An improved measurement of the flux distribution of the Lyα forest in QSO absorption spectra: the effect of continuum fitting, metal contamination and noise properties

By T.-S. Kim, J. Bolton, M. Viel, M. Haehnelt, R. P. L. F. A. Potsdam, Potsdam, Heidelberg · Germany, I. O. Astronomy, Cambridge, UK. and 5 more. 2007

138 citations recorded by the source corpus.

We have performed an extensive Voigt profile analysis of the neutral hydrogen (H i) and metal absorption present in a sample of 18 high-resolution, high signal-to-noise ratio quasi-stellar object (QSO) spectra observed with the Very Large Telescope Ultraviolet and Visual Echelle Spectrograph. We use this analysis to separate the metal contribution from the H absorption and present an improved measurement of the flux probability distribution function (PDF) due to H i absorption alone at (z) = 2.07,2.52 and 2.94. The flux PDF is sensitive to the continuum fit in the normalized flux range 0.8 < F < 1.0 and to metal absorption at 0.2 < F < 0.8. Our new measurements of the flux PDF due to H i absorption alone are systematically lower at 0.2 < F < 0.8 by up to 30 per cent compared to the widely used measurement of McDonald et al., based on a significantly smaller sample of Keck High Resolution Echelle Spectrometer data. This discrepancy is probably due to a combination of our improved removal of the metal absorption and cosmic variance, since variations in the flux PDF between different lines-of-sight are large. The H effective optical depth τ eff Ht at 1.7 < z < 4 is best fit with a single power law, τ eff HI = (0.0023 ± 0.0007)(1 + z) 365±0.21 , in good agreement with previous measurements from comparable data. As also found previously, the effect of noise on the flux distribution is not significant in high-resolution, high signal-to-noise ratio data.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/a6e236dee3e577a5bb2c0e857146287db9c3ed66

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Citations in the corpus

The Giant Gemini GMOS survey of zem > 4.4 quasars – I. Measuring the mean free path across cosmic time (2014, background): “Studies of the IGM across cosmic time have revealed redshift evolution in many properties of the Lyα forest: temperature (e.g. Lidz et al. 2010; Becker et al. 2011), line density (e.g. Kim et al. 2013), and the flux PDF (e.g. Becker et al. 2007; Kim et al. 2007).”
A refined measurement of the mean transmitted flux in the Lyα forest over 2 < z < 5 using composite quasar spectra (2012, background): “…that the peaks of the Lyα forest transmission should approach the continuum (e.g., Rauch et al. 1997; McDonald et al. 2000; Schaye et al. 2003; Songaila 2004; Kirkman et al. 2005; Kim et al. 2007; Becker et al. 2007; Faucher-Giguère et al. 2008; Dall’Aglio et al. 2008; Becker et al. 2011).”
Evidence of patchy hydrogen reionization from an extreme Lyα trough below redshift six (2014, background): “Metal lines, at least at z < 5, generally account for only a few percent of the absorption in the Lyα forest (Schaye et al. 2003; Kirkman et al. 2005; Kim et al. 2007; Becker et al. 2011a), and so are not expected to strongly affect τeff measurements at z & 4 or add significantly to their scatter…”
Evolution of the Intergalactic Opacity: Implications for the Ionizing Background, Cosmic Star Formation, and Quasar Activity (2008, methodology): “Comparing an improved measurement of the Lyα forest flux PDF at 1.7 < z < 3.2 by Kim et al. (2007) to a large set of hydrodynamical simulations with different cosmological parameters and thermal histories, Bolton et al. (2007) find evidence for an equation that is close to isothermal, or even…”
FIVE-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE OBSERVATIONS: COSMOLOGICAL INTERPRETATION (2008, unknown): “…et al. 2007); the relationship between gas temperature and density appears to be more complicated than assumed in the previous Lyα forest analysis (Kim et al. 2007; Bolton et al. 2008); and additional astrophysics could potentially be the source of some of the small scale fluctuations seen in…”
The Evolution of the Intergalactic Medium (2015, methodology): “After the Lyα forest power spectrum, the Lyα forest transmission PDF is the most studied statistic (e.g. McDonald et al. 2000; Lidz et al. 2006; Kim et al. 2007; Lee et al. 2015).”
A Direct Precision Measurement of the Intergalactic Lyα Opacity at 2 ≤ z ≤ 4.2 (2007, background): “…the other hand, metal lines coincident with absorption already saturated by hydrogen have little to no impact on the effective optical depth (e.g., Kim et al. 2007), so that it is unclear whether the larger fraction of missed lines at higher redshifts actually makes the estimated correction less…”