نتایج جستجو برای: intergalactic matter
تعداد نتایج: 216639 فیلتر نتایج به سال:
Stars and gas in galaxies, hot intracluster medium, and intergalactic photo-ionized gas make up at most half of the baryons that are expected to be present in the universe. The majority of baryons are still missing and are expected to be hidden in a web of warm-hot intergalactic medium. This matter was shock-heated during the collapse of density perturbations that led to the formation of the re...
We calculate the observable signatures of the rst generation of stars at high redshifts (5 < z < 10 3). We determine the cosmic star{formation history, using an extension of the Press{Schechter formalism for Cold Dark Matter (CDM) cosmologies, and calibrate the fraction of gas converted into stars so as to reproduce the C/H ratio observed in the intergalactic medium at z = 3. We nd that the Uni...
Observations from the Hopkins Ultraviolet Telescope and the Hubble Space Telescope have recently detected HeII absorption along the lines of sight to two high redshift quasars. We use cosmological simulations with gas dynamics to investigate HeII absorption in the cold dark matter (CDM) theory of structure formation. We consider two Ω = 1 CDM models with different normalizations and one open un...
We present the first results from a survey of the relative spatial distributions of galaxies, intergalactic neutral hydrogen, and intergalactic metals at high redshift. We obtained high-resolution spectra of 8 bright QSOs at 3.1 < z < 4.1 and spectroscopic redshifts for 431 Lyman-break galaxies (LBGs) at slightly lower redshifts. Comparing the locations of galaxies to the absorption lines in th...
The spectra of the first galaxies and quasars in the Universe should be strongly absorbed shortward of their rest-frame Lyα wavelength by neutral hydrogen (HI) in the intervening intergalactic medium. However, the Lyα line photons emitted by these sources are not eliminated but rather scatter until they redshift out of resonance and escape due to the Hubble expansion of the surrounding intergal...
High-resolution hydrodynamics simulations of the Lyα forest in cold dark matter dominated cosmologies appear to predict line widths that are substantially narrower than those observed. Here we point out that Compton heating of the intergalactic gas by the hard X–ray background (XRB), an effect neglected in all previous investigations, may resolve this discrepancy. The rate of gain in thermal en...
Context. Hydrodynamical simulations indicate that substantial fraction of baryons in the Universe remains in a diffuse component – Warm-Hot Intergalactic Medium (WHIM). Aims. To determine physical properties (spatial distribution, temperature and density) of WHIM. Methods. Spatial structure of the soft extended X-ray emission surrounding field galaxies is carefully investigated using the XMM-Ne...
We report the discovery of the optical afterglow (OA) of the long-duration gamma-ray burst GRB 030429, and present a comprehensive optical/near-infrared dataset used to probe the matter at different distance scales, i.e. in the burst environment, in the host galaxy and in an intervening absorber. A break in the afterglow light curve is seen approximately 1 day from the onset of the burst. The l...
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