The Abundance of Star-Forming Galaxies in the Redshift Range 8.5-12: New Results From the 2012 Hubble Ultra Deep Field Campaign

We investigate constraints on cosmic reionization extracted from the Planck cosmic microwave background (CMB) data. We combine the Planck CMB anisotropy data in temperature with the low-multipole polarization data to fit ΛCDM models with various parameterizations of the reionization history. We obtain a Thomson optical depth τ = 0.058±0.012 for the commonly adopted instantaneous reionization model. This confirms, with data solely from CMB anisotropies, the low value suggested by combining Planck 2015 results with other data sets, and also reduces the uncertainties. We reconstruct the history of the ionization fraction using either a symmetric or an asymmetric model for the transition between the neutral and ionized phases. To determine better constraints on the duration of the reionization process, we also make use of measurements of the amplitude of the kinetic Sunyaev-Zeldovich (kSZ) effect using additional information from the high-resolution Atacama Cosmology Telescope and South Pole Telescope experiments. The average redshift at which reionization occurs is found to lie between z = 7.8 and 8.8, depending on the model of reionization adopted. Using kSZ constraints and a redshift-symmetric reionization model, we find an upper limit to the width of the reionization period of ∆z < 2.8. In all cases, we find that the Universe is ionized at less than the 10% level at redshifts above z 10. This suggests that an early onset of reionization is strongly disfavoured by the Planck data. We show that this result also reduces the tension between CMB-based analyses and constraints from other astrophysical sources.

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“…have existed at z > ∼ 11 (e.g., Kuhlen & Faucher-Giguère 2012;Ellis et al 2013;Cai et al 2014;Ishigaki et al 2015).…”

Section: Discussionmentioning

confidence: 99%

Planckintermediate results

Adam

Aghanim

Ashdown

et al. 2016

A&A

385

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“…For the sub-set of galaxies in the central 2 ′ ×2 ′ region of HUDF (corresponding to the WFC3 field of view), we also generated a third mass map making use of the extremely deep observations available at all wavelengths: the optical HUDF images and the HST /WFC3 F105W, F125W, F140W and F160W coverage from the HUDF09 and HUDF12 surveys (Bouwens et al 2011;Ellis et al 2013). We specifically employed the mosaics provided by the HUDF12 team which are combined with the HUDF09 datasets.…”

Section: Archival Hst Observationsmentioning

confidence: 99%

A PHYSICAL APPROACH TO THE IDENTIFICATION OF HIGH-ZMERGERS: MORPHOLOGICAL CLASSIFICATION IN THE STELLAR MASS DOMAIN

Cibinel

Floc’h

Perret

et al. 2015

ApJ

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At z 1, the distinction between merging and "normal" star-forming galaxies based on single band morphology is often hampered by the presence of large clumps which result in a disturbed, merger-like appearance even in rotationally supported disks. In this paper we discuss how a classification based on canonical, non-parametric structural indices measured on resolved stellar mass maps, rather than on single-band images, reduces the misclassification of clumpy but not merging galaxies. We calibrate the mass-based selection of mergers using the MIRAGE hydrodynamical numerical simulations of isolated and merging galaxies which span a stellar mass range of 10 9.8 -10 10.6 M ⊙ and merger ratios between 1:1-1:6.3. These simulations are processed to reproduce the typical depth and spatial resolution of observed Hubble Ultra Deep Field (HUDF) data. We test our approach on a sample of real z ≃ 2 galaxies with kinematic classification into disks or mergers and on ∼100 galaxies in the HUDF field with photometric/spectroscopic redshift between 1.5 z 3 and M > 10 9.4 M ⊙ . We find that a combination of the asymmetry A MASS and M 20,MASS indices measured on the stellar mass maps can efficiently identify real (major) mergers with 20% contamination from clumpy disks in the merger sample. This mass-based classification cannot be reproduced in star-forming galaxies by H−band measurements alone, which instead result in a contamination from clumpy galaxies that can be as high as 50%. Moreover, we find that the mass-based classification always results in a lower contamination from clumpy galaxies than an H−band classification, regardless of the depth of the imaging used (e.g.,

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“…On the other hand, a huge amount of spectroscopic data are available in Lyα, up to the reionisation redshift (e.g. Shapley et al 2003;Hu et al 2010;Stark et al 2010;Guaita et al 2010Guaita et al , 2011Dressler et al 2011;Bielby et al 2011;Pentericci et al 2010Pentericci et al , 2011Kulas et al 2012;Jiang et al 2013b,a;Ellis et al 2013;Schenker et al 2013). Could we tell from the Lyα line shape if a galaxy is a good candidate for continuum leaking?…”

Section: Introductionmentioning

confidence: 99%

Using Lyman-αto detect galaxies that leak Lyman continuum

Verhamme

Orlitová

Schaerer

et al. 2015

A&A

302

439

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Aims. We propose to infer the output of the ionising continuum-leaking properties of galaxies based upon their Lyα line profiles. Methods. We carried out Lyα radiation transfer calculations in two models of H ii regions. These models are porous to ionising continuum escape: 1) we define Lyman-continuum (LyC) optically thin star clusters, in which massive stars produce enough ionising photons to keep the surrounding interstellar medium transparent to the ionising continuum, in other words, almost totally ionised; and 2) we define riddled ionisation-bounded media that are surrounded by neutral interstellar medium, but have holes, which results in a covering fraction lower than unity. Results. The Lyα spectra that emerge from these configurations have distinctive features: 1) a classical asymmetric redshifted profile in the first case, but with a small shift of the profile maximum compared to the systemic redshift (v peak ≤ 150 km s −1 ); 2) a main peak at the systemic redshift in the second case (v peak = 0), with a non-zero Lyα flux bluewards of the systemic redshift as a consequence. If in a galaxy that leaks ionising photons the Lyα component that emerges from the leaking star cluster(s) is assumed to dominate the total Lyα spectrum, the Lyα shape may be used as a pre-selection tool for detecting LyC-leaking galaxies in objects with high spectral resolution Lyα spectra (R ≥ 4000). Our predictions are corroborated by examination of a sample of ten local starbursts with high-resolution HST/COS Lyα spectra that are known in the literature as LyC leakers or leaking candidates. Conclusions. Observations of Lyα profiles at high resolution are expected to show definite signatures revealing the escape of Lyman-continuum photons from star-forming galaxies.

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The Abundance of Star-Forming Galaxies in the Redshift Range 8.5-12: New Results From the 2012 Hubble Ultra Deep Field Campaign

Cited by 463 publications

References 36 publications

Planckintermediate results

Planckintermediate results

A PHYSICAL APPROACH TO THE IDENTIFICATION OF HIGH-ZMERGERS: MORPHOLOGICAL CLASSIFICATION IN THE STELLAR MASS DOMAIN

Using Lyman-αto detect galaxies that leak Lyman continuum

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