1. The Metagalactic Ultraviolet Background Jennifer E. Scott

2. Weymann et al. 1998 Kim et al. 2001 Dobrzycki et al. 2002 Redshift evolution of Ly  absorbers flattens with redshift

3. Dave et al. 1999 Evolution primarily driven by evolution in UVB

4. The Proximity Effect classical method The Ly  forest line density is modified by the presence of the quasar: Weyman, Carswell, & Smith 1981 Murdoch et al. 1986 Carswell et al. 1987 Bajtlik, Duncan, & Ostriker 1988 Lu et al. 1991

5. Redshift evolution- corrected line distribution Ratio of quasar flux to background flux Proximity effect line deficit JS et al. 2002

6. Log(mean intensity) also Lu et al. 1991 Cristiani et al. 1995 Giallongo et al. 1996 Srianand & Khare 1996 Line counting methods

7. Ly  Forest as FGPA  Match mean flux decrement in hydrodynamical simulations to observations of Ly  forest  Use shape of flux decrement distribution to test cosmological models Assume photoionization equilibrium negligible v pec thermal broadening Use effective e.o.s. Rauch et al. 1997

8. Bolton et al. 2005 Also McDonald & Miralda-Escude (2001) Meiksin & White (2004) Songaila et al. (2004) Tytler et al. (2004) Bolton et al. (2005) Kirkman et al. (2005) D’Odorico et al. (2008) Faucher-Giguere et al. (2008d)

9. Dall’Aglio et al. 2008a,b Wisotzki With high resolution & S/N data detect PE in individual quasar spectra and examine the distribution of PE strengths Bias (upwards) from using global approach to PE use modal value or “hybrid” method using a subsample with low overdensities and a correction for sample averaging using Monte-Carlo simulations Proximity effect revisited Instead of counting lines use flux transmission statistics change in  eff near quasars  eff = B(1+z)  +1 (1+  ) 1-  Lisk & Williger 2001 Proximity effect revisited Instead of counting lines use flux transmission statistics change in  eff near quasars  eff = B(1+z)  +1 (1+  ) 1-  Lisk & Williger 2001

10. Quasar systemic redshifts Many emission lines show shifts of several x 100 km/s with respect to systemic VandenBerk et al. 2001 Also Tytler & Fan 1992 McIntosh et al. 1999 Richards et al. 2002

11. Quasar Lyman limit fluxes HST composite spectrum Telfer et al. 2002

12. Quasars in overdense regions (Loeb & Eisenstein 1995, Rollinde et al. 2005, Guimaraes et al. 2007, Hennawi & Prochaska 2007, Prochaska & Hennawi 2009)  Overdensities to ~4 Mpc (D’Odorico et al. 2008, Faucher-Giguere et al. 2008a)  Overdensities and infall each contribute ~equally to overestimates of UVB from PE factor of ~(3.5,2.5,2) at z=(2,3,4) (Faucher-Giguere et al. 2008a)  Overdensities of factor of a few within 2.5 h -1 Mpc for chosen metagalactic UVB but no systematic enhancement- therefore can break degeneracy using overdensity distribution (high overdensity leads to tail in PESD) (Dall’Aglio et al. 2008b)

13. Hopkins et al. 2007 UVB Sources Quasar space density

14. Hopkins et al. 2007 Also Madau, Haardt, & Rees 1999 Bianchi, Cristiani, & Kim 2001 Quasars account for all of the observationally estimated  at z<1, and ~50% at z~2-3 But the quasar luminosity density drops off much faster than  at higher z z < 2: the faint quasar contribution is important z > 2: bright quasars dominate the luminosity density Bolton et al. (2005) (diamonds, z = 2-4) Tytler et al. (2004) (star, z = 1.9) Rollinde et al. (2005) (triangle, z = 2.75) McDonald & Miralda-Escude (2001, 2003) (squares, z = 2.4-5.2) Fan et al. (2006a) (circles, z = 5-6) JS et al. (2000) (boxes, z ~ 0-1 and z ~ 2-4) UVB Sources

15. Cosmological simulations with radiative transfer require stellar contribution to rise at z>3 to compensate for drop in quasar space density Sokasian, Abel, & Hernquist 2003 Proximity effect measurements UVB Sources

16. Faucher-Giguere et al. 2008d Faucher-Giguere et al. 2008b Sawicki & Thompson (2006) (Keck Deep Fields) Reddy et al. (2008) (Keck LBG) Yoshida et al. (2006) (Subaru Deep Field) Bouwens et al. (2007) (HUDF & other deep HST fields). Steidel et al. (1999) z~4 LBGs w/LF values of Reddy et al. (2008) UVB demands star formation at z>3 faint end slope? (cf. Rauch et al. 2008 faint LAEs 2.67<z<3.75) (Hopkins & Beacom) (Hernquist & Springel) UVB Sources

17. Inoue, Iwata, & Deharveng 2006 see also Sbrinovsky & Wyithe 2009 JS et al. 2000 Bolton et al. 2005 Fan et al. 2006b --- QSOs (Bianchi, Cristiani, & Kim 2001) ……galaxies UVB requires f esc =0.01 at z<1 =0.1 at z>4 UVB Sources

18. Steidel, Pettini, & Adelberger 2001 Composite spectrum- 29 LBGs Residual Lyman continuum flux Direct detection of LyC photons in only 2 of 14 LBGs Shapley et al. 2006

19. f esc * ~0.01 <0.02 ~0.05-0.25** *E(B-V)=0.15 and Calzetti et al. (2000) reddening law **Iwata et al. (2009) find similar value for 7 LBGs in a protocluster at z~3 with (f 1500 /f 900 ) stel ~1, for (f 1500 /f 900 ) stel =6, this becomes f esc ~0.4 Yajima: 0.17 < f esc < 0.47 for high z LBGs/LAEs Siana et al. 2007 (+2009)

20.  Low z and high z SFG spectra are similar (Schwartz et al. 2006)  Smaller f esc for low z galaxies explained if observed in pre-blowout phase in which LyC photons are inhibited (Fujita et al. 2003)  Also larger outflow velocities in galaxies with higher SFR/M (Grimes et al. 2009) and SFR/M increases with redshift (Damen et al. 2009)  Need f esc (t/z,L/M) to account for outflows, galaxy masses (Gnedin et al. 2008) and AGN duty cycles (McCandliss 2009) Complicating factors include: intrinsic Ly break ISM/IGM reddening values, extinction laws Complicating factors include: intrinsic Ly break ISM/IGM reddening values, extinction laws

21. UVB Spectrum probed by IGM metals (Ryan-Weber, Schaye, Becker, Fox, Bagla) He II Ly  forest (Fechner, Worseck) IGM photoheating from reionization  HI (Bolton) b distribution (Bolton)

22. Spectrum of UVB: He II Ly  forest Measure He II Ly  at z> 2 (FUSE) or z >2.8 (HST) to constrain ratio of UVB intensity or shape at 1 and 4 Ryd for photoionization equilibrium <200 for AGN-dominated UVB

23. He II quasars Q0302-003 z=3.3Jakobsen et al. 1994, Heap et al. 2000 Q1157+3143 z=3.0Reimers et al. 2005 HS1700+6416 z=2.7Davidsen et al. 1996, Fechner et al. 2006a,b PKS1935-692 z=3.1Tytler et al. 1995 SDSSJ2346-0016 z=3.5Zheng et al. 2004 HE2347-4342 z=2.8Reimers et al. 1997, Kriss et al. 2001 More to come… Syphers et al. 2008 Zheng et al. 2008 Worseck

24. Large observed fluctuations in  imply fluctuations in  HeII since  HI ~uniform at these redshifts Zheng et al. 2004 1 10 1000 100 HE 2374-4342

25. Fluctuations expected at He II reionization epoch from:  discrete sources and small He II ionizing photon mpf (esp. relative to HI) (Fardal et al. 1998, Bolton et al. 2006, McQuinn et al. 2008, Furlanetto & Oh 2008a, Furlanetto 2009a,b)  large dispersion of  s (Telfer et al. 2002, JS et al. 2004)  radiative transfer effects (Abel & Haehnelt 1999, Sokasian et al. 2002, Masseli & Ferrara 2005, Tittley & Meiksin 2007, McQuinn et al. 2008)  local sources (Jakobsen et al. 2003, Worseck & Wisotzki 2006, Worseck et al. 2007)

26. Agafonova et al. 2005, 2007 Reimers et al. 2006 Also Zheng et al. 2004 He II reionization Opacity increase at z~3 Consistent with increase in IGM temperature from photoionization Ricotti et al. 2000 Schaye et al. 2000 Theuns et al. 2002 But see Bolton, Oh, & Furlanetto 2009a

27. Change at z~3 Epoch of He II reionization Spectrum of UVB: Metals Songaila 1998, 2005  3-4 Ryd UVB needed for ionization corrections to measure IGM metallicity  Si IV & C IV IP straddle He II  Hardening at z≤3 Vladilo et al. 2003 Agafonova et al. 2005, 2007

28. But others find no break Also Aguirre et al. 2004 find observed IGM Si, C absorption cannot be reproduced using a spectrum with a transition due to He II ionization at z=3.2 Kim, Cristiani, & D’Odorico 2002 also Boksenberg et al. 2003 Spectrum of UVB: Metals

29. Spectrum of UVB: Metals Agafonova et al. 2007 No contribution from SFG needed to reproduce metal absorption -> f esc <0.05 HE2347-4342HS1700+6416 Sawtooth modulation from He II Ly series can depress UVB at 3-4 Ryd Madau & Haardt 2009

30. HI optical depth small filled circles 796 SDSS QSOs S/N >4 stars Sargent et al. (1989), diamonds Schneider et al. (1991) squares Zuo & Lu (1993) triangles McDonald et al. (2000) large filled circles Schaye et al. (2000) Bernardi et al. 2003 Also Faucher-Giguere et al. 2008c Dall’Aglio et al. 2008 But not seen by McDonald et al. 2005 Dip at z~3.2: change in T IGM ? change in n e ? enhancement in  HI ? (Bolton, Oh, & Furlanetto 2009b, Faucher-Giguere et al. 2008d)

31. Schaye et al. 2000 Also Ricotti et al. 2000, Theuns et al. 2002 Not seen by McDonald et al. 2001, Zaldarriaga et al. 2001 Doppler parameter distribution

32. Complications He II reionization process can lead to complex, multi-valued, even inverted EOS (Gleser et al. 2005, Becker et al. 2007, Furlanetto & Oh 2008b, Bolton et al. 2008) But see McQuinn et al. 2008 If hard photons deposit energy into high N HI systems, this will not be reflected in b boost to low N HI absorbers observed thus far uncertainty in interpreting temperature boost in IGM (Bolton, Oh, Furlanetto 2009a)

33. UVB models  Haardt & Madau 1996 QSOs + recombination emission  Haardt & Madau 2001 HM96 + galaxies  Bolton et al. 2005 scaling relations with cosmological parameters (e.g.  b,  8 ) and IGM properties (e.g.  eff, T)  Madau & Haardt 2009 He II forest  Faucher-Giguere et al. 2009 Updated galaxy, AGN LF Explicit consideration of He II reionization Lesser contribution from recombination emission, as informed by photoionization calculations

34. Faucher-Giguere et al. 2009 Ionizing spectra similar in shape after He II reionization Quasar contribution drops more rapidly than HM at z >2 but  HI boosted by enhanced galaxy contribution

35. Future Work  Luminosity functions at high z: faint source contributions  Galaxy f esc  AGN duty cycles  Quasar environments  Quasar systemic redshifts  Direct fluorescence measurements  COS: He II Ly  forest- fluctuations in  / local sources IGM Legacy- low z UVB  Models: Radiative transport Luminosity-dependent parameters, e.g. AGN spectral slope, f esc