A Census of the LyC photons that form the UV background during reionization

Harley Katz, Taysun Kimm, Martin Haehnelt, Debora Sijacki, Joakim Rosdahl, Jeremy Blaizot

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

We present a new, on-the-fly photon flux and absorption tracer algorithm designed to directly measure the contribution of different source populations to the metagalactic ultraviolet (UV) background and to the ionization fraction of gas in the Universe. We use a suite of multifrequency radiation hydrodynamics simulations that are carefully calibrated to reproduce a realistic reionization history and galaxy properties at z ≥ 6, to disentangle the contribution of photons emitted by different mass haloes and by starswith different metallicities and ages to the UV background during reionization. While at very early cosmic times low-mass, metal-poor haloes provide most of the Lyman continuum photons, their contribution decreases steadily with time. At z = 6 it is the photons emitted by massive systems (M halo /M > 10 10 h -1 ) and by the metal enriched stars (10 -3 < Z/Z < 10 -1.5 ) that provide the largest contribution to the ionising UV background. We demonstrate that there are large variations in the escape fraction depending on the source, with the escape fraction being highest (~45-60 per cent) for photons emitted by the oldest stars that penetrate into the intergalactic medium via low opacity channels carved by the ionising photons and supernova from younger stars. Before HII regions begin to overlap, the photoionization rate strongly fluctuates between different, isolated HII bubbles, depending on the embedded ionising source, which we suggest may result in spatial variations in the properties of dwarf galaxies.

Original languageEnglish
Pages (from-to)4986-5005
Number of pages20
JournalMonthly Notices of the Royal Astronomical Society
Volume478
Issue number4
DOIs
Publication statusPublished - 2018 Aug 21

Fingerprint

census
metal
photons
bubble
halos
ionization
spatial variation
hydrodynamics
tracer
stars
escape
history
gas
simulation
intergalactic media
dwarf galaxies
opacity
metals
metallicity
tracers

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Katz, Harley ; Kimm, Taysun ; Haehnelt, Martin ; Sijacki, Debora ; Rosdahl, Joakim ; Blaizot, Jeremy. / A Census of the LyC photons that form the UV background during reionization. In: Monthly Notices of the Royal Astronomical Society. 2018 ; Vol. 478, No. 4. pp. 4986-5005.
@article{d8c7b74ce2c64606a537feccb59cdfa3,
title = "A Census of the LyC photons that form the UV background during reionization",
abstract = "We present a new, on-the-fly photon flux and absorption tracer algorithm designed to directly measure the contribution of different source populations to the metagalactic ultraviolet (UV) background and to the ionization fraction of gas in the Universe. We use a suite of multifrequency radiation hydrodynamics simulations that are carefully calibrated to reproduce a realistic reionization history and galaxy properties at z ≥ 6, to disentangle the contribution of photons emitted by different mass haloes and by starswith different metallicities and ages to the UV background during reionization. While at very early cosmic times low-mass, metal-poor haloes provide most of the Lyman continuum photons, their contribution decreases steadily with time. At z = 6 it is the photons emitted by massive systems (M halo /M ⊙ > 10 10 h -1 ) and by the metal enriched stars (10 -3 < Z/Z ⊙ < 10 -1.5 ) that provide the largest contribution to the ionising UV background. We demonstrate that there are large variations in the escape fraction depending on the source, with the escape fraction being highest (~45-60 per cent) for photons emitted by the oldest stars that penetrate into the intergalactic medium via low opacity channels carved by the ionising photons and supernova from younger stars. Before HII regions begin to overlap, the photoionization rate strongly fluctuates between different, isolated HII bubbles, depending on the embedded ionising source, which we suggest may result in spatial variations in the properties of dwarf galaxies.",
author = "Harley Katz and Taysun Kimm and Martin Haehnelt and Debora Sijacki and Joakim Rosdahl and Jeremy Blaizot",
year = "2018",
month = "8",
day = "21",
doi = "10.1093/mnras/sty1225",
language = "English",
volume = "478",
pages = "4986--5005",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "4",

}

A Census of the LyC photons that form the UV background during reionization. / Katz, Harley; Kimm, Taysun; Haehnelt, Martin; Sijacki, Debora; Rosdahl, Joakim; Blaizot, Jeremy.

In: Monthly Notices of the Royal Astronomical Society, Vol. 478, No. 4, 21.08.2018, p. 4986-5005.

Research output: Contribution to journalArticle

TY - JOUR

T1 - A Census of the LyC photons that form the UV background during reionization

AU - Katz, Harley

AU - Kimm, Taysun

AU - Haehnelt, Martin

AU - Sijacki, Debora

AU - Rosdahl, Joakim

AU - Blaizot, Jeremy

PY - 2018/8/21

Y1 - 2018/8/21

N2 - We present a new, on-the-fly photon flux and absorption tracer algorithm designed to directly measure the contribution of different source populations to the metagalactic ultraviolet (UV) background and to the ionization fraction of gas in the Universe. We use a suite of multifrequency radiation hydrodynamics simulations that are carefully calibrated to reproduce a realistic reionization history and galaxy properties at z ≥ 6, to disentangle the contribution of photons emitted by different mass haloes and by starswith different metallicities and ages to the UV background during reionization. While at very early cosmic times low-mass, metal-poor haloes provide most of the Lyman continuum photons, their contribution decreases steadily with time. At z = 6 it is the photons emitted by massive systems (M halo /M ⊙ > 10 10 h -1 ) and by the metal enriched stars (10 -3 < Z/Z ⊙ < 10 -1.5 ) that provide the largest contribution to the ionising UV background. We demonstrate that there are large variations in the escape fraction depending on the source, with the escape fraction being highest (~45-60 per cent) for photons emitted by the oldest stars that penetrate into the intergalactic medium via low opacity channels carved by the ionising photons and supernova from younger stars. Before HII regions begin to overlap, the photoionization rate strongly fluctuates between different, isolated HII bubbles, depending on the embedded ionising source, which we suggest may result in spatial variations in the properties of dwarf galaxies.

AB - We present a new, on-the-fly photon flux and absorption tracer algorithm designed to directly measure the contribution of different source populations to the metagalactic ultraviolet (UV) background and to the ionization fraction of gas in the Universe. We use a suite of multifrequency radiation hydrodynamics simulations that are carefully calibrated to reproduce a realistic reionization history and galaxy properties at z ≥ 6, to disentangle the contribution of photons emitted by different mass haloes and by starswith different metallicities and ages to the UV background during reionization. While at very early cosmic times low-mass, metal-poor haloes provide most of the Lyman continuum photons, their contribution decreases steadily with time. At z = 6 it is the photons emitted by massive systems (M halo /M ⊙ > 10 10 h -1 ) and by the metal enriched stars (10 -3 < Z/Z ⊙ < 10 -1.5 ) that provide the largest contribution to the ionising UV background. We demonstrate that there are large variations in the escape fraction depending on the source, with the escape fraction being highest (~45-60 per cent) for photons emitted by the oldest stars that penetrate into the intergalactic medium via low opacity channels carved by the ionising photons and supernova from younger stars. Before HII regions begin to overlap, the photoionization rate strongly fluctuates between different, isolated HII bubbles, depending on the embedded ionising source, which we suggest may result in spatial variations in the properties of dwarf galaxies.

UR - http://www.scopus.com/inward/record.url?scp=85050792605&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85050792605&partnerID=8YFLogxK

U2 - 10.1093/mnras/sty1225

DO - 10.1093/mnras/sty1225

M3 - Article

VL - 478

SP - 4986

EP - 5005

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 4

ER -