The UV spectrum of HS 1700+6416

Fechner, C.; Reimers, D.; Kriss, G. A.; Baade, Robert A.; Blair, William P.; Giroux, Mark L.; Green, R. F.; Moos, H. W.; Morton, Donald C.; Scott, J. S.; Shull, J. M.; Simcoe, Robert A.; Songaila, A.; Zheng, Wei

doi:10.1051/0004-6361:20064950

Cited by 76 publications

(176 citation statements)

References 53 publications

(113 reference statements)

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“…Measurements show the intergalactic He ii optical depth rises rapidly from z ¼ 2 to z ¼ 3:5, where it takes on a wide range of values (Zheng et al 2004a(Zheng et al , 2004bFechner et al 2006). The rapid rise and fluctuations are suggestive of the approach to the epoch of He ii reionization.…”

Section: Discussionmentioning

confidence: 98%

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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Section: Discussionmentioning

confidence: 98%

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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“…In that case, η ∼ 40-80 Zheng et al 2004;Fechner et al 2006;Fechner & Reimers 2007) implies r 0 ∼ 110-160 Mpc at z ∼ 2.5. A separate argument comes from matching the (measured) emissivity of the quasar population with the observed optical depth of the He ii forest.…”

Section: Quasars and Radiation Peaks: Finite Lifetimesmentioning

confidence: 95%

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

Furlanetto

Lidz

2011

ApJ

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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.

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“…While excluding orbital day data to minimize the scattered light component seems to be common in most of these investigations, they differ in other aspects. In Fechner et al (2006), the pulse height range was modified to reduce the background, while in Dixon et al (2006) they kept the standard pulse height limits with the argument of preserving photometric accuracy. In Zheng et al (2004), they extended the analysis and reduced the (night only) data with both the standard pipeline procedure and a manual extraction.…”

Section: Observations Reductions and Data Analysismentioning

confidence: 99%

Analyzing low signal-to-noise FUSE spectra

Leitet

Bergvall

Piskunov

et al. 2011

A&A

101

105

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Context. Galaxies are believed to be the main providers of Lyman continuum (LyC) photons during the early phases of the cosmic reionization. Little is known however, when it comes to escape fractions and the mechanisms behind the leakage. To learn more, one may look at local objects, but so far only one low-z galaxy has shown any signs of emitting LyC radiation. With data from the Far Ultraviolet Spectroscopic Explorer (FUSE), we previously found an absolute escape fraction of ionizing photons ( f esc ) of 4-10% for the blue compact galaxy Haro 11. However, using a revised version of the reduction pipeline on the same data set, Grimes and collaborators were unable to confirm this and derived an upper limit of f esc 2% . Aims. We attempt to determine whether Haro 11 is emitting ionizing radiation to a significant level or not. We also investigate the performance of the reduction pipeline for faint targets such as Haro 11, and introduce a new approach to the background subtraction. Methods. The final version of the reduction pipeline, CalFUSE v3.2, was applied to the same Haro 11 data set as the two previous authors used. At these faint flux levels, both FUSE and CalFUSE are pushed to their limits, and a detailed analysis was undertaken to monitor the performance of the pipeline. We show that non-simultaneous background estimates are insuffient when working with data of low signal-to-noise ratio (S /N), and a new background model was developed based on a direct fit to the detector response. Results. We find that one has to be very careful when using CalFUSE v3.2 on low S /N data, and especially when dealing with sources where signal might originate from off-center regions. Applying the new background fit, a significant signal is detected in the LyC in both detector segments covering these wavelengths. Thus, the leakage is confirmed with a flux density of f 900 = 4.0 × 10 −15 erg s −1 cm −2 Å −1 (S /N = 4.6), measured on the airglow free regions in the LyC for the night-only data. This corresponds to an absolute escape fraction of ionizing photons from Haro 11 of f esc = 3.3 ± 0.7%. We confirm these results by investigating the two-dimensional data, the count rates, and the residual flux in C ii λ1036 Å.

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The UV spectrum of HS 1700+6416

Cited by 76 publications

References 53 publications

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

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

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

Analyzing low signal-to-noise FUSE spectra

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