Investigation And Analysis Of Doppler Redshifts Of Quasars

We summarize the observational and theoretical studies of quasars, and present the results of our studies on the Doppler redshifts of quasars.It is particularly important to study the absorption lines of quasar. First, studies on intrinsic absorption lines can help us to understand the structure of quasars and the physical processes arising from them. On the other hand, quasars are one of the most distant objects observed so far, and studies on absorption lines arising from inserted objects enable us to understand the matter and motion within vast space-time range, the galactic formation and evolution and large-scale structure of the universe.The absorption lines of quasars are very complicated. Most of the redshifts of the absorption systems are smaller than the corresponding redshift of quasar, i.e. Z_absem. It has been generally known that absorption systems with z_absem are arisen from inserted objects whose distances are smaller than the corresponding quasars, and absorption systems with Z_abs≈Z_em are intrinsic ones, generally due to the relative motions of the absorbers and the quasars. The case of Z_abs>Z_em is seldom studied. We suspect that the phenomenon of absorption redshifts greater than their corresponding emission redshifts might be due to the fact that some absorbers are close to and move towards the quasars, and then the absorption redshifts contain their cosmological redshifts and Doppler redshifts. We extracted 256 absorption systems with absorption redshifts greater than the emission redshifts (Z_abs>Z_em). These absorption systems contain 123 quasars. We calculated their Doppler redshifts using Z_Dopp=(z_abs-Z_em)/ (1+Z_em) and then analyzed the data and found that there is a bi-peak structure in the distribution of Doppler redshifts, where one peak is located at Z_Dopp=0.0 and the other one at Z_Dopp=0.01. The second peak corresponds to a Doppler velocity of 3000 km s-1. We suspect that those having large Doppler redshift might be more massive. Massive quasars would possess larger gravity and therefore could produce larger Doppler velocities. Since they are more massive, they might be brighter. We divided quasars available in a quasar catalogue into three groups according to their Doppler redshifts and then performed a K-S test to the distributions of luminosities of the three groups of quasars. The results favor our supposal.Our main efforts and results are as follows. We analyzed the distribution of Doppler redshifts of quasars with z_abs>Z_em and found a bi-peak structure in the distribution. Analyzing the second peak reveals that there is a sub-set of quasars, which has the following characteristics: 1) Their Doppler redshifts are greater than 0.0088; 2) They are found to be generally brighter than others; 3) The Doppler velocities of the absorbers of these quasars are concentrated at～3000 km s^-1. We presented an interpretation to the phenomenon of larger Doppler redshifts of quasars with Z_abs>Z_em: absorption systems with large values of Z_abs-Z_em are due to relative motions and the absorbers are falling towards the central region of quasars with a velocity of～3000 km s^-1.In addition, we discussed the distributions of quasar absorbers with all absorption redshifts in space. We calculated the Doppler redshifts (the extended Doppler redshifts defined in Qin et al. 2004) of six kinds of absorbers, MgⅡ, FeⅡ, CⅣ, HI, LLS and DLA, available in a large absorption lines sample. From the distributions of their Doppler redshifts, we find that MgⅡand FeⅡabsorbers are probably homogeneous distributions in the universe. The distributions of Lyman limits in the universe may be the same as those of quasars. This agrees with the evolution relationship between the number of absorbers per unit redshift and redshift for Lyman limits. H I absorbers are likely having a constant distance to the quasars. It deserves a further investigation.The issue of whether there is an evolution relationship between Doppler redshifts of quasars and cosmological redshifts was also discussed. A linear correlation analysis between 256 positive Doppler redshifts and their cosmological redshifts shows that there is a weak correlation between Doppler redshifts and their cosmological redshifts. The evolution of Doppler redshifts suggests that the relative motions between the close absorbers and the corresponding quasars might be more violent at the early epoch of the universe than at the late epoch. A detailed analysis on this issue is included in our plan.