Related papers: Ly alpha Cloud Size Evolution and Shape from QSO G…
We describe a robust Bayesian statistical method for determining Lyman alpha forest cloud sizes in spherical and in thin disk geometries, using absorption in adjacent sightlines toward closely separated QSO pairs and groups, apply this…
We present a high signal-to-noise high resolution spectrum of the radio-quiet QSO HS1700+6416 (z = 2.72). Analysis of the absorption line systems with metals yields the following results. (1) The dense cluster of C IV doublets at 2.432 <…
We combine a semi-analytical model of galaxy formation with a very large simulation which follows the growth of large scale structure in a LambdaCDM universe to predict the clustering of Ly-alpha emitters. We find that the clustering…
We present results from a survey of the Lyman alpha forest at 2.15<z<3.26 toward ten QSOs concentrated within a 1 degree field. We find correlations of the Lyman alpha absorption line wavelengths between different lines-of-sight over the…
The spatial distribution of the Ly$\alpha$ forest is studied using new HST data for the quasar pair Q~1026--0045 A and B at $z_{em}$ = 1.438 and 1.520 respectively. The angular separation is 36 arcsec and corresponds to transverse linear…
We outline the physical picture of the high-redshift Ly-alpha forest that has emerged from cosmological simulations, describe statistical characteristics of the forest that can be used to test theories of structure formation, present a…
The main observed properties of Ly-$\alpha$ absorbers are investigated on the basis of theoretical model of formation and evolution of DM structure elements. This model is generally consistent with simulations of absorbers formation and…
We report the detection of a significant clustering signal on scales $\Delta v < 300$ km/s, for a sample of 71 C IV absorbers. This result confirms previous findings and, together with data at lower column density, it points to a trend of…
I review results obtained from studies of the high-redshift Lyman alpha forest, and present new results from HST/STIS spectra of low-redshift quasars in comparison with cosmological hydrodynamic simulations. The evolution of the Lyman alpha…
To study the nature of low z Lya absorbers in the spectra of QSOs, we have obtained high signal-to-noise UV spectra of H 1821+643 (z = 0.297) and PG 1116+215 (z = 0.177) with the GHRS on the HST. The spectra have minimum S/N of 70-100 and 3…
The properties of the Lyman-$\alpha$ absorptions observed in the spectra of QSOs are reviewed: the distribution of column densities and Doppler widths, the redshift evolution, the ``inverse effect'', the clustering. By interpreting the…
We study the kinematics of the gaseous cosmic web at high redshift with Lyman alpha forest absorption in multiple QSO sightlines. Using a simple analytic model and a cosmological hydrodynamic simulation we constrain the underlying…
We examine the Ly-alpha absorber population at z<0.3 detected in spectra of the QSOs PG0953+415 and H1821+643 taken with the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope. We compare their statistical properties to…
We present a study of the Ly\alpha forest at z<0.4 from which we conclude that at least 20% of the total baryons in the universe are located in the highly-ionized gas traced by broad Ly\alpha absorbers. The cool photoionized low-z…
We describe recent discoveries of low column density [N(HI) < 10^14.5 cm^-2] H I Ly-alpha absorbers made with the Hubble Space Telescope (HST), which have allowed us a first look at gas in local intergalactic space between us and the "Great…
In Paper I of this series (astro-ph/9911117) we described observations of 15 extragalactic targets taken with the Hubble Space Telescope GHRS/G160M grating for studies of the low-z Lya forest. We reported the detection of 110 Lya absorbers…
Using high resolution (R ~ 45000), high S/N (20-50) VLT/UVES observations covering the Lyman-alpha forest at 1.5 < z < 2.4 combined with similar observations at z > 2.4 from the literature, we have presented the redshift evolution of the…
We study the galaxy number density (smoothed on a 5h^{-1} Mpc scale) around 18 low-redshift Lyman-alpha absorbers previously observed with HST. The absorbers lie in the foregrounds of Mrk 335, Mrk 421, Mrk 501, I Zw 1, and 3C 273, all…
This study analyzes the sizes, shapes and correlations of $\lya$ clouds produced by a hydrodynamic simulation of a spatially flat CDM universe with a non-zero cosmological constant ($\Omega_0=0.4$, $\Lambda_0=0.6$, $\sigma_8 =0.79$), over…
We present the highest quality Lyman Alpha forest spectra published to date, from the QSO HS 1946+7658. The distribution of H I column densities is a power law of slope -1.5 from Log N = 12.1 - 14. This power law can extend to N = 0,…