RADIATIVE TRANSFER IN A CLUMPY UNIVERSE WITH CUBA

PIERO MADAUUC SANTA CRUZ

RADIATIVE TRANSFER IN A CLUMPY UNIVERSE WITH CUBA

Friday, July 29, 2011

UV radiation from stars and accreting MBHs keeps the universe ionized, shapes the IGM, and regulates gas cooling and star formation in galaxies.

The integrated UVB traces the rise and fall of the quasar population, the cosmic history of star formation in galaxies, the evolving escape fraction into intergalactic space of UV radiation, and its reprocessing by an expanding clumpy IGM.

The UVB remains a crucial yet most uncertain input parameters for cosmological simulations of LSS and galaxy formation and for interpreting QSO absorption lines observations.


HOME DOWNLOADS BIBLIOGRAPHY ABOUT US

CUBA is a radiative transfer code that follows the propagation of hydrogen and

helium Lyman continuum radiation through a partially ionized and clumpy

intergalactic medium. The only sources of ionizing radiation included in CUBA

are star-forming galaxies and quasars.

Contador

CUBACosmic Ultraviolet BAckground

a cosmological 1D radiative transfer code by

Francesco Haardt and Piero Madau

www.ucolick.org/~pmadau/CUBA


http://www.ucolick.org/~pmadau/CUBA

http://www.ucolick.org/~pmadau/CUBA

The equation of cosmological radiative transfer describes the timeevolution of the space- and angle-averaged monochromatic intensity Jν:

Cosmological radiative transfer

RT equation must be solved by iterations since


➔ Poissonian probability of encountering a total optical depth kτ0 is:

Assume random distribution of absorbers in column density and redshift space, then:

Effective optical depth of the IGM

observed must be modeled


Lyαforest

z=2

z=3.5

z=5

LLS

SLLS

DLA

Prochaska et al. 2009

Quasar absorbers along the LOS


Cowie et al. 2009

Hopkins et al. 2007Bongiorno et al. 2007

Meiksin 2005

10 keV

2 keV

Intrinsic HXLF: Ueda et al. 2003Silverman et al. 2008

SXLF after absorption: PM et al. 1994

The X-ray properties of the quasar population as a whole are recorded in the cosmic XRB: 1) XRB may play a unique role in regulating the thermodynamics and ionization degree of intergalactic absorbers; 2) Soft X-rays between 0.5 and 0.9 keV are responsible for the highest ionization states of C, N, O; 3) X-rays penetrate regions that are optically thick to UV radiation, providing a source of heating and ionization; 4) Compton scattering of hard XRB photons may be a source of heating for highly ionized low-density intergalactic gas.

QSO emissivity

Type I and II QSOs

SAX

HEAO-1A2 HED

HEAO-1A4 LED

HEAO-1

A4 MED

ROSAT

XMM

XMM

XTE


Galaxy emissivity

Schiminovich et al 2005 Reddy & Steidel 2009 Bouwens et al 2010

Calzetti et al. 2000

Kewley & Kobulnicky 2007

Rate of H-ionizing photons vs time for SSP

GALEXEVSTARBURST99

FSPSall Salpeter IMF

Z=Z⊙

GALEXEV Z=0.2Z⊙

z=0 EBL


Kuhlen et al 2011Dwarf galaxy formation with H2-regulated SF


QSOs

Galaxies

Escape fraction

Inoue et al. 2006

Bolton & Haehnelt 07Becker et al. 07

Faucher-Giguere et al. 08Calverley et al 10


1) Absorbers are not only sinks but also sources of ionizing radiation: recombinations to ground states of HI, HeI, HeII, HeII Balmer and 2γ-continuum, HeII Lyα

Two important effects

J

x

J

!

0 L

Solve numerically (local radiative transfer) for the photoionization structure of individual absorbers (semi-infinite slab with L=λJ)


2) besides photoelectric absorption, resonant absorption by H and He Lyman series will produce a sawtooth modulation of the UVB spectrum.

Lyβ

Lyγ

PM & Haardt 2009Haiman et al. 1997Pritchard & Furlanetto 2006

OII SiIV CIII OIII


HI distribution

cosmological radiative transfer ➔ J

τeff, εrec

QSO/GAL LF SED

J-solution flow chart

ABSORBERS SOURCES

local radiative transfer ➔H/He ionization state


Building up the UVB (Gal+QSOs) @ z=3


UVB: quasars only

HM96

HM11


UVB: quasars + galaxies

QSO

Gal+QSO

Gal SED steeper than QSO ➔ HeII/HI↑


HeII sawtooth

QSO

Gal+QSO


HI sawtooth

Gal+QSO


Reionization @ milliFLOP speed (PM, Haardt, & Rees 1999; Shapiro & Giroux 1987)

QI(t)= volume filling factor of HII regions at t

The reionization equation

QI(t) =! t

0n!(t!)

!nH(t!)"dt# !! t

0QI (t!)

trecdt#

source sink

(no redshifting, ionizing photons assorbed locally). Differentiating:

dQI

dt=

n!

!nH" !QI

trec

simple diff. eq. statistically describes transition from a neutral Universe to a

fully ionized one!Contrary to the static case, cosmological HII regions will always percolate in an expanding universe with constant comoving ionizing emissivity....


A “minimal reionization model” We have integrated the

reionization equation assuming T=104.3 K and gas clumping

factor CIGM=1+43/z1.71

CIGM=3 @ z=6

NO POPIII !CIGM≡C100 from Pawlik et al. 2009

CHeIII≡CIGM

Reionization is extended


τe(0,z)x10

Optical depth for e- scattering

WMAP-7 τe=0.088±0.015


THE END


Documents

RADIATIVE TRANSFER IN A CLUMPY UNIVERSE WITH CUBA