRES were analyzed. W-e measured values of redshift (z), column density (N (H) or N (metal)), and Doppler parameter (b) of Ly-α and metallic absorption lines in each Ly-α forest using the VPFIT code. The total numbers of measured Ly-α line are 153, 263, and 215 in KP76, 77, and 78, respectively. Among them, metallic line systems associate with 8, 8, and 13 Ly-α lines, respectively. Based on these measurements, we obtained the following main results : (1) Inspecting N (H) vs. z relation, the low-density regions with logN (H)<14 are found to exist at z=2.08 and 2.38, of which size along line of sight are 11-17 h^<-1> Mpc. Also the low-density region at z=2.50 is suggested. These sizes are not explained by the simulations based on CDM model described below. (2) The number density per unit z (dn/dz) shows a trend of strong evolution for log N (H)>14, while that of weak
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evolution for log N (H)=13-14. (3) The Log N (H) of Ly-α lines with metallic line systems is found to be larger than 14 in all cases. (4) The Ly-α lines with b>150 km/s are detected, which is consistent with theoretical simulations. At present we are preparing for the paper of these results.
As for theoretical studies, we investigated the formation of large-scale structures and evolution of metal pollution in intergalactic medium based on the 3-dimensional cosmological numerical simulations for CDM models, which are calculated by taking account of effects of galaxy formation, supernova explosion, and galactic wind. The main results are : (1) The distribution of metallic gas is found to be very inhomogeneous and exist along the high-density regions of filamentary structure, in which galaxy is formed. (2) The metallic pollution does not occur in low-density regions. (3) O VI lines show a broad feature like Ly-α lines, so it is worth trying to detect O VI lines in Ly-α forest. (4) The simulation prediction of the observed low-density regions will be made by a future study. Less
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