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Rix, Samantha A.; Steidel, C.; Hunt, Matthew P.; Shapley, Alice E.; Adelberger, Kurt L.

doi:10.1023/a:1019500911063

Cited by 50 publications

(64 citation statements)

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“…Despite the difficulty, several accurate determinations have been made ͑Burles and Tytler, 1998aTytler, , 1998bO'Meara et al, 2001O'Meara et al, , 2006Pettini and Bowen, 2001;Levshakov et al, 2002;Kirkman et al, 2003;Crighton et al, 2004͒. The current best estimate for D/H is log 10 D/H=−4.55± 0.04 ͑O'Meara et al, 2006͒.…”

Section: Deuterium Absorption Systemsmentioning

confidence: 99%

The physics of the intergalactic medium

2009

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Intergalactic space is filled with a pervasive medium of ionized gas, the intergalactic medium ͑IGM͒. A residual neutral fraction is detected in the spectra of quasistellar objects at both low and high redshifts, revealing a highly fluctuating medium with temperatures characteristic of photoionized gas. The statistics of the fluctuations are well reproduced by numerical gravity-hydrodynamics simulations within the context of standard cosmological structure formation scenarios. Thus, the study of the IGM offers an opportunity to probe the nature of the primordial density fluctuations on scales unavailable to other methods. The simulations also suggest that the IGM is the dominant reservoir of baryons produced by the Big Bang, and so the principal source of the matter from which galaxies formed. The detection of metal systems within the IGM shows that it was enriched by evolved stars early in its history, demonstrating an intimate connection between galaxy formation and the IGM. A comprehensive review of the current understanding of the structure and physical properties of the IGM and its relation to galaxies is presented, concluding with comments on prospects for furthering the study of the IGM using future ground-based facilities and space-based experiments.

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Section: Deuterium Absorption Systemsmentioning

confidence: 99%

The physics of the intergalactic medium

2009

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“…Madau et al (1998) use a universal value of E(B−V ) = 0.1, Guiderdoni (1999) prefers E(B − V ) = 0.09 at z > 2. Generally, dust extinction seems to play a more important role at high redshifts (e.g., Pettini et al 1998). According to Madau et al (1998) the index varies as E(B − V ) = 0.011(1 + z) 2.2 .…”

Section: Interstellar Mediummentioning

confidence: 99%

Implications of cosmological gamma-ray absorption

Kneiske

Mannheim

Hartmann

2002

A&A

153

222

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Abstract. Gamma-ray absorption due to γγ-pair creation on cosmological scales depends on the line-of-sight integral of the evolving density of low-energy photons in the Universe, i.e. on the history of the diffuse, isotropic radiation field. Here we present and discuss a semi-empirical model for this metagalactic radiation field based on stellar light produced and reprocessed in evolving galaxies. With a minimum of parameters and assumptions, the present-day background intensity is obtained from the far-IR to the ultraviolet band. Predicted model intensities are independent of cosmological parameters, since we require that the comoving emissivity, as a function of redshift, agrees with observed values obtained from deep galaxy surveys. The far-infrared background at present predicted from optical galaxy surveys falls short in explaining the observed one, and we show that this deficit can be removed by taking into account (ultra)luminous infrared galaxies with a seperate star formation rate. The accuracy and reliability of the model, out to redshifts of z ∼ 5, allow a realistic estimate of the attenuation length of GeV-to-TeV gamma-rays and its uncertainty, which will be the focus of a subsequent paper.

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“…These winds have primarily been seen close to the star-forming regions they originate in (McCarthy et al 1987;Franx et al 1997;Pettini et al 2001Pettini et al , 2002Heckman 2002), but based on their large power and analogies with lowredshift superwinds, it has been proposed that they may be able to escape galaxies and profoundly affect the properties of the IGM, blowing bubbles of highly ionized, metal-rich gas out to distances of more than half a Mpc (comoving; Adelberger et al 2003;Cen et al 2004). The first instances of individual superwinds actually leaving high-redshift galaxies may have been seen in Mg ii (Bond et al 2001a(Bond et al , 2001b and O vi (Simcoe et al 2002) absorption systems.…”

Section: Limits On Other Sources Of Motion In the Intergalactic Mediummentioning

confidence: 99%

Expansion and Collapse in the Cosmic Web

Rauch

Becker

Viel

et al. 2005

ApJ

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We study the kinematics of the gaseous cosmic web at high redshift using Ly forest absorption in multiple QSO sight lines. Observations of the projected velocity shifts between Ly absorbers common to the lines of sight to a gravitationally lensed QSO and three more widely separated QSO pairs are used to directly measure the expansion of the cosmic web in units of the Hubble velocity, as a function of redshift and spatial scale. The lines of sight used span a redshift range from about 2 to 4.5 and represent transverse scales from the subkiloparsec range to about 300 h À1 70 physical kpc. Using a simple analytic model and a cosmological hydrodynamic simulation, we constrain the underlying three-dimensional distribution of expansion velocities from the observed line-of-sight distribution of velocity shear across the plane of the sky. The shape of the shear distribution and its width (14.9 km s À1 rms for a physical transverse separation of 61 h À1 70 kpc at z ¼ 2, 30.0 km s À1 for 261 h À1 70 kpc at z ¼ 3:6) are found to be in good agreement with the IGM undergoing large-scale motions dominated by the Hubble flow, making this one of the most direct observations possible of the expansion of the universe. However, modeling the Ly clouds with a simple ''expanding pancake'' model, the average expansion velocity of the gaseous structures causing the Ly forest in the lower redshift (z $ 2) smaller separation (61 kpc) sample appears about 20% lower than the local Hubble expansion velocity.In order to understand the observed velocity distribution further we investigated the statistical distribution of expansion velocities in cosmological Ly forest simulations. The mean expansion velocity in the (z $ 2, separation $ 60 kpc) simulation is indeed somewhat smaller than the Hubble velocity, as found in the real data. We interpret this finding as tentative evidence for some Ly forest clouds breaking away from the Hubble flow and undergoing the early stages of gravitational collapse. However, the distribution of velocities is highly skewed, and the majority of Ly forest clouds at all redshifts from 2 to 3.8 expand with super-Hubble velocities, typically about 5%-20% faster than the Hubble flow. This behavior is explained if most Ly forest clouds in the column density range typically detectable are expanding filaments that stretch and drain into more massive nodes. The significant difference seen in the velocity distributions between the high-and low-redshift samples may conceivably reflect actual peculiar deceleration, the differences in spatial scale, or our selecting higher densities at lower redshift for a given detection threshold for Ly forest lines.We also investigate the alternative possibility that the velocity structure of the general Ly forest could have an entirely different, local origin, as expected if the Ly forest were produced or at least significantly modified by galactic feedback, e.g., winds from star-forming galaxies at high redshift. However, we find no evidence that the observed distribution of veloc...

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Cited by 50 publications

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The physics of the intergalactic medium

The physics of the intergalactic medium

Implications of cosmological gamma-ray absorption

Expansion and Collapse in the Cosmic Web

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