1. Radiative Transfer Simulations The Proximity Effect of LBGs: Antonella Maselli, OAArcetri, Firenze, Italy Collaborators: A.Ferrara, M. Bruscoli, S. Marri & R. Schneider Marri et al 2003, in preparation Bruscoli et al, 2003,MNRAS,343,L45 Maselli et al, 2003,submitted to MNRAS

2. Japan - Italy Joint Seminar, 2003 Theoretical Expectations The physical properties of IGM close to galaxies can be studied through the statistics of absorption lines associated with foreground galaxies in QSOs spectra Predictions: HIGHER NUMBER OF STRONG Ly  ABSORPTION LINES LOWER MEAN Ly  TRANSMITTED FLUX at smaller l.o.s./galaxy impact parameters

3. 8 bright QSOs at 3.1< z <4.1 431 Lyman Break Galaxies at z  3 OBSERVATIONS: Results Adelberger et al (2002) LBGs are associated with HI overdensities at scales 1 Mpc < r < 7 Mpc LBGs are associated with HI underdensities at scales < 1Mpc

4. 8 bright QSOs at 3.1< z <4.1 431 Lyman Break Galaxies at z  3 OBSERVATIONS: Results Adelberger et al (2002) Interpretations for the transparency of the inner region Observations are biased SNe Driven-Winds Local Photoionization

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

6. COMMON ASSUMPTION : PHOTONS ESCAPING FROM LBGs HAVE A MEAN FREE PATH EQUAL TO THAT IN THE IGM   240 Mpc h -1 LOCAL PHOTOIONIZATION ? cando the job ? Croft et al (2002) Kollmeier et al (2003) Adelberger et al (2003) Analytical approach Numerical approach } Negative answer THE IGM IN THE VICINITY OF GALAXIES HAS BIASED PHYSICAL PROPERTIES FULL CONSISTENT RADIATIVE TRANSFER SIMULATIONS ARE NEEDED TO ANSWER THE QUESTION

7. Japan - Italy Joint Seminar, 2003 Sphere of influence of a typical galaxy Local photoionization can be significant in determining the ionization state of the IGM where : F gal /F bkg > 1 V( F gal /F bkg > 1 )  5 % V box R influence  0.4 Mpc h -1 for a typical galaxy in the simulation

8. Japan - Italy Joint Seminar, 2003 + Ionizing sources Multiple point sources Background (UVB) Diffuse radiation from recombinations Radiative Transfer Simulations: CRASH Maselli et al (2003) Arbitrary 3-D precomputed cosmological H/He density field Multiphase SPH simulation 3-D gas distribution (n H, T, x I ) 398 galaxies (L  SFR, Starbust99 ) UVB, (Haardt & Madau 1996) Time evolution of TEMPERATURE and IONIZATION FRACTIONS inside the simulation volume OUTPUTS

9. Japan - Italy Joint Seminar, 2003 Neutral Hydrogen Fraction 90 M  yr -1 SFR  0.09 M  yr -1 290 M  yr -1 9.2 x 10 8 M  8.7 x 10 10 M  Less massive galaxy NO galaxy 4 Mpc h -1 NO galaxy SFR  29 M  yr -1 Most massive galaxy

10. Japan - Italy Joint Seminar, 2003 Neutral Hydrogen Fraction SFR  90 M  yr -1 SFR  29 M  yr -1 SFR  0.09 M  yr -1 SFR  290 M  yr -1 9.2 x 10 8 M  8.7 x 10 10 M  Most massive galaxy Less massive galaxy NO galaxy 4 Mpc h -1

11. Japan - Italy Joint Seminar, 2003 Neutral Hydrogen Fraction along LOS across galaxies SFR  290 M  yr -1 Log (x HI ) UVB SFR from SPH SFR boosted along xalong yalong z  1 Mpc h -1 comoving SFR  29 M  yr -1 8.7 x 10 10 M  SFR  0.09 M  yr -1 SFR  90 M  yr -1 lowest mass galaxy highest mass galaxy 9.2 x 10 8 M 

12. Japan - Italy Joint Seminar, 2003 Mean Ly  Transmitted Flux: UVB & Galaxies mean Flux Ly  trasmissivity  r los/galaxy separation for 398 galaxies The UV emission by galaxies has little effect on the mean Ly  trasmissivity of the IGM

13. Japan - Italy Joint Seminar, 2003 mean Flux Ly  trasmissivity  r los/galaxy separation for 9 galaxies with M > 2 x 10 10 M  Mean Ly  Transmitted Flux: High Mass Galaxies only Regions around high mass galaxies are less transparent than those around normal galaxies because of the higher mean density RED CURVE The local photoionization produced by high mass galaxies can significantly clear the HI, only if such galaxies have very high star formation rates (SFR > 100 M  yr –1 ); still in this case is not able to explain the observations GREEN CURVES UVB only UVB + Galaxies, boosted SFR UVB + Galaxies, SFR from MSPH Adelberger etal, 2003

14. Japan - Italy Joint Seminar, 2003 Mean Ly  Transmitted Flux: Low Mass Galaxies only mean Flux Ly trasmissivity  r los/galaxy separation for 9 galaxies with M < 9 x 10 8 M  Regions around low mass galaxies are more transparent than those around normal galaxies due to the lower mean density RED CURVE The local photoionization could be significant if such galaxies have SFR higher than 50 M  yr -1 GREEN CURVE UVB only UVB + Galaxies, SFR from MSPH UVB + Galaxies, boosted SFR Adelberger etal, 2003

15. 2. Local Photoionization can partially explain the data if CONCLUSIONS 1.HI transparency close to LBGs cannot be explained by simulated winds ( 3 different independent results) 3. Data could be biased ( poor statistics; opposite trend observed at lower redshift ) LBGs are massive galaxies (very high SFR, 100-300 M  /yr) LBGs are low mass galaxies (lower SFR > 50 M  /yr) DWARF STAR FORMING GALAXIES Sommerville et al 1998, Dejaques et al 2003 Problem with SPH shock treatment ?