NEW OBSERVATIONS OF z ∼ 7 GALAXIES: EVIDENCE FOR A PATCHY REIONIZATION

By L. Pentericci, E. Vanzella, A. Fontana, M. Castellano, T. Treu, A. Mesinger, M. Dijkstra, A. Grazian, M. Bradač, Christopher J. Conselice and 10 more. 2014

177 citations recorded by the source corpus.

We present new results from our search for z ∼ 7 galaxies from deep spectroscopic observations of candidate z dropouts in the CANDELS fields. Despite the extremely low flux limits achieved by our sensitive observations, only two galaxies have robust redshift identifications, one from its Lyα emission line at z = 6.65, the other from its Lyman break, i.e., the continuum discontinuity at the Lyα wavelength consistent with a redshift of 6.42 but with no emission line. In addition, for 23 galaxies we present deep limits in the Lyα equivalent width derived from the nondetections in ultradeep observations. Using this new data as well as previous samples, we assemble a total of 68 candidate z ∼ 7 galaxies with deep spectroscopic observations, of which 12 have a line detection. With this much enlarged sample we can place solid constraints on the declining fraction of Lyα emission in z ∼ 7 Lyman-break galaxies compared to z ∼ 6, both for bright and faint galaxies. Applying a simple analytical model, we show that the present data favor a patchy reionization process rather than a smooth one.

Subfields: Astronomy and Astrophysics, Electrical and Electronic Engineering, Instrumentation

View Paper: https://www.semanticscholar.org/paper/7f71442ad3a97dcbf0ff285dcfe64c07ed87f2b2

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In Astronomy and Astrophysics

1. Richard S. Ellis
2. P. Oesch
3. R. Bouwens
4. G. Illingworth
5. P. V. van Dokkum
6. M. Franx
7. J. Dunlop
8. I. Labbé

In Electrical and Electronic Engineering

1. Richard S. Ellis
2. R. Bouwens
3. P. Oesch
4. G. Illingworth
5. D. Stark
6. J. Dunlop
7. I. Labbé
8. M. Franx

In Instrumentation

1. Richard S. Ellis
2. R. Bouwens
3. P. Oesch
4. P. V. van Dokkum
5. M. Franx
6. I. Labbé
7. G. Illingworth
8. J. Dunlop

Citations in the corpus

• Lyα and C iii] emission in z = 7–9 Galaxies: accelerated reionization around luminous star-forming systems? (2016, methodology): “These surveys clearly reveal a rapidly declining Lyα emitter fraction over 6 < z < 8 (e.g., Stark et al. 2010; Fontana et al. 2010; Ono et al. 2012; Pentericci et al. 2014; Tilvi et al. 2014; Schenker et al. 2014), similar to the drop in the abundance of narrowbandselected Lyα emitters over 5.7 < z…”
• REIONIZATION AFTER PLANCK: THE DERIVED GROWTH OF THE COSMIC IONIZING EMISSIVITY NOW MATCHES THE GROWTH OF THE GALAXY UV LUMINOSITY DENSITY (2015, background): “…the real uncertainties on QH II are likely larger than the formal uncertainties quoted by S14, as can be seen by comparing the different estimates for QH II quoted by S14 based on the same set of observations or using the results from other studies (Pentericci et al. 2014; Tilvi et al. 2014).”
• The Universe Is Reionizing at z ∼ 7: Bayesian Inference of the IGM Neutral Fraction Using Lyα Emission from Galaxies (2017, methodology): “(iv) We conduct a Bayesian inference from current observations at z ∼ 7 from Pentericci et al. (2014) and infer the first direct constraint on the neutral fraction from Lyα transmission of xhi = 0.59 +0.11 −0.15, which is consistent with other robust probes of the neutral fraction and confirms…”
• A SPECTROSCOPIC REDSHIFT MEASUREMENT FOR A LUMINOUS LYMAN BREAK GALAXY AT z = 7.730 USING KECK/MOSFIRE (2015, background): “…rate of spectroscopic follow-up surveys is likely caused by a decreased fraction of galaxies showing strong Lyα emission due to an increased neutral fraction in the inter-galactic medium (IGM) at z > 6 (Stark et al. 2010, 2011; Treu et al. 2013; Schenker et al. 2012, 2014; Pentericci et al. 2014).”
• Identification of the brightest Lyα emitters at z = 6.6 : Implications for the evolution of the luminosity function in the reionization era (2015, background): “…> 7 spectroscopic follow-up of LBGs is remarkably less successful (Fontana et al. 2010; Stark et al. 2010; Pentericci et al. 2011; Treu et al. 2013; Pentericci et al. 2014; Caruana et al. 2014), indicating either a lower intrinsic escape of Lyα (e.g. Dijkstra et al. 2014), an increased column…”
• 21CMMC: an MCMC analysis tool enabling astrophysical parameter studies of the cosmic 21 cm signal (2015, background): “…such constraints can be obtained from the spectra of high-z quasars such as ULAS J1120+0641 (Bolton et al. 2011; Mortlock et al. 2011) or from the observed drop in Lyman-α emission from high-z galaxies (e.g. Caruana et al. 2014; Pentericci et al. 2014; Dijkstra et al. 2014; Mesinger et al. 2015).”
• COSMIC REIONIZATION AND EARLY STAR-FORMING GALAXIES: A JOINT ANALYSIS OF NEW CONSTRAINTS FROM PLANCK AND THE HUBBLE SPACE TELESCOPE (2015, background): “…years exploits the fraction of star forming galaxies showing Lymanα emission (e.g., Stark et al. 2010) now extended to z ∼ 7 − 8 from Treu et al. (2013), Pentericci et al. (2014) and Schenker et al. (2014), the Lyman-α damping wing absorption constraints from GRB host galaxies by Chornock et al.…”
• The Evolution of the Intergalactic Medium (2015, background): “…between z = 6 and 7, and again between z = 7 and 8, in the fraction of dropout galaxies that show significant Lyα emission (Schenker et al. 2012; Ono et al. 2012; Pentericci et al. 2014; Tilvi et al. 2014), after an increase in this quantity between z = 4 and z = 6 (see the right panel in Fig.”
• Lyα Emitting Galaxies as a Probe of Reionisation (2014, background): “…2010; Stark, Ellis, & Ouchi 2011; Pentericci et al. 2011; Schenker et al. 2012; Ono et al. 2012; Caruana et al. 2012, 2013; Finkelstein et al. 2013; Pentericci et al. 2014; Schenker et al. 2014; Tilvi et al. 2014), in line with observations of the Lyα and UV luminosity functions of LAEs (again…”
• Faint AGNs at z > 4 in the CANDELS GOODS-S field: looking for contributors to the reionization of the Universe (2015, background): “…the large decline of strong Lyman-α emitting galaxies observed between z ∼ 6 and z ∼ 7 which would suggest a large neutral hydrogen fraction in the IGM and a patchy reionization process already at z ∼ 7 (Pentericci et al. (2011), Treu et al. (2013), Pentericci et al. (2014), Tilvi et al. (2014)).”
• ARE ULTRA-FAINT GALAXIES AT z = 6–8 RESPONSIBLE FOR COSMIC REIONIZATION? COMBINED CONSTRAINTS FROM THE HUBBLE FRONTIER FIELDS CLUSTERS AND PARALLELS (2015, background): “In particular, the prevalence of Lyα emitters (LAEs) among continuum selected galaxies (LBGs) appears to drop very rapidly at z > 6.5, which suggests an increase in the fraction of neutral hydrogen (Stark et al. 2010; Treu et al. 2013; Schenker et al. 2014a; Pentericci et al. 2014).”
• HUBBLE FRONTIER FIELDS FIRST COMPLETE CLUSTER DATA: FAINT GALAXIES AT z ∼ 5–10 FOR UV LUMINOSITY FUNCTIONS AND COSMIC REIONIZATION (2014, background): “Similarly, there are reports of Lyα-emitting galaxy fraction drops at z ∼ 7 probably due to the increase of Lyα damping wing absorption given by the neutral hydrogen in the IGM (Pentericci et al. 2011, 2014; Ono et al. 2012; Schenker et al. 2012, 2014; Treu et al. 2013; Finkelstein et al. 2013).”
• Full-data Results of Hubble Frontier Fields: UV Luminosity Functions at z ∼ 6–10 and a Consistent Picture of Cosmic Reionization (2017, background): “Observational studies show that the reionization occurred at z & 6 (Fan et al. 2006; Pentericci et al. 2011, 2014; Ono et al. 2012; Totani et al. 2006, 2014; Kashikawa et al. 2011; Ouchi et al. 2010; Konno et al. 2014; Treu et al. 2013).”
• Lyα EMISSION FROM A LUMINOUS z = 8.68 GALAXY: IMPLICATIONS FOR GALAXIES AS TRACERS OF COSMIC REIONIZATION (2015, background): “Secondly, simulations suggest that reionization is likely to be a patchy process (Taylor & Lidz 2014) and thus conclusions drawn from the modest samples of spectroscopically-targeted galaxies may be misleading (Treu et al. 2012; Pentericci et al. 2014; Tilvi et al. 2014).”
• EVIDENCE FOR PopIII-LIKE STELLAR POPULATIONS IN THE MOST LUMINOUS Lyα EMITTERS AT THE EPOCH OF REIONIZATION: SPECTROSCOPIC CONFIRMATION (2015, background): “It is likely that re-ionisation was very heterogeneous/patchy (e.g. Pentericci et al. 2014), with the early high density regions re-ionising first, followed by the rest of the Universe.”
• CONTRASTING GALAXY FORMATION FROM QUANTUM WAVE DARK MATTER, ψDM, WITH ΛCDM, USING PLANCK AND HUBBLE DATA (2015, background): “5 7.0 from the statistical absence of strong Lyα emission from the most distant galaxies amenable to spectroscopy (Pentericci et al. 2014; Stark et al. 2015).”