The Lyα forest around high-redshift galaxies

Bruscoli, M.; Ferrara, Andrea; Marri, S.; Schneider, Raffaella; Maselli, Antonella; Rollinde, Emmanuel; Aracil, B.

doi:10.1046/j.1365-8711.2003.06784.x

Cited by 39 publications

(65 citation statements)

References 23 publications

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“…The bubbles produced by galactic winds are very clearly seen in the temperature structure. Similar wind structures have been found in other simulations using the smoothed particle hydrodynamics (SPH) technique (e.g., Theuns et al 2002;Bruscoli et al 2003). The size of the hot bubbles clearly increases with the strength of the winds.…”

Section: Physical Impact Of the Winds On The Igm And The Ly Forestsupporting

confidence: 83%

“…Simple wind models in which LBGs were associated with massive galaxies at high redshift (Croft et al 2002;Kollmeier et al 2003aKollmeier et al , 2003bDesjacques et al 2004) have shown that gas must be affected at unrealistically large distances from galaxies to result in increased Ly transmission. More sophisticated wind model prescriptions (Croft et al 2002;Bruscoli et al 2003) do not match the observations of Adelberger et al (2003) either. Photoionization by a massive galaxy itself does not produce an intensity of ionizing radiation that is large compared to the cosmic background (Croft et al 2002;Kollmeier et al 2003a).…”

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confidence: 89%

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Galactic Wind Effects on the Lyα Absorption in the Vicinity of Galaxies

Kollmeier

Miralda-Escudé

Cen

et al. 2006

ApJ

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We present predictions of Ly forest-galaxy correlations at z ¼ 3 from Eulerian simulations that include the effects of galactic winds, driven primarily by supernova explosions. Galactic winds produce expanding bubbles of shock-heated gas within $0.5 comoving h À1 Mpc of luminous galaxies in the simulation, which have space density similar to that of observed Lyman break galaxies (LBGs). However, most of the low-density intergalactic gas that determines the observed properties of the Ly forest is unaffected by winds. The impact of winds on the Ly optical depth near galaxies is less dramatic than their impact on gas temperature, because winds heat only a small fraction of the gas present in the turnaround regions surrounding galaxies. Hence, Ly absorption from gas outside the wind bubbles is spread out over the same velocity range occupied by the wind-heated gas. In general, Ly absorption is expected to be stronger than average near galaxies because of the high gas density. Winds result in a modest reduction of this expected increase of Ly absorption. Our predictions can be compared to future observations to detect the wind effects and infer their strength, although with the caveat that the results are still dependent on the correspondence of simulated galaxies and observed LBGs. We find that wind effects in our simulations are not strong enough to reproduce the high Ly transmission within 0.5 h À1 Mpc comoving of galaxies that has been suggested by recent observations; powerful galactic explosions or ejecta with hyper-escape velocities would be required, but these are unlikely to be produced by ordinary star formation and supernovae alone. Subject headingg s: galaxies: high-redshift -intergalactic medium -large-scale structure of universequasars: absorption lines

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Section: Physical Impact Of the Winds On The Igm And The Ly Forestsupporting

confidence: 83%

mentioning

confidence: 89%

Galactic Wind Effects on the Lyα Absorption in the Vicinity of Galaxies

Kollmeier

Miralda-Escudé

Cen

et al. 2006

ApJ

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“…Kollmeier et al (2006) found that the gas in the IGM is unaffected by the presence of winds and has only a small impact on the optical depth close to LBGs. Theuns et al (2002) and Bruscoli et al (2003) likewise found that the winds preferentially expanded into the voids, leaving the hydrogen filaments intact. It therefore seems likely that we are correctly modeling the H i around the LBGs.…”

Section: Intergalactic Metalsmentioning

confidence: 89%

The Environmental Impact of Lyman Break Galaxies

Tasker

Bryan

2006

ApJ

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We perform cosmological simulations of galaxies forming at using the hydrodynamics grid code, Enzo. z p 3 By selecting the largest galaxies in the volume to correspond to Lyman break galaxies, we construct observational spectra of the H i flux distribution around these objects, as well as column densities of C iv and O vi throughout a refined region. We successfully reproduce the most recent observations of the mean H i flux in the close vicinity of Lyman break galaxies but see no evidence for the proximity effect in earlier observations. While our galaxies do return metals to the intergalactic medium, their quantity and volume appear to be somewhat less than observed. We conclude either that we do not adequately resolve galactic winds or that at least some of the intergalactic metal enrichment is by early epoch objects whose mass is smaller than our minimum resolved halo mass.

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“…On large scales -cubes of comoving size ∼ 13h −1 Mpc -ASSP find a clear correlation of galaxy overdensity with Lyα flux decrement, the expected signature of galaxy formation in overdense environments [37,39]. However, the observed Lyα decrement decreases within ∆ r ≈ 1h −1 Mpc of LBGs (comoving, redshift-space separation), where the simulations predict that absorption should be strongest [38,39,40]. Figure 5 illustrates this conflict.…”

Section: The Galaxy Proximity Effectmentioning

confidence: 97%

“…Only the mass-scaled and R w = 1.5h −1 Mpc models come close to matching the ASSP data. Winds that fully ionize or perfectly entrain gas to such large distances are not a natural outcome of hydrodynamic simulations with stellar feedback [43,40], and even reaching 1.5h −1 Mpc in ∼ 1 Gyr requires a sustained propagation speed ∼ 600 km s −1 . Given the challenges facing the wind explanation, it is worth considering the alternative possibility that extended Lyα emission from the target galaxies is "filling in" the corresponding region of the absorption spectrum.…”

Section: The Galaxy Proximity Effectmentioning

confidence: 99%

The Lyman-α Forest as a Cosmological Tool

Weinberg¹,

Davé²,

Katz³

et al. 2003

AIP Conference Proceedings

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Abstract. We review recent developments in the theory of the Lyα forest and their implications for the role of the forest as a test of cosmological models. Simulations predict a relatively tight correlation between the local Lyα optical depth and the local gas or dark matter density. Statistical properties of the transmitted flux can constrain the amplitude and shape of the matter power spectrum at high redshift, test the assumption of Gaussian initial conditions, and probe the evolution of dark energy by measuring the Hubble parameter H(z). Simulations predict increased Lyα absorption in the vicinity of galaxies, but observations show a Lyα deficit within ∆ r ∼ 0.5h −1 Mpc (comoving). We investigate idealized models of "winds" and find that they must eliminate neutral hydrogen out to comoving radii ∼ 1.5h −1 Mpc to marginally explain the data. Winds of this magnitude suppress the flux power spectrum by ∼ 0.1 dex but have little effect on the distribution function or threshold crossing frequency. In light of the stringent demands on winds, we consider the alternative possibility that extended Lyα emission from target galaxies replaces absorbed flux, but we conclude that this explanation is unlikely. Taking full advantage of the data coming from large telescopes and from the Sloan Digital Sky Survey will require more complete understanding of the galaxy proximity effect, careful attention to continuum determination, and more accurate numerical predictions, with the goal of reaching 5 − 10% precision on key cosmological quantities. PHYSICS OF THE FORESTThe 1990s saw four epochal advances in our understanding of the Lyα forest. Spectra of quasar pairs showed coherence over scales of a hundred kpc and more, implying large sizes and thus low densities for the absorbing structures [1,2,3,4]. Keck HIRES spectra of unprecedented resolution and signal-to-noise demonstrated the ubiquity of weakly fluctuating Lyα absorption in the high redshift universe [5], and they revealed the presence of metal lines associated with low column density hydrogen absorbers [6,7]. Finally, and most directly relevant to this review, a combination of numerical simulations and related analytic models led to a compelling new physical picture of Lyα forest absorption [8,9,10,11,12,13,14,15].The basic numerical result is simple to summarize: given a cosmological scenario motivated by independent observations, 3-d simulations that incorporate gravity, gas dynamics, and photoionization by the UV background produce something very much like the observed Lyα forest, an outcome that requires no ad hoc adjustments to the model. The top three rows of Figure 1 illustrate this point, showing, respectively, the observed Lyα forest of the z = 3.62 quasar Q1422+231, expanded views of four selected regions of this spectrum, and simulated spectra of the same length along four randomly selected lines of sight through a cosmological simulation. The simulation uses smoothed

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The Lyα forest around high-redshift galaxies

Cited by 39 publications

References 23 publications

Galactic Wind Effects on the Lyα Absorption in the Vicinity of Galaxies

Galactic Wind Effects on the Lyα Absorption in the Vicinity of Galaxies

The Environmental Impact of Lyman Break Galaxies

The Lyman-α Forest as a Cosmological Tool

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