Intergalactic HeII absorption towards QSO 1157+3143

Reimers, D.; Fechner, C.; Hagen, H. J.; Jakobsen, P.; Tytler, David; Kirkman, David

doi:10.1051/0004-6361:20053365

Cited by 48 publications

(74 citation statements)

References 24 publications

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“…Figure 14 plots τ eff,He ii from our simulations and from the most constraining observations, where τ eff,He ii is defined as minus the log of the He ii Lyα forest transmission. The square markers are from observations of quasars HS1700+6416 (Fechner et al 2006), HS1157+3143 (Reimers et al 2005), PKS1935−692 (Anderson et al 1999), Q0302−003 (Heap et al 2000), and SDSSJ2346−0016 . The vertical error bars on these measurements are just statistical, and the horizontal error bars signify the redshift range over which each of the values were estimated.…”

Section: Mean He II Lyα Forest Transmissionmentioning

confidence: 99%

He II REIONIZATION AND ITS EFFECT ON THE INTERGALACTIC MEDIUM

McQuinn¹,

Lidz²,

Zaldarriaga³

et al. 2009

ApJ

260

465

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Observations of the intergalactic medium (IGM) suggest that quasars reionize He ii in the IGM at z ≈ 3. We have run a set of 190 and 430 comoving Mpc simulations of He ii being reionized by quasars to develop an understanding of the nature of He ii reionization and its potential impact on observables. We find that He ii reionization heats regions in the IGM by as much as 25,000 K above the temperature that is expected otherwise, with the volume-averaged temperature increasing by ∼ 12,000 K and with large temperature fluctuations on ∼ 50 Mpc scales. Much of this heating occurs far from quasars by photons with long mean free path. We find a temperature-density equation of state of γ − 1 ≈ 0.3 during He ii reionization, but with a wide dispersion in this relation having σ T ∼ 10 4 K. He ii reionization by the observed population of quasars cannot produce an inverted relation (γ − 1 < 0). Our simulations are consistent with the observed evolution in the mean transmission of the He ii Lyα forest. We argue that the heat input from He ii reionization is unable to cause the observed depression at z ≈ 3.2 in the H i Lyα forest opacity as has been suggested. We investigate how uncertainties in the properties of QSOs and of He ii Lyman limit systems influence our predictions.

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Section: Mean He II Lyα Forest Transmissionmentioning

confidence: 99%

He II REIONIZATION AND ITS EFFECT ON THE INTERGALACTIC MEDIUM

McQuinn¹,

Lidz²,

Zaldarriaga³

et al. 2009

ApJ

260

465

View full text Add to dashboard Cite

show abstract

“…While the detection of a high He II Ly-␣ optical depth was expected, the wide range in fluctuations in came as a surprise. Some of the systems indicate values as large as Ͼ 1000 at z Շ 3 based on follow-up optical observations of the H I Ly-␣ systems corresponding to the He II systems detected ͑Zheng, Reimers et al, 2005;Fechner et al, 2006͒. Combining N He II measurements from FUSE observations over the redshift range 2.30Ͻ z Ͻ 2.75 with measurements of N H I for the corresponding H I systems using Keck observation, Fechner et al ͑2006͒ obtained a very broad distribution for , as shown in Fig. 11.…”

Section: Constraints From Helium Ionizationmentioning

confidence: 99%

“…The measured values are well described by the model, except for a small tail at log 10 Ӎ 2.6. These values may be produced by patches of only partially ionized helium, as would remain during the epoch of He II reionization before its completion ͑Zheng, Reimers et al, 2005͒. Alternatively, they may result from local H I-ionizing sources reducing the H I column density, but not He II.…”

Section: Constraints From Helium Ionizationmentioning

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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“…As the reionization of the IGM is a gradual process, it is yet unclear when it started from a virtually neutral state. Indirect observational evidence (Theuns et al 2002;Zheng et al 2004b;Reimers et al 2005) suggests that the reionization of singly ionized helium started around z ' 3:4.…”

Section: Introductionmentioning

confidence: 99%

Intergalactic HeiiAbsorption in the Spectra of Quasars at Redshifts 3.5 and 3.8, Observed with theHSTACS Prism

Zheng

Meiksin

Pifko

et al. 2008

Astrophysical Journal

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We present the UV spectra of two quasars obtained with the Hubble Space Telescope Advanced Camera for Surveys (HST ACS) prism (R $ 100). One quasar, at redshift z ¼ 3:5, shows an absorption edge consistent either with nearly fully ionized helium with an intergalactic He ii Ly optical depth at 304 8 of 304 > 3:1 (90% confidence), or a He iii region with edge 5.4 Mpc from the QSO. The spectrum of the second quasar, at z ¼ 3:8, has a broad absorption profile extending across the He ii emission line of the quasar consistent with a damped absorption profile from an intervening He ii system at z ' 3:7 with a column density of approximately 10 22 cm À2 . In this case, the extremely high He ii column density and absence of strong H i absorption suggests that the radiation field is quite weak at 4 ryd. The combined He ii and H i signatures are consistent with photoionization by a compact (1Y100 pc) star-forming region located approximately 10 Mpc from the quasar.

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Intergalactic HeII absorption towards QSO 1157+3143

Cited by 48 publications

References 24 publications

He II REIONIZATION AND ITS EFFECT ON THE INTERGALACTIC MEDIUM

He II REIONIZATION AND ITS EFFECT ON THE INTERGALACTIC MEDIUM

The physics of the intergalactic medium

Intergalactic HeiiAbsorption in the Spectra of Quasars at Redshifts 3.5 and 3.8, Observed with theHSTACS Prism

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