Proximity Effect
Around High-redshift
Galaxies
Antonella Maselli, OAArcetri, Firenze, Italy
Collaborators: A.Ferrara, M. Bruscoli, S. Marri & R. Schneider
z 2 > z1
QSO Proximity Effect
PE
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
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
1988
Bajtlik et al confirmed the Carswell UVB intensity
z1
z1
no PE
PE
measurement and coined the term Proximity Effect
Crete, August 2004
To the observer
Galaxy Proximity Effect
zQ > zglx
Effect produced by a Galaxy on the
Ly
forest of a background QSO
The Ly forest at zglx can be affected
zgl
x
by several galaxy feedbacks
•
•
•
Infall
Winds
Photo-ionization/Photo-heating
Transverse PE
To the observer
Crete, August 2004
Studying the Galactic PE
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 )
Crete, August 2004
Observed Proximity Effect of LBGs
z<1
Lanzetta etal, 1995
Chen etal, 1998
Pascarelle etal, 2001
z  2.724 (LBG MS1521-cB58)
Savaglio etal, 2002
}
Absorption excess close to the galaxies
reflecting the high-density of glx sites
z3
Adelberger etal, 2002
• 8
bright QSOs at 3.1< z < 4.1
Larger transmissivity in the inner
comoving Mpc of LBGs
• 431 Lyman Break Galaxies at z3
i.e., OPPOSITE TREND
Crete, August 2004
Observed Proximity Effect of LBGs
z=3
Adelberger etal 2003
• LBGs are associated with HI
overdensities on scales
1 Mpc < r < 7 Mpc
• LBGs are associated with HI
underdensities on scales < 1Mpc
Observed Proximity Effect of LBGs
z=3
Adelberger etal 2003
Interpretations for the
transparency of the inner
region
• Observations are biased
• SNe Driven-Winds
• Local Photoionization
Numerical Simulations: WINDS
Multiphase SPH simulation
(Marri & White, 2002)
z=3
Bruscoli et al 2003
Adelberger et al, 2003
MSPH numerical data
WINDS
UVB (Haardt & Madau 1996)
z = 3.26
LBOX = 10.5 Mpc h-1 comoving
398 galaxies identified with a
HOP group finding algorithm
(Eisenstein & Hut, 1998)
OUTFLOWS CANNOT
CLEAR THE GAS AROUND GALAXIES
AS REQUIRED BY OBSERVATIONS
consistent with
Croft et al (2002)
Kollmeier et al (2003)
Radiative Transfer Simulations: CRASH
Arbitrary 3-D
precomputed
Multiphase
SPH
simulation
cosmological
H/He density
3-D
gas distribution
(nH, T,field
xI)
OUTPUTS
+
Ionizing sources
Maselli etal 2004
• Multiple
398 galaxies
point(Lsources
 SFR , Starbust99 )
• Background
UVB, (Haardt(UVB)
& Madau 1996)
• Diffuse radiation
from recombinations
Crete, August 2004
Time evolution of
TEMPERATURE
and
IONIZATION FRACTIONS
inside the simulation
volume
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
Massive isolated galaxies hosted in
very massive halos ( M > 1012 M )
Progenitors of the present universe ellipticals
and spheroidals
High luminousity
}
[Steidel etal 1996, Giavalisco etal 1996 ]
Strongly clustered
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
NO galaxy
SFR  29 M  yr -1
SFR  290 M  yr -
SFR  0.09 M  yr -1
SFR  90 M  yr -1
1
highest mass galaxy
8.7 × 1010 M
NO galaxy
lowest mass galaxy
9.2 × 108 M
Crete, August 2004
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
Mean Ly Transmitted Flux: High Mass vs Low Mass Galaxies
High Mass
9 galaxies with M > 2 x
Low Mass
1010
M yr
–1
9 galaxies with M  9 x 108 M  yr –1
Adelberger etal , 2003
Adelberger etal, 2003
UVB only
UVB only
UVB + Galaxies, SFR from MSPH
UVB + Galaxies, SFR from MSPH
UVB + Galaxies, boosted SFR
UVB + Galaxies, boosted SFR
Crete, August 2004
Conclusions
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
LBGs are dwarf SB galaxies
SFR 100-300 M/yr are required to
reverse the trend of <F> close to LBGs.
Insufficient to match the data
The data can be reproduced if
SFR > 50 M/yr