REIONIZATION AFTER PLANCK: THE DERIVED GROWTH OF THE COSMIC IONIZING EMISSIVITY NOW MATCHES THE GROWTH OF THE GALAXY UV LUMINOSITY DENSITY

By R. Bouwens, G. Illingworth, P. Oesch, J. Caruana, B. Holwerda, R. Smit, S. Wilkins. 2015

258 citations recorded by the source corpus.

Thomson optical depth τ measurements from Planck provide new insights into the reionization of the universe. In pursuit of model-independent constraints on the properties of the ionizing sources, we determine the empirical evolution of the cosmic ionizing emissivity. We use a simple two-parameter model to map out the evolution in the emissivity at z ≳ 6 from the new Planck optical depth τ measurements, from the constraints provided by quasar absorption spectra and from the prevalence of Lyα emission in z ∼ 7–8 galaxies. We find the redshift evolution in the emissivity N ˙ ion ( z ) ?> required by the observations to be ( d log 10 N ˙ ion / dz ) z = 8 = − 0.15 − 0.11 + 0.08 ?> ( ( d log 10 N ˙ ion / dz ) z = 8 = − 0.19 − 0.11 + 0.09 ?> for a flat prior), largely independent of the assumed clumping factor CH ii and entirely independent of the nature of the ionizing sources. The trend in N ˙ ion ( z ) ?> is well-matched by the evolution of the galaxy UV-luminosity density ( d log 10 &rgr; UV / dz = − 0.11 ± 0.04 ?> ) to a magnitude limit ≳−13 mag, suggesting that galaxies are the sources that drive the reionization of the universe. The role of galaxies is further strengthened by the conversion from the UV luminosity density ρUV to N ˙ ion ( z ) ?> being possible for physically plausible values of the escape fraction fesc, the Lyman-continuum photon production efficiency ξion, and faint-end cut-off Mlim to the luminosity function. Quasars/active galactic nuclei appear to match neither the redshift evolution nor normalization of the ionizing emissivity. Based on the inferred evolution in the ionizing emissivity, we estimate that the z ∼ 10 UV-Iuminosity density is 8−4+15× lower than at z ∼ 6, consistent with the observations. The present approach of contrasting the inferred evolution of the ionizing emissivity with that of the galaxy UV luminosity density adds to the growing observational evidence that faint, star-forming galaxies drive the reionization of the universe.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/85449919e6e06e8427dfe607f38cc9c4636faca1

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In Astronomy and Astrophysics

1. L. Hernquist
2. Richard S. Ellis
3. P. Hopkins
4. P. V. van Dokkum
5. P. Oesch
6. C. Conroy
7. R. Bouwens
8. R. Dav'e

In Atomic and Molecular Physics, and Optics

1. M. McQuinn
2. A. Mesinger
3. Judd D. Bowman
4. S. Furlanetto
5. G. Illingworth
6. G. Worseck
7. R. Bouwens
8. B. Greig

In Instrumentation

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

Citations in the corpus

• SILVERRUSH. IV. Lyα luminosity functions at z = 5.7 and 6.6 studied with ∼1300 Lyα emitters on the 14–21 deg2 sky (2017, background): “The best-fit faint-end slope values are α = −2.5−−2.6 (Table 4), which may indicate that the faint-end slopes of Lyα LFs are steeper than those of the UV LFs at similar redshifts (e.g., Bouwens et al. 2015b).”
• Low-redshift Lyman continuum leaking galaxies with high [O iii]/[O ii] ratios (2018, background): “Two competitive possible sources of ionization, active galactic nuclei (AGN) (Madau & Haardt 2015) and low-mass star-forming galaxies (SFGs) (Ouchi et al. 2009; Wise & Chen 2009; Mitra, Ferrara & Choudhury 2013; Yajima, Choi & Nagamine 2011; Bouwens et al. 2015), were proposed.”
• Radiation Backgrounds at Cosmic Dawn: X-Rays from Compact Binaries (2016, methodology): “We have checked that our fiducial model agrees to within 15% in the redshift range 5.5 ∼< z ∼< 10 with the UV luminosity densities derived by Bouwens et al. (2015) under the assumption of a faint-end LF cut-off of Mlim = −16 mag.”
• The Evolution of the Intergalactic Medium (2015, background): “The curved bands in the righthand panel of www.annualreviews.org • intergalactic medium 29 Figure 10 show the estimated photon emissivity from the observed galaxies as a function of their fesc, from Finkelstein et al. (2012a); see also Bouwens et al. (2015a).”
• J1154+2443: a low-redshift compact star-forming galaxy with a 46 per cent leakage of Lyman continuum photons (2017, background): “…it is generally thought that numerous fainter lowmass SFGs, below the current detection limit of observations, are responsible for the bulk of the ionizing radiation at z & 6 (Ouchi et al. 2009; Wise & Chen 2009; Mitra, Ferrara & Choudhury 2013; Yajima, Choi & Nagamine 2011; Bouwens et al. 2015).”
• The HDUV Survey: A Revised Assessment of the Relationship between UV Slope and Dust Attenuation for High-redshift Galaxies (2017, methodology): “The ionizing photon production efficiency is typically computed by combining Balmer emission lines, such as Hα, with UV continuum measurements (e.g., Bouwens et al. 2015), but both the lines and the continuum must be corrected for dust attenuation.”
• The realm of the galaxy protoclusters (2016, background): “…for reionization, such as individual stars, galaxies and (mini-)quasars, it seems likely that the stars of the first generation of galaxies were responsible for producing the bulk of the Lyman continuum photons that ionized the neutral IGM (e.g., see Robertson et al., 2015; Bouwens et al., 2015b).”
• CONTRASTING GALAXY FORMATION FROM QUANTUM WAVE DARK MATTER, ψDM, WITH ΛCDM, USING PLANCK AND HUBBLE DATA (2015, methodology): “M 13lim , in agreement with the findings of Bouwens et al. (2015a) and Robertson et al. (2015).”
• ALMA SPECTROSCOPIC SURVEY IN THE HUBBLE ULTRA DEEP FIELD: THE INFRARED EXCESS OF UV-SELECTED z = 2–10 GALAXIES AS A FUNCTION OF UV-CONTINUUM SLOPE AND STELLAR MASS (2016, methodology): “This is very close to the efficiency 25.53+0.06−0.06 Bouwens et al. (2015) had previously derived for z ∼ 4-5 galaxies with the bluest UV continuum slopes β (β < −2.3) and very close to the values suggested by the stellar population models including the impact of binary stars on the evolution…”
• Conditions for Reionizing the Universe with a Low Galaxy Ionizing Photon Escape Fraction (2019, methodology): “One key difference between the results of Bouwens et al. (2015a) and our own is that our inferred emissivity increases with increasing redshift over 6<z<10, which is a consequence of our lower average escape fraction over this epoch (see Section 5.2).”
• Hydrogen Epoch of Reionization Array (HERA) (2016, background): “8 (Schenker et al. 2013; Bouwens et al. 2015b) and are pushing deeper (e.g. McLeod et al. 2015), but producing a consistent ionization history requires broad extrapolations to lower-mass galaxies and ad hoc assumptions about the escape fraction of ionizing photons and the faint-end cutoff of…”
• Inferences on the timeline of reionization at z ∼ 8 from the KMOS Lens-Amplified Spectroscopic Survey (2019, background): “stars and galaxies: considered to be the primary producers of hydrogen-ionizing photons (e.g., Lehnert & Bremer 2003; Bouwens et al. 2003; Yan & Windhorst 2004; Bunker et al. 2004; Shull et al. 2012; Bouwens et al. 2015).”
• Consistent modelling of the meta-galactic UV background and the thermal/ionization history of the intergalactic medium (2018, background): “The above SFRD is consistent in the redshift range 5.5 ∼< z ∼< 10 with the UV luminosity densities derived by Bouwens et al. (2015) under MNRAS 000, 000–000 (0000) the assumption of a faint-end luminosity function cut-off of Mlim = −13 mag, deeper than what was assumed by Madau & Fragos (2017)…”
• Planck intermediate results. XLVI. Reduction of large-scale systematic effects in HFI polarization maps and estimation of the reionization optical depth (2016, unknown): “…of full reionization provided by Lyman-α absorption in the spec- ∗Corresponding author: J. L. Puget, jean-loup.puget@ias.u-psud.fr tra of high redshift objects (see Dijkstra 2014; Mashian et al. 2016; Robertson et al. 2015; Bouwens et al. 2015; Zitrin et al. 2015, for recent results and reviews).”
• Detection of high Lyman continuum leakage from four low-redshift compact star-forming galaxies (2016, background): “…the bulk of the ionizing radiation, since the observed UV luminosity function is very steep at high-z and hence faint galaxies are very numerous (Ouchi et al. 2009; Wise & Chen 2009; Mitra, Ferrara & Choudhury 2013; Yajima, Choi & Nagamine 2011; Bouwens et al. 2015a). c© 2012 RAS ar X iv :1 60 5.”