Detection of intergalactic ionized helium absorption in a high-redshift quasar

Jakobsen, P.; Boksenberg, A.; Deharveng, J. M.; Greenfield, P.; Jędrzejewski, R.; Paresce, Francesco

doi:10.1038/370035a0

Cited by 222 publications

(202 citation statements)

References 34 publications

Supporting

Mentioning

194

Contrasting

Order By: Relevance

“…If the continuum flux is '4 ; 10 À17 ergs s À1 cm À2 8 À1 , the emission feature near 1510 8 may be the red wing of a broad He ii Ly emission line. Similar broad He ii Ly emission lines, with FWHM > 10 4 km s À1 , are also shown in quasar HS 1700+64 (z ¼ 2:73; Davidsen et al 1996;Fechner et al 2006) and Q0302-004 (z ¼ 3:29;Jakobsen et al 1994;Heap et al 2000). The distortion of the emission line blueward of the peak is suggestive of strong absorption.…”

Section: Observations and Data Reductionmentioning

confidence: 61%

“…He ii absorption is therefore an important probe of the evolution of the IGM. Since its first detection at z ¼ 3:3 (Jakobsen et al 1994), such a feature has been progressively found in quasar spectra at higher redshifts: z ¼ 3:5 (Zheng et al 2004a) and z ¼ 3:8 (Zheng et al 2005). Measurements of the intergalactic helium and hydrogen Ly opacities show He ii was ionized to He iii before z ' 2:8 (Reimers et al 1997;Kriss et al 2001), while intergalactic hydrogen was ionized before z ' 6 (Fan et al 2002).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

View full text Add to dashboard Cite

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.

show abstract

Section: Observations and Data Reductionmentioning

confidence: 61%

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

View full text Add to dashboard Cite

show abstract

“…This may be an indication that hydrogen at least partially recombined after the first epoch of reionization, only to be reionized again at a lower redshift. In contrast to the epoch of hydrogen reionization, the epoch of helium reionization has been firmly identified at z ' -^ 3 through the detection of a Gurm-Peterson trough in quasar spectra (Jakobsen et al [17], Davidsen et al [18], Heap et al [19]). …”

Section: Jwst Studies Of Reionizationmentioning

confidence: 99%

A Spitzer Warm Mission Ultra-Wide Survey As A Target Finder For The James Webb Space Telescope

Gardner

Fan

Wilson

et al. 2007

AIP Conference Proceedings

View full text Add to dashboard Cite

Abstract. The James Webb Space Telescope (JWST) is the successor to the Hubble and Spitzer Space Telescopes. It has a broad scientific mission which includes spectroscopic studies of the epoch of reionization through observations of z > 8 quasars. The Spitzer warm mission provides a unique opportunity to conduct an infrared survey of several hundred square degrees to a depth of several micro-Janskys, capable of finding quasars out to z = 10. Deep JWST continuum spectroscopy of these quasars will establish the epoch and history of the Universe through detection of the GunnPeterson trough and/or Lyman-a damping wings. The statistics and luminosity function of high-z quasars will reveal the early history of accretion in the most extreme systems, providing insights in the role of black holes in galaxy evolution. Data obtained from an ultra-wide warm Spitzer survey will also be useful for other science, including studies of high-redshift galaxy clusters.Keywords: Spitzer Space Telescope, infrared astronomical observations, extragalactic objects, origin and formation of the universe PACS: 95.85. Hp, 98.62.Py 98.62.Ai, 98.80.Bp

show abstract

“…In general, the Cramér-Rao lower variance bound can be used to cover a broad span of applications, ranging from instrument design for specific target accuracy goals, to observational planning, and to data analysis benchmarking (see., e.g., Perryman et al (1989), Jakobsen et al (1992), Zaccheo et al (1995), Adorf (1996)). For example, the Cramér-Rao bound can be used to predict how a particular design choice (pixel size, readout noise, etc.)…”

Section: Introductionmentioning

confidence: 99%

Analysis of the Cramér-Rao Bound in the Joint Estimation of Astrometry and Photometry

Mendez

Silva²,

Orostica³

et al. 2014

Publications of the Astronomical Society of the Pacific

View full text Add to dashboard Cite

In this paper we use the Cramér-Rao lower uncertainty bound to estimate the maximum precision that could be achieved on the joint simultaneous (or 2D) estimation of photometry and astrometry of a point source measured by a linear CCD detector array.1 On leave at the European Southern Observatory, Casilla 19001, Santiago, Chile.-2 -We develop exact expressions for the Fisher matrix elements required to compute the Cramér-Rao bound in the case of a source with a Gaussian light profile. From these expressions we predict the behavior of the Cramér-Rao astrometric and photometric precision as a function of the signal and the noise of the observations, and compare them to actual observations -finding a good correspondence between them.From the Cramér-Rao bound we obtain the well known fact that the uncertainty in flux on a Poisson-driven detector, such as a CCD, goes approximately as the square root of the flux. However, more generally, higher order correction factors that depend on the ratio B/F or F/B (where B is the background flux per pixel and F is the total flux of the source), as well as on the properties of the detector (pixel size) and the source (width of the light profile), are required for a proper calculation of the minimum expected uncertainty bound in flux. Overall the Cramér-Rao bound predicts that the uncertainty in magnitude goes as (S/N ) −1 under a broad range of circumstances.As for the astrometry we show that its Cramér-Rao bound also goes as (S/N ) −1 but, additionally, we find that this bound is quite sensitive to the value of the backgroundsuppressing the background can greatly enhance the astrometric accuracy.We present a systematic analysis of the elements of the Fisher matrix in the case when the detector adequately samples the source (oversampling regime), leading to closed-form analytical expressions for the Cramér-Rao bound. We show that, in this regime, the joint parametric determination of photometry and astrometry for the source become decoupled from each other, and furthermore, it is possible to write down expressions (approximate to first order in the small quantities F/B or B/F ) for the expected minimum uncertainty in flux and position. These expressions are shown to be quite resilient to the oversampling condition, and become thus very valuable benchmark tools to estimate the approximate behavior of the maximum photometric and astrometric precision attainable under pre-specified observing conditions and detector properties.

show abstract

Detection of intergalactic ionized helium absorption in a high-redshift quasar

Cited by 222 publications

References 34 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

A Spitzer Warm Mission Ultra-Wide Survey As A Target Finder For The James Webb Space Telescope

Analysis of the Cramér-Rao Bound in the Joint Estimation of Astrometry and Photometry

Contact Info

Product

Resources

About