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

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

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

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

} 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  2.724 (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

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

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

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)

+ 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

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 Massive isolated galaxies hosted in very massive halos ( M > 1012 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 2001 ] Crete, August 2004

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

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 9 galaxies with M > 2 x 1010 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 , 2003 UVB only UVB + Galaxies, SFR from MSPH UVB + Galaxies, boosted SFR Adelberger etal, 2003 Crete, August 2004

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 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