Proximity Effect Around High-redshift Galaxies

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

2. z2 > z1 PE z1 z1 no PE PE To the observer 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 forestabsorbers produced by the UV flux • of the nearby QSO (Inverse Effect) • 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. zQ > zglx zglx TransversePE To the observer Galaxy Proximity Effect 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. z < 1 Lanzetta etal, 1995 Chen etal, 1998 Pascarelle etal, 2001 z  2.724 (LBG MS1521-cB58) Savaglio etal, 2002 Observed Proximity Effect of LBGs } Absorption excess close to the galaxies reflecting the high-density of glx sites 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 Adelbergeretal 2003 z = 3 • LBGs are associated with HI • overdensities on scales • 1 Mpc < r <7 Mpc • LBGs are associated with HI • underdensities on scales < 1Mpc

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

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

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

10. Rinfluence  0.05Mpc h-1 for a typicalgalaxy in the simulation 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 Crete, August 2004

11. 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 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

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

13.  0.8 Mpc h-1 comoving Neutral Hydrogen Fraction around LBGs candidates 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. 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 Mean Ly Transmitted Flux: High Mass vs Low Mass Galaxies High Mass 9 galaxies with M > 2 x 1010 M yr –1 Low Mass 9 galaxies with M  9 x 108 M  yr –1 Crete, August 2004

15. SFR 100-300 M/yr are required to reverse the trend of <F> close to LBGs. Insufficient to match the data LBGs are massive galaxies The data can be reproduced if SFR > 50 M/yr LBGs are dwarf SB galaxies 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 photoionizationhas negligible effects for typical galaxies; • it might be important for luminous (i.e. LBG) starburst galaxies ENVIRONMENT IS THE KEY