Proximity Effect

Around High-redshift

Galaxies

Antonella Maselli, OAArcetri, Firenze, Italy

Collaborators: A.Ferrara, M. Bruscoli, S. Marri & R. Schneider

Crete, August 2004

z2 > z1

z1

no PE

PE

QSO Proximity Effect

Decrease in the number density of Ly absorption lines in the vicinity

of the background QSO

1981 Weymann et al first discussed the effect

suggesting its origin: the increased photoionization of the forest absorbers produced by the UV flux of the nearby QSO (Inverse Effect)

1982 Carswell et al confirmed the local origin of the

Inverse Effect

1988 Bajtlik et al confirmed the Carswell UVB intensity

measurement and coined the term Proximity Effect

1987 Carswell et al suggested the possibility to measure

the intensity of the UVB by properly modeling the PE, and performed the first crude measurement

To the observer

z1

PE

Crete, August 2004

Galaxy Proximity Effect

• Infall• Winds • Photo-ionization/Photo-heating

Effect produced by a Galaxy on the Ly

forest of a background QSO

The Ly forest at zglx can be affectedby several galaxy feedbacks

To the observer

zglx

Transverse PE

zQ > zglx

Crete, August 2004

1. Identify the spectroscopic

redshift of the galaxy, zglx

… in the field of a background

QSO, zQ > zglx

2. Study the statistical properties of the absorption

lines at zglx

Measure the physical state of the gas surrounding the galaxy as a function of the distance from it (impact parameter source/LOS )

Studying the Galactic PE

Crete, August 2004

z < 1

Lanzetta etal, 1995Chen etal, 1998Pascarelle etal, 2001

z 2.724 (LBG MS1521-cB58)

Savaglio etal, 2002

Absorption excess close to the galaxiesreflecting the high-density of glx sites }

z 3

Adelberger etal, 2002

• 8 bright QSOs at 3.1< z < 4.1

• 431 Lyman Break Galaxies at z3

Larger transmissivity in the inner comoving Mpc of LBGs

i.e., OPPOSITE TREND

Observed Proximity Effect of LBGs

Observed Proximity Effect of LBGs

• LBGs are associated with HI

overdensities on scales 1 Mpc < r < 7 Mpc

• LBGs are associated with HI

underdensities on scales < 1Mpc

Adelberger etal 2003z = 3

Observed Proximity Effect of LBGs

Adelberger etal 2003z = 3Interpretations for the

transparency of the inner region

• Observations are biased

• SNe Driven-Winds

• Local Photoionization

Adelberger et al, 2003

MSPH numerical data

Bruscoli et al 2003

z = 3

Numerical Simulations: WINDS

WINDS

UVB (Haardt & Madau 1996)

z = 3.26

LBOX = 10.5 Mpc h-1 comoving

Multiphase SPH simulation(Marri & White, 2002)

consistent withCroft et al (2002)

Kollmeier et al (2003)

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

OUTFLOWS CANNOTCLEAR THE GAS AROUND GALAXIES

AS REQUIRED BY OBSERVATIONS

Crete, August 2004

+Ionizing sources

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

Radiative Transfer Simulations: CRASH

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

Maselli etal 2004

Crete, August 2004

Sphere of influence of a typical galaxy

Local photoionization can be significant in determining the IGM ionization where:

Fgal/F bkg > 1

V(Fgal/F bkg > 1) 0.5% Vbox

Rinfluence 0.05 Mpc h-1 for a typical galaxy

in the simulation

Crete, August 2004

LBGs: observed properties & theoretical scenario

High luminousity

Strongly clustered

Massive isolated galaxies hosted in

very massive halos ( M > 1012 M ) Progenitors of the present universe ellipticals and spheroidals

[Steidel etal 1996, Giavalisco etal 1996 ]}Dwarf starbursting galaxies hosted in small mass halos, where an intense burst of star formation is triggered by merging [Lowental etal 1997, Somerville etal 2001 ]

Crete, August 2004

Neutral Hydrogen Fraction around LBGs candidates

SFR 90 M yr -1

SFR 29 M yr -1

SFR 0.09 M yr -1

SFR 290 M yr -1

9.2 × 108 M

8.7 × 1010 M

highest mass galaxy

lowest mass galaxy

NO galaxy

NO galaxy

4 M

pc h

-14

Mpc

h-1

Crete, August 2004

Neutral Hydrogen Fraction around LBGs candidates

9.2 × 108 M

8.7 × 1010 M

highest mass galaxy

lowest mass galaxy

0.8 Mpc h-1 comoving

No galaxySFR from SPHSFR boosted

Crete, August 2004

Mean Ly Transmitted Flux: High Mass vs Low Mass Galaxies

UVB only

UVB + Galaxies, boosted SFR

UVB + Galaxies, SFR from MSPH

Adelberger etal , 2003

UVB only

UVB + Galaxies, SFR from MSPH

UVB + Galaxies, boosted SFR

Adelberger etal, 2003

High Mass9 galaxies with M > 2 x 1010 M yr –1

Low Mass 9 galaxies with M 9 x 108 M yr –1

Conclusions

• Local photoionization has negligible effects for typical galaxies; it might be important for luminous (i.e. LBG) starburst galaxies

• SNe driven winds are ruled out as the origin of the observed transparency of the LBGs environment

Results

We have studied the possible origins of the LBG proximity effectobserved by Adelberger etal, via numerical simulations

LBGs are massive galaxies SFR 100-300 M/yr are required to reverse the trend of <F> close to LBGs.Insufficient to match the data

LBGs are dwarf SB galaxies

The data can be reproduced if

SFR > 50 M/yr

ENVIRONMENT IS THE KEY