The Fluctuating Intergalactic Radiation Field at Redshifts<i>z</i>= 2.3–2.9 from He<scp>ii</scp>and H<scp>i</scp>Absorption toward HE 2347−4342

Shull, J. M.; Tumlinson, Jason; Giroux, Mark L.; Kriss, G. A.; Reimers, D.

doi:10.1086/379924

Cited by 103 publications

(270 citation statements)

References 33 publications

Supporting

Mentioning

231

Contrasting

Order By: Relevance

“…The SED differs significantly from system to system, so that we can conclude that the ionization field fluctuates at the redshift scale of at least Δ z ∼ 0.004. This is comparable with Δ z 0.01 revealed from joint observations of He ii and H i Ly-α forest at 2.0 < z < 2.9 (Shull et al 2004(Shull et al , 2010. Figure 16 shows η ≡ N(He ii)/N(H i), the parameter used in the forest studies to probe fluctuations of the ionizing background with z.…”

Section: Discussionsupporting

confidence: 73%

Fluctuations of the intergalactic ionization field at redshiftz~ 2

Agafonova

Levshakov

Reimers

et al. 2013

A&A

View full text Add to dashboard Cite

Aims. To probe the spectral energy distribution (SED) of the ionizing background radiation at z 2 and to specify the sources contributing to the intergalactic radiation field. Methods. The spectrum of a bright quasar HS 1103+6416 (z em = 2.19) contains five successive metal-line absorption systems at z abs = 1.1923, 1.7193, 1.8873, 1.8916, and 1.9410. The systems are optically thin and reveal multiple lines of different metal ions with the ionization potentials lying in the extreme ultraviolet (EUV) range (∼1 Ryd to ∼0.2 keV). For each system, the EUV SED of the underlying ionization field is reconstructed by means of a special technique developed for solving the inverse problem in spectroscopy.For the z abs = 1.8916 system, the analysis also involves the He i resonance lines of the Lyman series and the He i λ504 Å continuum, which are seen for the first time in any cosmic object except the Sun. Results. From one system to another, the SED of the ionizing continuum changes significantly, indicating that the intergalactic ionization field at z 2 fluctuates at the scale of at least Δ z ∼ 0.004. This is consistent with Δ z 0.01 estimated from He ii and H i Lyman-α forest measurements between the redshifts 2 and 3. A radiation intensity break by approximately an order of magnitude at E = 4 Ryd in SEDs restored for the z abs = 1.1923, 1.8873, 1.8916, and 1.9410 systems points to quasars as the main sources of the ionizing radiation. The SED variability is mostly caused by a small number of objects contributing at any given redshift to the ionizing background; at scales Δ z 0.05, the influence of local radiation sources becomes significant. A remarkable SED restored for the z abs = 1.7193 system, with a sharp break shifted to E ∼ 3.5 Ryd and a subsequent intensity decrease by ∼1.5 dex, indicates a source with comparable inputs of both hard (active galactic nuclei, AGN) and soft (stellar) radiation components. Such a continuum can be emitted by (ultra) luminous infrared galaxies, many of which reveal both a strong AGN activity and intense star formation in the circumnuclear regions.

show abstract

Section: Discussionsupporting

confidence: 73%

Fluctuations of the intergalactic ionization field at redshiftz~ 2

Agafonova

Levshakov

Reimers

et al. 2013

A&A

View full text Add to dashboard Cite

show abstract

“…The best sample so far surrounds the line of sight to HE 2347-4342, whose He ii forest has been extensively studied Shull et al 2004;Fechner & Reimers 2007;Shull et al 2010). Worseck et al (2007) searched for nearby quasars with L min 1-2 × 10 11 L and a maximum impact parameter ∼12 comoving Mpc.…”

Section: Comparison To Existing Observationsmentioning

confidence: 99%

CONSTRAINTS ON QUASAR LIFETIMES AND BEAMING FROM THE He II Lyα FOREST

Furlanetto

Lidz

2011

ApJ

View full text Add to dashboard Cite

We show that comparisons of He ii Lyα forest lines of sight to nearby quasar populations can strongly constrain the lifetimes and emission geometry of quasars. By comparing the He ii and H i Lyα forests along a particular line of sight, one can trace fluctuations in the hardness of the radiation field (which are driven by fluctuations in the He ii ionization rate). Because this high-energy background is highly variable-thanks to the rarity of the bright quasars that dominate it and the relatively short attenuation lengths of these photons-it is straightforward to associate features in the radiation field with their source quasars. Here we quantify how finite lifetimes and beamed emission geometries affect these expectations. Finite lifetimes induce a time delay that displaces the observed radiation peak relative to the quasar. For beamed emission, geometry dictates that sources invisible to the observer can still create a peak in the radiation field. We show that both these models produce substantial populations of "bare" peaks (without an associated quasar) for reasonable parameter values (lifetimes ∼10 6 -10 8 yr and beaming angles 90 • ). A comparison to existing quasar surveys along two He ii Lyα forest lines of sight rules out isotropic emission and infinite lifetime at high confidence; they can be accommodated either by moderate beaming or lifetimes ∼10 7 -10 8 yr. We also show that the distribution of radial displacements between peaks and their quasars can unambiguously distinguish these two models, although larger statistical samples are needed.

show abstract

“…Three different analysis methods have been applied to the observations of the He  Lyα forest so far: line profile fitting (Kriss et al 2001;Zheng et al 2004;Fechner et al 2006a), an apparent optical depth method (Shull et al 2004;Fechner et al 2006a) and spectrum fitting (Fechner & Reimers 2007). The latter fits the high-quality optical H  spectrum directly to the He  data, and allows to estimate the length scales of η variations.…”

Section: Methodsmentioning

confidence: 99%

“…We select spectral ranges with a size of ∼5 Å, corresponding to ∆z ∼ 0.016. Scales of variation of the UV background in this order of magnitude have been estimated by Fechner & Reimers (2007), whereas Shull et al (2004) and Bolton et al (2006) find much smaller scales in the range ∆z ∼ 0.001. Realistically, we do not expect to be able to derive robust constraints on the parameters of the temperature-density relation.…”

Section: Application To Observationsmentioning

confidence: 98%

See 1 more Smart Citation

The HeII Lyman alpha forest and the thermal state of the IGM

Fechner

Reimers

2006

A&A

View full text Add to dashboard Cite

Aims. Recent analyses of the intergalactic UV background by means of the He  Lyα forest assume that He  and H  absorption features have the same line widths. We omit this assumption to investigate possible effects of thermal line broadening on the inferred He /H  ratio η and to explore the potential of intergalactic He  observations to constrain the thermal state of the intergalactic medium. Methods. Deriving a simple relation between the column density and the temperature of an absorber based on the temperature-density relation T = T 0 (1 + δ) γ−1 we develop a procedure to fit T 0 , γ, and η simultaneously by modeling the observed spectra with Doppler profiles. In an alternative approach the temperature T of an absorber, the He /H  ratio η, and the redshift scale of η variations are estimated simultaneously by optimizing the Doppler parameters of He .Results. Testing our procedure with artificial data shows that well-constrained results can be obtained only if the signal-to-noise ratio in the He  forest is S /N > ∼ 20. Additionally, ambiguities in the line profile decomposition may result in significant systematic errors. Thus, it is impossible to give an estimate of the temperature-density relation with the He  data available at present (S /N ∼ 5).However, we find that only 45% of the lines in our sample favor turbulent line widths while the remaining lines are probably affected by thermal broadening. Furthermore, the inferred η values are on average about 0.05 dex larger if a thermal component is taken into account, and their distribution is 46% narrower in comparison to a purely turbulent fit. Therefore, variations of η on a 10% level may be related to the presence of thermal line broadening. The apparent correlation between the strength of the H  absorption and the η value, which has been found in former studies assuming turbulent line broadening, essentially disappears if thermal broadening is taken into account. In the redshift range 2.58 < z < 2.74 towards the quasars HE 2347-4342 and HS 1700+6416 we obtain η ≈ 100 and slightly larger. In the same redshift range the far-UV spectrum of HS 1700+6416 is best and we estimate a mean value of log η = 2.11 ± 0.32 taking into account combined thermal and turbulent broadening.

show abstract

The Fluctuating Intergalactic Radiation Field at Redshiftsz= 2.3–2.9 from Heiiand HiAbsorption toward HE 2347−4342

Cited by 103 publications

References 33 publications

Fluctuations of the intergalactic ionization field at redshiftz~ 2

Fluctuations of the intergalactic ionization field at redshiftz~ 2

CONSTRAINTS ON QUASAR LIFETIMES AND BEAMING FROM THE He II Lyα FOREST

The HeII Lyman alpha forest and the thermal state of the IGM

Contact Info

Product

Resources

About