Lymanα forests and the evolution of the universe

Abstract

The Lya forest absorption lines in the spectra of quasars are interpreted as caused by the crossings of the light beam with the walls of a bubble structure (expanding with the Hubble flow only). Then, the typical separation between the absorption lines is proportional to the mean size of the bubbles. The variable factor is the expansion rate H [ z ] . T h e Friedmann regression analysis of the observed line separations determines the density parameter 0 0 and the normalized cosmological term A0 = A c 2 / 3 H i of the appropriate cosmological model: 00 = 0.014 f 0.002, Xo = 1:OSO f 0.006.Depending on the Hubble parameter this method reveals the values of the present mean matter density p~, o = 2.6 h Z . kg m-' and of the cosmological constant A = 3.77 hZ m-' (with h = Ho/(100 km/sMpc)). According to our analysis all models with A = 0 must be excluded. The curvature of space is positive. The curvature radius Ro is 3.3 times the Hubble radius ( c / H o ) . The age t o is 2.8 t,imes the Hubble age (IT;'). A A A subject classification: 161Recently, Hoell and Priester (1991b) ([HP91] hereafter) showed that the Lycr forest in quasar spectra can be understood as the result of a homogeneous bubble structure at least up to a redshift of z = 4.4 if the universe is represented by a Friedmann-Lemaitre model with an actual expansion rate Ho = 90 km/(s.Mpc) and an age of about 30. lo9 years. In the present paper we include data from further spectra, partly new, partly omitted in the first paper because of a too cautious estimation of their sensitivity. The analysis is now based on published spectra of 21 quasars with a total of 1320 Lya absorption lines and supports our former result (Liebscher, Priester, Hoell (1992) ([LPH92] hereafter)). The apparent increase in scatter is balanced by the increase in number. Hence, the estimated variance of the parameters does not change appreciably. The Friedmann regression analysis yields the values of the density parameter Q , and of the normalized cosmological term A 0 = A c 2 / 3 H i . The generalized density parameter Of = Qo + A0 turns out to exceed 1, i.e. the space is closed and the curvature index is k = $1.The method is based on the assumption that the bubble structure in the large scale distribution of matter, which is observed in our galactic neighbourhood up to a redshift of 0.05 (deLapparent et al. 1986) was at rest in comoving coordinates at least since the emission of the quasar light, and that the L y a forest in the quasar spectra is due to the cuts of the light beam through hydrogen filaments within the walls of the bubble structure. For a homogeneous and comoving bubble structure the size parameter X of the voids is independent of time. The mean spacing 2 between the absorption lines is measured as a function of the redshift z itself, and we replace the time t by the corresponding value of the redshift z . If we denote the typical bubble size in comoving radial distance x by X = Ax and the corresponding spacing of the redshifts by 2 = Az, we obtain I8 Astron. Nachr. 313 ...

Dark matter and background light

“…While there are a number of ways to account for this in ΛCDM models (e.g., by "tilting" the primordial spectrum), the data are fit most naturally by a "no-CDM" ΛBDM model with Ω cdm = 0, Ω m,0 = Ω bar and Ω Λ,0 ≈ 1 [142]. Models of this kind have been discussed for some time in connection with analyses of the Lyman-α forest of quasar absorption lines [50,143]. The Wmap data show a stronger second peak and are fit by both ΛCDM and ΛBDM-type models [144].…”

“…Fig. 23(a) shows the spectral intensity of background radiation from vacuum decay under our standard assumptions, including the relativistic definition (136) of vacuum luminosity and the values of Ω r,0 and β given by (143) and (144) respectively. Five groups of curves are shown, corresponding to values of x m between 3 × 10 −5 and the theoretical maximum of 0.25.…”

Wolfgang Priester: from the big bounce to the $\Lambda$-dominated universe

“…Their best-fit model, which came to be known as the "Bonn-Potsdam" or BN-P model, was characterized by a dark-energy density of Ω Λ,0 ≈ 1.08 and a total matter density of Ω M,0 ≈ 0.014, as measured in units of the critical density [88][89][90][91][92][93].…”

Nucleosynthesis in the Big Bang and in Stars

“…55. Here, it was reported that, even as early as the 1940's, Pontecorvo and Alvarez independently proposed that the neutrinos produced in the solar interior might be detectable on earth by neutrino capture in 37 Cl. This idea was revived by Fowler, Cameron, Davis, and Bahcall after it became clear that there was a good chance that 8 B solar neutrinos might be more intense than previously seemed likely.…”

“…Note, however, that this conclusion is not necessarily true if the cosmological constant , which is usually set to zero, has a finite value as recently proposed. (37) Although the standard model provides a consistent picture of the nuclear ashes of the early universe, this is not sufficient to establish the correctness of the model or its uniqueness. Thus it seems to be advisable to investigate alternative models in which one or even several of the assumptions made in the standard model are relaxed.…”