The Giant Gemini GMOS survey of zem > 4.4 quasars – I. Measuring the mean free path across cosmic time

By G. Worseck, J. Xavier Prochaska, John M. O’Meara, George D. Becker, S. Ellison, S. López, A. Meiksin, B. M'enard, Michael T. Murphy, Michele Fumagalli. 2014

148 citations recorded by the source corpus.

We have obtained spectra of 163 quasars at zem > 4.4 with the Gemini Multi Object Spectrometers, the largest publicly available sample of high-quality, low-resolution spectra at these redshifts. From this data set, we generated stacked quasar spectra in three redshift intervals at z ∼ 5 to model the average rest-frame Lyman continuum flux and to assess the mean free path λ 912 of the intergalactic medium to H I-ionizing radiation. At mean redshifts zq =(4.56, 4.86, 5.16), we measure λ 912 = (22.2 ± 2.3,15.1 ± 1.8,10.3 ± 1.6) h −1 proper Mpc with uncertainties dominated by sample variance. Combining our results with measurements from lower redshifts, the data are well modelled by a power law λ 912 = A[(1 + z) /5] η with A = (37 ± 2) h −1 Mpc and η =− 5.4 ± 0.4 at 2.3 <z< 5.5. This rapid evolution requires a physical mechanism – beyond cosmological expansion – which reduces the effective Lyman limit opacity. We speculate that the majority of H I Lyman limit opacity manifests in gas outside galactic dark matter haloes, tracing large-scale structures (e.g. filaments) whose average density and neutral fraction decreases with cosmic time. Our measurements of the mean free path shortly after H I reionization serve as a valuable boundary condition for numerical models thereof. Our measured λ 912 ≈ 10 Mpc at z =5.2 confirms that the intergalactic

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/9827d6f59f95cf576e058cf4c389e3c62d00a3db

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Nuclear and High Energy Physics

Citations in the corpus

COSMIC REIONIZATION AFTER PLANCK: COULD QUASARS DO IT ALL? (2015, methodology): “…ionizing intensity J using the emissivity in Equation (1), a EUV spectrum with αeuv = 1.7, and a new a piecewise parameterization of the distribution in redshift and column density of intergalactic absorbers that fits the measurements of the mean free path of 1 ryd photons by Worseck et al. (2014).”
An updated analytic model for attenuation by the intergalactic medium (2014, methodology): “Here we follow the method updated by O’Meara et al. (2013) (see also Fumagalli et al. 2013; Worseck et al. 2014).”
The Neutral Hydrogen Cosmological Mass Density at z = 5 (2015, methodology): “For a detailed description of the GGG spectra and the procedure used to reduce them, see Worseck et al. (2014).”
The first ultraviolet quasar-stacked spectrum at z ≃ 2.4 from WFC3 (2015, background): “The proper mean free path to Lyman limit photons is well described by a power law λmfp,912 = 37 ( 1 + z 5 )−5.4 Mpc (8) at 2.3 < z < 5.5 (Worseck et al. 2014), whereas its frequency dependence is λmfp (ν, z) = λmfp,912 ( ν ν912 )1.5 (9) for a column density distribution f (NH I, z) ∝ N−1.5H I…”
Faint AGNs at z > 4 in the CANDELS GOODS-S field: looking for contributors to the reionization of the Universe (2015, methodology): “…larger than z ∼ 7 since moderately bright ionizing sources with a maximum comoving density of ∼ 2 × 10−5 Mpc−3 at z ∼ 6 have a typical separation of ∼ 3 proper Mpc, only a factor 2 smaller respect to the derived proper mean free path of ionizing photons in the IGM at z ∼ 6 Worseck et al. (2014).”
The Evolution of the Intergalactic Medium (2015, methodology): “…dependences of the sources’ spectra and using the latest measurements by a factor of two over the mean, where n is the number density of sources and the mean free path to be absorbed by hydrogen is λmfp ≈ 200[(1 + z)/5]−4(ν/νHI)3(β−1) comoving Mpc over 2.3 < z < 5.5 (Worseck et al. 2014b).”
Inferring the astrophysics of reionization and cosmic dawn from galaxy luminosity functions and the 21-cm signal (2018, background): “The fiducial one is consistent with the mean free path measurements of Worseck et al. (2014) which are at z ≤ 5.2, though D’Aloisio et al. (2018b) argue this might be an overestimate due to a bias from including the proximity zone in the mean free path calculation.”
Evolution of the AGN UV luminosity function from redshift 7.5 (2018, background): “…i, z) measurements at z < 3.5, and roughly reproduces both the H i Lyα effective optical depth (but not in detail—see Puchwein et al. 2015; Bolton et al. 2017; Oñorbe et al. 2017) and the measured mean free path to H i Lyman limit photons at z < 5.5 (Prochaska et al. 2009; Worseck et al. 2014).”
New Constraints on the free-streaming of warm dark matter from intermediate and small scale Lyman-$\alpha$ forest data (2017, methodology): “The updated model uses the more recent mean free path measurements of [36] and parameterizes the effect of UV fluctuations on the flux power spectrum as fUV – defined as the fraction of the volume averaged hydrogen photo-ionisation rate that arises from a fluctuating QSO component.”
Evidence of patchy hydrogen reionization from an extreme Lyα trough below redshift six (2014, methodology): “6 (Prochaska et al. 2009; Songaila & Cowie 2010; O’Meara et al. 2013; Rudie et al. 2013; Worseck et al. 2014).”
Large Ly α opacity fluctuations and low CMB τ in models of late reionization with large islands of neutral hydrogen extending to z < 5.5 (2018, background): “…observed distribution of τeff at z = 5.6, albeit with a rather short mean free path that decreases rapidly with distance from (bright) ionizing sources and that is in the mean a factor of 3.6 smaller than that expected from an extrapolation of measurements at z = 4.56–5.16 (Worseck et al. 2014).”
An extreme [O III] emitter at z = 3.2: a low metallicity Lyman continuum source (2015, background): “Unfortunately, it is not possible to directly detect Lyman continuum emission at the epoch of reionization or even in the aftermath (e.g., at any redshift z > 4.5), due to the very high cosmic opacity (e.g., Worseck et al. 2014).”