Radiative Transfer Simulations

The Proximity Effect of LBGs:

Antonella Maselli, OAArcetri, Firenze, Italy

Collaborators: A.Ferrara, M. Bruscoli, S. Marri & R. SchneiderMarri et al 2003, in preparationBruscoli et al, 2003,MNRAS,343,L45Maselli et al, 2003,submitted to MNRAS

Japan - Italy Joint Seminar, 2003

Theoretical Expectations

The physical properties of IGM close to galaxies can be studied through the statistics of absorption lines associated with foreground galaxies in QSOs spectra

Predictions:

• HIGHER NUMBER OF STRONG Ly ABSORPTION LINES• LOWER MEAN Ly TRANSMITTED FLUX at smaller l.o.s./galaxy impact parameters

• 8 bright QSOs at 3.1< z <4.1

• 431 Lyman Break Galaxies at z3

OBSERVATIONS: Results

Adelberger et al (2002)

• LBGs are associated with HI

overdensities at scales 1 Mpc < r < 7 Mpc

• LBGs are associated with HI

underdensities at scales < 1Mpc

• 8 bright QSOs at 3.1< z <4.1

• 431 Lyman Break Galaxies at z3

OBSERVATIONS: Results

Adelberger et al (2002)

Interpretations for the transparency of the inner

region

• Observations are biased

• SNe Driven-Winds

• Local Photoionization

Numerical Simulations: WINDS

WINDSUVB (Haardt & Madau 1996)

z =3.26

LBOX = 10.5 Mpc h-1 comoving

Multiphase SPH simulation(Marri et al., 2003; Marri & White, 2002)

consistent withCroft et al (2002)

Kollmeier et al (2003)

Bruscoli et al (2002)

398 galaxies identified with a HOP group finding algorithm (Eisenstein & Hut, 1998)

OUTFLOWS CANNOTCLEAR THE GAS AROUND GALAXIES

AS REQUIRED BY OBSERVATIONS

COMMON ASSUMPTION:

PHOTONS ESCAPING FROM LBGs HAVE A MEAN FREE PATH EQUAL TO THAT IN THE IGM

240 Mpc h-1

LOCAL PHOTOIONIZATION?can do the job?

Croft et al (2002)

Kollmeier et al (2003)

Adelberger et al (2003) Analytical approach

Numerical approach

}Negative answer

THE IGM IN THE VICINITY OF GALAXIES HAS BIASED PHYSICALPROPERTIES

FULL CONSISTENT RADIATIVE TRANSFER SIMULATIONS ARE NEEDED TO ANSWER THE QUESTION

Japan - Italy Joint Seminar, 2003

Sphere of influence of a typical galaxy

Local photoionization can be significant in determining the ionization state of the

IGM where : Fgal/F bkg > 1

V(Fgal/F bkg > 1) 5 % Vbox

Rinfluence 0.4 Mpc h-1 for a typical galaxy

in the simulation

Japan - Italy Joint Seminar, 2003

+Ionizing sources

• Multiple point sources• Background (UVB)• Diffuse radiation from recombinations

Radiative Transfer Simulations: CRASH Maselli et al (2003)

Arbitrary 3-D precomputed cosmological H/He density field

Multiphase SPH simulation

3-D gas distribution (nH, T, xI)

398 galaxies (L SFR , Starbust99 )

UVB, (Haardt & Madau 1996)

Time evolution of TEMPERATURE

and IONIZATION FRACTIONS

inside the simulation volume

OUTPUTS

Japan - Italy Joint Seminar, 2003

Neutral Hydrogen Fraction

90 M yr -1SFR 0.09 M yr -1

290 M yr -1

9.2 x 108 M

8.7 x 1010 M

Less massive galaxy

NO galaxy

4 M

pc h

-14

Mpc

h-1

NO galaxy SFR 29 M yr -1

Most massive galaxy

Japan - Italy Joint Seminar, 2003

Neutral Hydrogen Fraction

SFR 90 M yr -1

SFR 29 M yr -1

SFR 0.09 M yr -1

SFR 290 M yr -1

9.2 x 108 M

8.7 x 1010 M

Most massive galaxy

Less massive galaxy

NO galaxy

NO galaxy

4 M

pc h

-14

Mpc

h-1

Japan - Italy Joint Seminar, 2003

Neutral Hydrogen Fraction along LOS across galaxies

SFR 290 M yr -1

Log

(x H

I) UVB

SFR from SPHSFR boosted

along x along y along z

1 Mpc h-1 comoving

SFR 29 M yr -1

8.7 x 1010 M

SFR 0.09 M yr -1 SFR 90 M yr-1 lowest mass galaxy

highest mass galaxy

9.2 x 108 M

Japan - Italy Joint Seminar, 2003

Mean Ly Transmitted Flux: UVB & Galaxies

<F> mean Flux Ly trasmissivity r los/galaxy separation for 398 galaxies

The UV emission by galaxies has little effect on

the mean Ly trasmissivity of the IGM

Japan - Italy Joint Seminar, 2003

<F> mean Flux Ly trasmissivity r los/galaxy separation for 9 galaxies with M > 2 x 1010 M

Mean Ly Transmitted Flux: High Mass Galaxies only

Regions around high mass galaxies are less transparent than those around normal galaxies because of the higher mean densityR

ED

CU

RV

E

The local photoionization produced by high mass galaxies can significantly clear the HI, only if such galaxies have very high star formation rates

(SFR > 100 M yr –1); still in this case is not able to explain the observations

GR

EEN

CU

RV

ES

UVB only

UVB + Galaxies, boosted SFR

UVB + Galaxies, SFR from MSPH

Adelberger etal , 2003

Japan - Italy Joint Seminar, 2003

Mean Ly Transmitted Flux: Low Mass Galaxies only

<F> mean Flux Ly trasmissivity r los/galaxy separation for

9 galaxies with M < 9 x 108 M

Regions around low mass galaxies are more transparent than thosearound normal galaxies due to thelower mean densityR

ED

CU

RV

E

The local photoionization could be significant if such galaxies have SFR higher than

50 M yr -1G

REEN

CU

RV

E

UVB only

UVB + Galaxies, SFR from MSPH

UVB + Galaxies, boosted SFR

Adelberger etal, 2003

2. Local Photoionization can partially explain the data if

CONCLUSIONS1. HI transparency close to LBGs cannot be explained by simulated winds (3 different independent results)

3. Data could be biased (poor statistics; opposite trend observed at lower redshift)

LBGs are massive galaxies

(very high SFR, 100-300 M/yr)

LBGs are low mass galaxies

(lower SFR > 50 M /yr)

DWARF STAR FORMING GALAXIES

Sommerville et al 1998, Dejaques et al 2003

Problem with SPH shock treatment ?