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Proximity Effect Around High-redshift Galaxies

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15 diapositives · 296 Views · Aug 22, 2014

This study delves into the Proximity Effect (PE) surrounding high-redshift galaxies (Lyman Break Galaxies, LBGs) and their influence on the Lyman alpha forest of background quasar light. Originally discussed by Weymann et al., the PE signifies a decrease in the density of Lyman-alpha absorption lines around luminous quasars due to enhanced photoionization. Following investigations have confirmed its origin, leading to methods for measuring the intensity of the UV background (UVB) using statistical properties of absorption lines. This research underscores the complexities in understanding galaxy feedback mechanisms and their implications on cosmic structure formation.

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Proximity Effect Around High-redshift Galaxies
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  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