DLAs, Escape Fraction, & RT Ken Nagamine UNLV Collaborators: - - PowerPoint PPT Presentation

Ken Nagamine UNLV

Collaborators: Hidenobu Yajima (Penn State) Jun-Hwan Choi (Kentucky) Robert Thompson, Jason Jaacks (UNLV)

DLAs, Escape Fraction, & RT

KN, Choi, Yajima, 2010, ApJ, 725, L219 Yajima, Choi, KN, 2011, MN, 412, 411 Yajima, Choi, KN, 2012, MN, in press Thompson, KN+ ’12, in prep.

Outline

• Introduction
• DLAs, Column Density Distribution: f(NHI)
• What physical processes shape f(NHI)?
• - effects of radiation (stellar, UVB) & feedback
• How big are DLAs? -- Cross section σDLA(Mh)
• Escape Fraction of ionizing photons
• Conclusions

NHI > 2 × 1020 cm−2

☀ quasar

DLAs are heavy-weight champions of HI absorbers

(Wolfe+ ‘86)

Direct probe of HI gas in high-z universe

What are DLAs?

Need to understand these systems in the context of CDM model

Gallery of DLAs

Pontzen+ ’08

Cen ’10

Razoumov+ ’06

NHI

DLA

KN+ ‘04a,b

proper 200 kpc

Fumagalli+ ’11

proper 200 kpc

Hong+ ’10

Tescari+’09

Yajima+ ’12

NHI

DLAs

M★

SFR

MZ

Metallicity

~100kpc phys

KN04a,b

z=3

UVB

local stellar radiation

Column density distribution f(NHI)

z=3

• No-feedback run
• verpredicts at high NHI.
• Strong feedback suppresses

the high NHI-end. (SH03 SF

model)

• But under-estimate at

NHI<~21 dex

• Assumed optically-thin UVB

KN+ ‘04a,b

Effect of UVB on f(NHI)

• No-UVB run overpredicts.
• UVB sinks in too much

w/ opt-thin approx.

• Shutting off UVB at

ρ>0.01ρth,SF yields good result. ρthUV ~10-3-10-2 cm-3

(cf. Tajiri & Umemura ’98; Kollmeier+ ’09)

KN+ ’10

no-UVB

OTUV (opt-thin)

• pt-thin

Effects of UVB and Self-Shielding

nsf ~ 0.6 cm-3 nuv ~ 6e-3 cm-3

Opt-thin approx. OTUV model

nuv nsf nsf nuv

Neutral fraction T emperature

Gas density Gas density

KN+ ’10

Important for DLA gas!

ART method

Authentic Ray Tracing Method

! ! !

" # + $ = I ds dI

abs

!"adiation meshes are arranged radially from each sources independently of fluid meshes. !#he radiation field on fluid meshes are estimated by interpolating from near radiation meshes. !#he order of calculation amount

Nsource " N# " N$ " N path

Nsource " Nx " Ny " Nz " N path

Long characteristic method:

Basic equation:

(Nakamoto et al. 2001, Iliev et al. 2006)

(from Yajima, ’09)

Validating OTUV model w/ RT calculation

Neutral fraction

Mtot=2e12 M⦿

gas density

nuv ~ 6e-3 cm-3

OTUV:

Yajima, Choi, KN ’12

red: UVB RT + collis. ioniz. + stellar RT magenta: UVB RT + collis. ioniz. green: UVB RT

gas density

Γγ

star = ˙

Nph0 exp(−)/42

= 0nHI

Validating OTUV model w/ RT calculation

Neutral fraction

Mtot=2e12 M⦿

gas density

nuv ~ 6e-3 cm-3

OTUV:

Yajima, Choi, KN ’12

red: UVB RT + collis. ioniz. + stellar RT magenta: UVB RT + collis. ioniz. green: UVB RT

Altay+ ’11

Rahmati+ ’12 Faucher-Giguere+ ’10

Effects of Local Stellar Radiation on DLAs

KN+ ’10

Yajima+ ’12

• pen circle --

before RT (OTUV) red & magenta points -- after stellar RT

slight reduction in σ by stellar RT

f(NHI) is not so much affected by stellar rad RT

Effects of Radiation on NHI

Halo A

Mh=7e11 M⦿ L=300 kpc

Halo B

Mh=3e10 M⦿ L=80 kpc

no RT

UVB RT + coll. ioniz. UVB+coll. ioniz.+star RT

Yajima+ ’12

UVB+coll. ioniz.+star RT Opt-thin approx.

Halo A

Mh=7e11 M⦿ L=300 kpc

Mh=1e11 M⦿ L=159 kpc

Halo Halo Halo Halo

Stellar mass NHI

Metallicity

Yajima, Choi, KN ’12

(Circles: physical Rvir = 68, 37, 23, 11 kpc)

DLA Cross Section vs. Halo Mass

Yajima, Choi, KN ’12

T escari+ ’09; GADGET SPH Fumagali+ ’11; ART AMR Pontzen+ ’08; GASOLINE SPH Cen ’10; Enzo AMR

Effect of H2 on f(NH)

Thompson, KN+ ’12

Altay+ ’11 Rahmati+ ’12

F . 11.— E ect on column density distribution of removing

Erkal+ ’12

Cosmology (Ωb, σ8), SF, FB, UVB, H2, ….

Escape Fraction

Log XHI

• 2
• 4
• 6

216 kpc 48 kpc

Halo A Halo B

Yajima, Choi, KN ’11

Choi & KN ’09 cosmo SPH sims

fesc ~ few %

fesc ~ few 10s%

Authentic Ray Tracing method

(Nakamoto+ ’01, Illiev+ ’06, Yajima+ ’09)

Mtot ∼ 7 × 1011 M

Mtot ∼ 1 × 1010 M

• Choi & KN ’09 cosmo

SPH sims w/ MVV wind feedback models

• Decreasing fesc as a

func of Mhalo --- roughly consistent with Razoumov+’09; but different from Gnedin +’09, Wise & Cen ’09

Yajima, Choi, KN ’11

fesc as a function of Mhalo & redshift

Escape Fraction of Ionizing Photons

Authors

fesc,ion (Mhalo)

Method

Gnedin+ ’09

10-5-10-1,

AMR, 6Mpc box, 65pc res, OTVET, z=3

Razoumov+’09

1.0-0.0,

SPH, 6Mpc box, ~0.5kpc res, resim 9 gals, z=4-10

Wise & Cen +’09 0-0.4,

AMR, 2 & 8Mpc box, 0.1pc res, z=8

Yajima+ ’09

0-0.5,

Eulerian (Mori &

Umemura ’06 sim, single

system, t=0-1Gyr)

Yajima, Choi, KN ’11 1.0-0.0

SPH, 10Mpc box, ~0.5kpc res, z=3-6 100s of gals. 1011-1012 M⦿

Very low

108-1011M⦿ 106-109M⦿

Large scatter & time evol.

with time

10

• 5

10

• 4

SFR [MO

• yr
• 1]

(1) Mvir = 1.57 x 10

• 20

40 60 80 100

Time [Myr]

10

• 3

10

• 2

10

• 1

10

fesc

• 1

109-1012M⦿

• Fig. 13.

Paardekooper+ ’11

Reionization of the Universe

• Simulations suggest

that the Universe can be reionized by the star-forming galaxies at z=6 if C≤10.

• High fesc for low-mass

gals helps.

• Dashed line: possible

quasar contribution

• Dotted line: Bolton &

Haehnelt ’07

Blue points: intrinsic emission rate density Red points: escaped photons Yajima, Choi, KN ’11

Reionization of the Universe

• Starforming gals can reionize

the Universe by z=6.

• Showing contribution from
• diff. gal. mass ranges
• yellow & cyan shade: results

from Munoz & Loeb ’11

• dotted line: required SFRD

based on Madau ’99:

˙ ρ ≈ 2 × 10−3 C fesc 1 + z 10 3

<fesc>=0.42 from RT result of Yajima+ ’11

Jaacks, Choi, KN ’12

Impact of H2-based SF model

Thompson, KN+ ’12

Implementation of Krumholz+ ’08, ’09 H2 models into cosmo sims

Conclusions

• Shape of f(NHI): not fully understood yet --

Very rich subject

• DLA cross section: σDLA≈103 kpc2 for Mh=1012 M⦿
• -- but slope and shape of σ(Mh); more study needed.
• Opt-thin approx is no good; the OTUV model is a good
• approx. to the RT result. (KN+ ’10;

Yajima+ ’12)

• fesc: wide variety; not understood. Scatter and time

variation

• Future work: Improve SF and feedback (SN/AGN); H2

effect; Metallicity & radiation dependence (metal diffusion; turbulence…)

End