Implications for Cosmic Reionization from the Optical Afterglow Spectrum of the Gamma-Ray Burst 050904 at z = 6.3

By T. Totani, N. Kawai, G. Kosugi, K. Aoki, Toru Yamada, M. Iye, K. Ohta, T. Hattori. 2005

271 citations recorded by the source corpus.

The gamma-ray burst (GRB) 050904 at z =6 .3 provides the first opportunity to probe the intergalactic medium (IGM) by GRBs at the epoch of reionization. Here, we present a spectral modeling analysis of the optical afterglow spectrum taken by the Subaru Telescope, aiming to constrain the reionization history. The spectrum shows a clear damping wing at wavelengths redward of the Lyman break, and the wing shape can be fitted either by a damped Lyα system with a column density of log[NHI(cm −2 )] ∼ 21.6 at a redshift close to the detected metal absorption lines (zmetal =6 .295), or by almost neutral IGM extending to a slightly higher redshift of zIGM,u ∼ 6.36. In the latter case, the difference between the two redshifts may be explained by the acceleration of metal absorbing shells in the activities of the GRB or its progenitor. However, we exclude this possibility by using the light transmission feature around the Lyβ resonance, leading to a firm upper limit of zIGM,u ≤ 6.314. We then show evidence that the IGM was already largely ionized at z =6 .3 with the best-fit neutral fraction of IGM, xHI (≡ nHI/nH )=0 .00, and upper limits of xHI 6. Various systematic uncertainties are examined, but none of them appears large enough to change our conclusion. To get further information on the reionization, it is important to increase the sample size of z 6 GRBs, in order to find GRBs with low column densities (log NHI 20) within their host galaxies and to make statistical studies of Lyα line emission from host galaxies.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/705e28366acfa3b2b32cfaa987ed4d69396ab136

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The metallicity of the long GRB hosts and the fundamental metallicity relation of low-mass galaxies (2010, background): “Thank to they brightness, GRBs can be used as a background light to study the metal content of its parent galaxy even at very high-z as demonstrated by the case of GRB 050904 at z = 6.3 for which an estimate of the metallicity has been derived by Totani et al. (2006) and Kawai et al. (2006).”
Reionization and Galaxy Evolution Probed by z = 7 Lyα Emitters (2007, methodology): “This result is also supported by the spectral modeling analysis of the currently most distant GRB at z ∼ 6.3 conducted by Totani et al. (2006), placing the constraint of 0 ≤ xz∼6.3HI < 0.17–0.6.”
The Evolution of the Intergalactic Medium (2015, methodology): “Lyα damping wing optical depths: static cloud: τDW = 3 NHI 1020/cm2 ( 103km/s ∆v )2 neutral IGM: τDW = xHI ( 1+z 8.5 ) 3 2 10 3km/s ∆v This effect has been used to place constraints on the neutral fraction at z = 6.3 using the gamma ray burst observed on 05/09/04 (Totani et al. 2006).”
Full-data Results of Hubble Frontier Fields: UV Luminosity Functions at z ∼ 6–10 and a Consistent Picture of Cosmic Reionization (2017, background): “…al. (2011); Carilli et al. (2010); Chornock et al. (2013, 2014); Dijkstra et al. (2011); Konno et al. (2014); McGreer et al. (2011); McQuinn et al. (2007, 2008); Mesinger & Furlanetto (2008); Mesinger (2010); Ouchi et al. (2010); Ota et al. (2008); Patel et al. (2010); Totani et al. (2006, 2014).”
Efficient Simulations of Early Structure Formation and Reionization (2007, background): “Current observations paint a complex picture of the reionization epoch (Mesinger & Haiman 2004; Wyithe & Loeb 2004; Fan et al. 2006; Mesinger & Haiman 2006; Malhotra & Rhoads 2004; Furlanetto et al. 2006c; Malhotra & Rhoads 2006; Page et al. 2006; Kashikawa et al. 2006; Totani et al. 2006).”
The physics of the intergalactic medium (2007, background): “…have relied almost exclusively on the spectra of QSOs, although IGM absorption features have also been detected in the spectra of Gamma-Ray Bursts (GRBs) (Totani et al., 2006), and indeed played a key role in establishing the extragalactic character of some bursts (Metzger et al., 1997).”
Signatures of X-rays in the early Universe (2012, background): “Photons below our fiducial choice of hν0 = 300 eV have optical depths exceeding unity for NHI ∼> 10 21.5 cm−2, consistent with the column densities seen in high-redshift gamma-ray bursts (GRBs) (Totani et al. 2006; Greiner et al. 2009).”
HUBBLE FRONTIER FIELDS FIRST COMPLETE CLUSTER DATA: FAINT GALAXIES AT z ∼ 5–10 FOR UV LUMINOSITY FUNCTIONS AND COSMIC REIONIZATION (2014, background): “…moderately large neutral hydrogen fraction at z & 6 is implied by the Lyα damping wing absorption features in the spectra of gammaray bursts (GRBs) at z ∼ 6 (Totani et al. 2006, 2013) and Lyα emitters at z ∼ 6 − 7 (Kashikawa et al. 2006; Ouchi et al. 2010; Kashikawa et al. 2011; Konno et al. 2014).”
THE STAR FORMATION RATE IN THE REIONIZATION ERA AS INDICATED BY GAMMA-RAY BURSTS (2009, background): “…the whereabouts of these GRB hosts today, whether they continued to grow, merged into more massive halos, etc. Observations of the afterglow spectrum (e.g., Totani et al. 2006; McQuinn et al. 2008) could determine the extent that the host had experienced the effects of the reionizing UV background.”
Systematic Identification of LAEs for Visible Exploration and Reionization Research Using Subaru HSC (SILVERRUSH). I. Program strategy and clustering properties of ∼2000 Lyα emitters at z = 6–7 over the 0.3–0.5 Gpc2 survey area (2017, background): “…et al. 2006), as well as Lyα damping wing (DW) absorption measurements of QSOs (Mortlock et al. 2011; Bolton et al. 2011), gamma-ray bursts (GRBs; Totani et al. 2006, 2014, 2016; see also Greiner et al. 2009), and galaxies including LAEs (Malhotra & Rhoads 2004; Ouchi et al. 2010; Ota et al.…”
NEW CONSTRAINTS ON COSMIC REIONIZATION FROM THE 2012 HUBBLE ULTRA DEEP FIELD CAMPAIGN (2013, background): “To date, the best example of such a source is GRB050904 atz = 6.3, which received rapid followup and produced a high signal-to-noise spectrum (Totani et al. 2006).”
COSMIC MICROWAVE BACKGROUND CONSTRAINTS ON THE DURATION AND TIMING OF REIONIZATION FROM THE SOUTH POLE TELESCOPE (2011, background): “…10% at z = 7.1 (Mortlock et al. 2011); (3) the non-detection of intergalactic damping wing absorption in the spectrum of a gamma ray burst at z=6.3 (Totani et al. 2006; McQuinn et al. 2008); and (4) the number density and clustering of Lyα emitters (Malhotra & Rhoads 2004; Haiman & Cen 2005;…”