1. Proximity Effect Around High-redshift Galaxies
Antonella Maselli, OAArcetri, Firenze, Italy
Collaborators: A.Ferrara, M. Bruscoli, S. Marri & R. Schneider

2. Decrease in the number density of Ly absorption lines in the vicinity
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
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)
To the observer z1 PE
Carswell et al confirmed the local origin of the
Inverse Effect
Carswell et al suggested the possibility to measure
the intensity of the UVB by properly modeling the PE,
and performed the first crude measurement
Bajtlik et al confirmed the Carswell UVB intensity
measurement and coined the term Proximity Effect
Crete, August 2004

3. Galaxy Proximity Effect
To the observer
zglx
Transverse PE
zQ > zglx
Effect produced by a Galaxy on the Ly
forest of a background QSO
The Ly forest at zglx can be affected
by several galaxy feedbacks
Infall
Winds
Photo-ionization/Photo-heating
Crete, August 2004

4. Studying the Galactic PE
1. Identify the spectroscopic
redshift of the galaxy, zglx
… in the field of a background
QSO, zQ > zglx
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 )
Crete, August 2004

5. } Observed Proximity Effect of LBGs z < 1 Lanzetta etal, 1995
Chen etal, 1998
Pascarelle etal, 2001 }
Absorption excess close to the galaxies
reflecting the high-density of glx sites
z  (LBG MS1521-cB58)
Savaglio etal, 2002
z  3
Adelberger etal, 2002
Larger transmissivity in the inner
comoving Mpc of LBGs
8 bright QSOs at 3.1< z < 4.1
431 Lyman Break Galaxies at z3
i.e., OPPOSITE TREND
Crete, August 2004

6. Observed Proximity Effect of LBGs
Adelberger etal 2003
z = 3
LBGs are associated with HI
overdensities on scales
1 Mpc < r < 7 Mpc
underdensities on scales < 1Mpc

7. Interpretations for the transparency of the inner
Observed Proximity Effect of LBGs
Adelberger etal 2003
z = 3
Interpretations for the transparency of the inner
region
Observations are biased
SNe Driven-Winds
Local Photoionization

8. Numerical Simulations: WINDS
Adelberger et al, 2003
MSPH numerical data
Bruscoli et al 2003
z = 3
Multiphase SPH simulation
(Marri & White, 2002)
WINDS
UVB (Haardt & Madau 1996)
z = 3.26
LBOX = 10.5 Mpc h-1 comoving
OUTFLOWS CANNOT
CLEAR THE GAS AROUND GALAXIES
AS REQUIRED BY OBSERVATIONS
398 galaxies identified with a
HOP group finding algorithm
(Eisenstein & Hut, 1998)
consistent with
Croft et al (2002)
Kollmeier et al (2003)

9. + Radiative Transfer Simulations: CRASH Multiphase SPH simulation
Maselli etal 2004
Multiphase SPH simulation
3-D gas distribution (nH, T, xI)
Arbitrary 3-D precomputed
cosmological H/He density field
Time evolution of
TEMPERATURE
and
IONIZATION FRACTIONS
inside the simulation
volume
OUTPUTS +
Ionizing sources
Multiple point sources
398 galaxies (L  SFR , Starbust99 )
Background (UVB)
Diffuse radiation
from recombinations
UVB, (Haardt & Madau 1996)
Crete, August 2004

10. 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  Mpc h for a typical galaxy
in the simulation
Crete, August 2004

11. } LBGs: observed properties & theoretical scenario High luminousity
Massive isolated galaxies hosted in
very massive halos ( M > M )
Progenitors of the present universe ellipticals
and spheroidals }
High luminousity
Strongly clustered
[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 ]
Crete, August 2004

12. Neutral Hydrogen Fraction around LBGs candidates
NO galaxy
SFR  29 M  yr -1
SFR  290 M  yr -1
highest mass galaxy
8.7 × 1010 M
4 Mpc h-1
NO galaxy
SFR  0.09 M  yr -1
SFR  90 M  yr -1
lowest mass galaxy
9.2 × 108 M
4 Mpc h-1
Crete, August 2004

13. Neutral Hydrogen Fraction around LBGs candidates
 0.8 Mpc h-1 comoving
highest mass galaxy
8.7 × 1010 M
No galaxy
SFR from SPH
SFR boosted
lowest mass galaxy
9.2 × 108 M
Crete, August 2004

14. Mean Ly Transmitted Flux: High Mass vs Low Mass Galaxies
9 galaxies with M > 2 x M yr –1
Low Mass
9 galaxies with M  9 x 108 M  yr –1
UVB only
UVB + Galaxies, boosted SFR
UVB + Galaxies, SFR from MSPH
Adelberger etal ,
UVB only
UVB + Galaxies, SFR from MSPH
UVB + Galaxies, boosted SFR
Adelberger etal,
Crete, August 2004

15. Conclusions Results ENVIRONMENT IS THE KEY LBGs are massive galaxies
We have studied the possible origins of the LBG proximity effect
observed by Adelberger etal, via numerical simulations
Results
SNe driven winds are ruled out as the origin of the
observed transparency of the LBGs environment
Local photoionization has negligible effects for typical galaxies;
it might be important for luminous (i.e. LBG) starburst galaxies
ENVIRONMENT IS THE KEY
LBGs are massive galaxies
SFR 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