The redshift evolution of escape fraction of hydrogen ionizing photons from galaxies

Khaire, Vikram; Srianand, R.; Choudhury, Tirthankar Roy; Gaikwad, Prakash

doi:10.1093/mnras/stw192

Cited by 123 publications

(150 citation statements)

References 141 publications

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“…Furthermore, we assume fesc = 0.2, which is consistent with the value used by Raičević et al (2011). Sharma et al (2016) present observational and theoretical evidence in support of this choice of fesc (see also Khaire et al 2016). The microwave background data measure the optical depth to the time when the Universe (re)combined.…”

Section: Redshift Of Reionisationsupporting

confidence: 71%

“…On the smallest scales, SNfb, in conjunction with photoionisation of gas in the early Universe, can explain the small number of faint satellite galaxies seen around galaxies like the Milky Way in this model (Efstathiou 1992;Benson et al 2003;Sawala et al 2015). Unless AGN contribute a significant number of ionising photons (Madau & Haardt 2015;Khaire et al 2016), SNfb cannot be so strong as to suppress the production of ionising photons at high redshift required to reionise the Universe by z ∼ 6, as inferred from QSO absorption lines (Mitra et al 2015;Robertson et al 2015) and the microwave background data (Ade et al 2015). Thus, at least in CDM, the small observed number of faint galaxies sets a lower limit to the strength of feedback, while the requirement that the Universe be ionised early enough sets an upper limit.…”

Section: A Galactic "Tug-of-war"mentioning

confidence: 99%

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Reionization in sterile neutrino cosmologies

Bose¹,

Frenk²,

Hou³

et al. 2016

Mon. Not. R. Astron. Soc.

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTWe investigate the process of reionisation in a model in which the dark matter is a warm elementary particle such as a sterile neutrino. We focus on models that are consistent with the dark matter decay interpretation of the recently detected line at 3.5 keV in the X-ray spectra of galaxies and clusters. In warm dark matter models the primordial spectrum of density perturbations has a cut-off on the scale of dwarf galaxies. Structure formation therefore begins later than in the standard cold dark matter (CDM) model and very few objects form below the cut-off mass scale. To calculate the number of ionising photons, we use the Durham semianalytic model of galaxy formation, GALFORM. We find that even the most extreme 7 keV sterile neutrino we consider is able to reionise the Universe early enough to be compatible with the bounds on the epoch of reionisation from Planck. This, perhaps surprising, result arises from the rapid build-up of high redshift galaxies in the sterile neutrino models which is also reflected in a faster evolution of their far-UV luminosity function between 10 > z > 7 than in CDM. The dominant sources of ionising photons are systematically more massive in the sterile neutrino models than in CDM. As a consistency check on the models, we calculate the present-day luminosity function of satellites of Milky Way-like galaxies. When the satellites recently discovered in the DES survey are taken into account, strong constraints are placed on viable sterile neutrino models.

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Section: Redshift Of Reionisationsupporting

confidence: 71%

Section: A Galactic "Tug-of-war"mentioning

confidence: 99%

Reionization in sterile neutrino cosmologies

Bose¹,

Frenk²,

Hou³

et al. 2016

Mon. Not. R. Astron. Soc.

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“…They show, through the Gunn-Peterson effect, that the diffuse gas in the Universe is mostly ionized up to a redshift of about 6 (Fan et al 2006a). Given the decline in their abundance beyond redshift z 6, quasars and other active galactic nuclei (AGN) cannot be major contributors to the early stages of reionization (e.g., Willott et al 2010;Fontanot et al 2012, but see Madau & Haardt 2015Khaire et al 2016, for alternative AGN-only models). A faint AGN population can produce significant photoionization rates at redshifts of 4-6.5, consistent with the observed highly ionized IGM in the Ly-α forest of high-z quasar spectra (Giallongo et al 2015).…”

Section: Discussionmentioning

confidence: 99%

Planckintermediate results

Adam

Aghanim

Ashdown

et al. 2016

A&A

405

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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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“…Ferrara & Loeb 2013;Kimm & Cen 2014;Mitra et al 2013). Depending on the exact model used, its value either shows an increase (Gnedin et al 2008;Wise & Cen 2009) or decrease (Razoumov & SommerLarsen 2010;Ferrara & Loeb 2013;Wise et al 2014;Paardekooper et al 2015) with halo mass or solely depends on redshift (Khaire et al 2016, and references within). In addition, (infrared) observations provide only weak constraints that are limited to galaxies at z 3 − 4 (Cooke et al 2014;Vanzella et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Exploring 21 cm-Lyα Emitter Synergies for SKA

Hutter

Dayal

Müller

et al. 2017

ApJ

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We study the signatures of reionization and ionizing properties of the early galaxies in the cross-correlations between the 21cm emission from the spin-flip transition of neutral hydrogen (H I ) and the underlying galaxy population, in particular a sub-population of galaxies visible as Lyman Alpha Emitters (LAEs). With both observables simultaneously derived from a z 6.6 hydrodynamical simulation (GADGET-2) snapshot post-processed with a radiative transfer code (pCRASH) and a dust model, we perform a parameter study and aim to constrain both the average intergalactic medium (IGM) ionization state (1 − χ HI ) and the reionization topology (outside-in versus inside-out). We find that in our model LAEs occupy the densest and most-ionized regions resulting in a very strong anti-correlation between the LAEs and the 21cm emission. A 1000 h SKA-LOW1 -Subaru Hyper Suprime Cam experiment can provide constraints on χ HI , allowing us to distinguish between IGM ionization levels of 50%, 25%, 10% and fully ionized at scales r < ∼ 10 comoving Mpc (assuming foreground avoidance for SKA). Our results support the inside-out reionization scenario where the densest knots (under-dense voids) are ionized first (last) for χ HI > ∼ 0.1. Further, 1000 h SKA-LOW1 observations should be able to confirm the inside-out scenario by detecting a lower 21cm brightness temperature (by about 2-10 mK) in the densest regions ( > ∼ 2 arcminute scales) hosting LAEs compared to lower-density regions devoid of them.

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The redshift evolution of escape fraction of hydrogen ionizing photons from galaxies

Cited by 123 publications

References 141 publications

Reionization in sterile neutrino cosmologies

Reionization in sterile neutrino cosmologies

Planckintermediate results

Exploring 21 cm-Lyα Emitter Synergies for SKA

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