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Redshift Evolution of Lya Absorbers in the Metagalactic Ultraviolet Background

This study explores the redshift evolution of Lya absorbers in the metagalactic ultraviolet background, focusing on the impact of quasar proximity effects and the role of UVB sources. The research utilizes observations, simulations, and statistical analysis to investigate the properties and distribution of Lya absorbers at different redshifts.

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Redshift Evolution of Lya Absorbers in the Metagalactic Ultraviolet Background

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  1. The Metagalactic Ultraviolet Background Jennifer E. Scott

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

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

  4. The Proximity Effect classical method The Lya 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 Proximity effect line deficit Ratio of quasar flux to background flux JS et al. 2002

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

  7. LyaForest as FGPA • Assume • photoionization equilibrium • negligible vpec • thermal broadening • Use effective e.o.s. • Match mean flux decrement in hydrodynamical simulations to observations of Lya forest • Use shape of flux decrement distribution to test cosmological models Rauch et al. 1997

  8. 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) Bolton et al. 2005

  9. Proximity effect revisited Instead of counting lines use flux transmission statistics change in teff near quasars teff = B(1+z)g+1(1+w)1-b Lisk & Williger 2001 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 Dall’Aglio et al. 2008a,b Wisotzki

  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. UVB Sources Quasar space density Hopkins et al. 2007

  14. UVB Sources Quasars account for all of the observationally estimated G at z<1, and ~50% at z~2-3 But the quasar luminosity density drops off much faster than G 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) Hopkins et al. 2007 Also Madau, Haardt, & Rees 1999 Bianchi, Cristiani, & Kim 2001

  15. Proximity effect measurements UVB Sources 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

  16. UVB Sources • UVB demands star formation at z>3 • faint end slope? • (cf. Rauch et al. 2008 faint LAEs 2.67<z<3.75) 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) (Hernquist & Springel) (Hopkins & Beacom) Faucher-Giguere et al. 2008d

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

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

  19. Siana et al. 2007 fesc* ~0.01 <0.02 ~0.05-0.25** (+2009) *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 (f1500/f900)stel~1, for (f1500/f900)stel=6, this becomes fesc~0.4 Yajima: 0.17 < fesc < 0.47 for high z LBGs/LAEs

  20. Complicating factors include: • intrinsic Ly break • ISM/IGM reddening values, extinction laws • Low z and high z SFG spectra are similar (Schwartz et al. 2006) • Smaller fesc 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 fesc(t/z,L/M) • to account for outflows, galaxy masses (Gnedin et al. 2008) • and AGN duty cycles (McCandliss 2009)

  21. UVB Spectrum probed by • IGM metals (Ryan-Weber, Schaye, Becker, Fox, Bagla) • He II • Lya forest (Fechner, Worseck) • IGM photoheating from reionization • tHI (Bolton) • b distribution (Bolton)

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

  23. He II quasars More to come… Syphers et al. 2008 Zheng et al. 2008 Worseck

  24. HE 2374-4342 Large observed fluctuations in h imply fluctuations in GHeII since GHI ~uniform at these redshifts 1000 100 10 1 Zheng et al. 2004

  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 as(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. He II reionization 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 Opacity increase at z~3 Agafonova et al. 2005, 2007 Reimers et al. 2006 Also Zheng et al. 2004

  27. Spectrum of UVB: Metals • 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 Change at z~3 Epoch of He II reionization Songaila 1998, 2005

  28. Spectrum of UVB: Metals 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

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

  30. HI optical depth • Dip at z~3.2: • change in TIGM? • change in ne? • enhancement in GHI ? • (Bolton, Oh, & Furlanetto 2009b, • Faucher-Giguere et al. 2008d) 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

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

  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 NHI systems, this will not be reflected in b boost to low NHI 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. Wb, s8) and IGM properties (e.g. teff, 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. Ionizing spectra similar in shape after He II reionization Quasar contribution drops more rapidly than HM at z >2 but GHI boosted by enhanced galaxy contribution Faucher-Giguere et al. 2009

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

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