|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)
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
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.
理論的研究においては、CDMモデルに基づいた3次元宇宙論的数値流体計算シュミレーションを銀河形成、超新星爆発、銀河風の要素を取り入れて行い、大規模構造形成と銀河間物質の金属汚染の進化を調べた。主な結論は、(1)金属ガス分布は極めて非一様で銀河の形成されるフィラメント状の高密度領域に沿っており、パッチ状である。(2)低密度領域には金属汚染が発生しない。(3)O VIなどはLy-α線と同程度のbを持つことが予測されたので、LAFに埋もれてこれまで検出できないと考えられていた金属吸収線の測定を見直すべきである。(4)本研究においては上記観測結果(1)で示された低密度領域サイズは、シュミレーションの空間ボックスサイズ20h^<-1>Mpcのためにその存在の説明はできなかった。今後の課題である。 Less