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Early galaxies/AGNs and Reionization

Explore the key aspects of reionization, from hydrogen reionization to the end of the Dark Ages, highlighting galaxies and AGNs as cosmic tools to understand this critical phase transition in the Universe. Discover future prospects and constraints on reionization through various observational methods and measurements.

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Early galaxies/AGNs and Reionization

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  1. Early galaxies/AGNs and Reionization Andrea Grazian (INAF-OAR) June 27th, 2018 ASI-COSMOS Meeting (Ferrara)

  2. Outline Reionization: what and when ? Galaxies and AGNs as cosmic tools to constrain Reionization Galaxies and AGNs as main drivers of Reionization ? Future Prospects

  3. Reionization: What ? Hydrogen Reionization: major phase transition of the Universe Recombination Hydrogen reionization End of Dark Ages

  4. Epoch of Reionization: When ? Becker et al. (2015) Recombination Fan et al. (2006) Even a tiny neutral fraction xHI~10^-4 gives rise to complete GP absorption 1 Gunn-Peterson troughs suggest reionization ending at z=5.5-6.0 (Fan et al. 2006; Becker et al. 2015; Bosman et al. 2018)

  5. Epoch of Reionization: When ? + => 6 < z < 9 Thomson scattering optical depth measured in CMB Recombination Planck 2016 result: =0.055+/-0.009 z_reion=7.8+/-1.0 (2016 A&A 596, 107) Planck 2016 result: =0.058+/-0.012 z_reion=8.5+/-1.0 (2016 A&A 596, 108) • Implies reionization at z<~9. Rapid process CAVEAT: simple parameterization is assumed z_reion<9 z_reion>6 Fast and Late Reionization

  6. Constraining Reionization CMB optical depth Gunn-Peterson optical depth Patchy kinetic SZ effect (kSZ) Lyman Alpha Emitter Luminosity Function evolution at z>6 Lyman Alpha fraction in Lyman Break galaxies at z>6 Lyman Alpha Emitter Clustering Damping wing in high-z QSOs and GRBs Dark fraction of pixels in deep QSO spectra (Dark gap statistics) Size of near-zone of QSOs 21cm power spectrum (see talk by C. Burigana)

  7. Patchy kinetic SZ effect kSZ: secondary CMB anisotropy due to electrons with bulk flows. Inhomogeneous reionization → patchy kSZ. Depends on timing, duration, and topology of reionization George et al. 2015 Scales of l~3000 D~20 Mpc Typical scales at EoR

  8. Patchy kSZ effect George et al. 2015 Planck 2016 Combining Planck 2016 and SPT kSZ: z<2.8

  9. Lyman Alpha Line Lyman alpha line (1216 A) is a resonant transition: Lya photons scatter back and forth until they are absorbed by dust or redshifted. The visibility of Lyman alpha line is modulated by the IGM neutral fraction and by the velocity of gas. Lyman Alpha Emitters (LAEs) are Star-Forming Galaxies with strong Lyman Alpha in emission and faint continuum. Lyman Break Galaxies (LBGs) are Star Forming Galaxies with strong continuum (can be weak in Lya). Iye et al. 2011 Mason et al. 2018

  10. Lyman Alpha Emitters Luminosity Function LAE LF does not evolve at 3<z<5.7, but shows strong evolution at z>5.7: Damping of Lyman alpha photons by partially neutral IGM ? (Konno et al. 2014, 2017; Santos et al. 2016; Ota et al. 2017) UV properties of LAEs are crucial. Santos et al. 2016 RESULTS: x_HI(z)=0.3+/-0.2 at z=6.6 (Konno et al. 2017) x_HI(z)>0.4 at z=7 (Ota et al. 2017) x_HI(z)=0.25+/-0.25 at z=7 (Itoh et al. 2018) CAVEATS: Degeneracy between escape fraction of Lya photons vs IGM neutral fraction; Lya duty cycle; inflow/outflow;

  11. Lyman Alpha Fraction in Lyman Break Galaxies Mason et al. 2018 Mason et al. 2018 The equivalent width (EW) distribution of Lyman alpha lines in LBG galaxies is modulated by the IGM neutral fraction xHI. CAVEATS: Escape fraction of Lyman Continuum photons; intrinsic Lya profile; inflow/outflow; uncertainties on Lyman alpha fraction at z<6; dust content.

  12. Lyman Alpha Fraction in Lyman Break Galaxies Mason et al. 2018 RESULTS: x_HI(z)=0.59+0.11-0.15 at z=7.0 (Mason et al. 2018) x_HI(z)=0.39+/-0.09 at z~7 (Schenker et al. 2014) x_HI(z)>0.64 at z~8 (Schenker et al. 2014)

  13. Clustering of Lyman Alpha Emitters Ouchi et al. 2017 The strength of the Lyman alpha absorption from the IGM depends on the spatial distribution of galaxies and cosmic neutral hydrogen patches (Furlanetto et al. 2006; McQuinn et al. 2007). Strong clustering of LAEs can be due to large patches of neutral hydrogen (HI). RESULTS: x_HI(z)<0.30 at z=6.6 (Ouchi et al. 2017) CAVEAT: degeneracy with dark matter evolution

  14. Damping wing in high-z QSO spectra z=7.54 Banados et al. 2018 CAVEATS: degeneracy between the damping wing from cosmic HI and from a possible high column density DLAS associated. Uncertainties in the intrinsic emission profile of Lyman alpha.

  15. Damping wing in high-z QSO spectra Banados et al. 2018 RESULTS: x_HI(z)=0.56+0.21-0.18 at z=7.54 (Banados et al. 2018) x_HI(z)=0.40+0.21-0.19 at z=7.01 (Mortlock et al. 2011)

  16. Damping wing in high-z GRB spectra Totani et al. 2006 CAVEATS: uncertainties on the distance from host galaxy; local ISM vs IGM

  17. Damping wing in high-z GRB spectra Totani et al. 2014 Dark Gunn-Peterson trough Associated with neutral IGM Reionization is not complete at z~6 But different results from Subaru and VLT spectra of GRB130606A (Hartoog et al. 2015 find xHI<0.05 at 3 sigma) RESULTS: x_HI(z)<0.17 at z=6.36 (Totani et al. 2006) x_HI(z)=0.1-0.5 at z=5.91 (Totani et al. 2014) x_HI(z)=0.06 at z=5.91 (Totani et al. 2016) x_HI(z)=0.12+/-0.05 at z=6.33 (Chornock et al. 2014)

  18. Dark fraction of pixels in deep QSO spectra Fraction of Lya and Lyb dark pixels provides a model independent upper limit on xHI Reionization is almost complete at z~5.5-6.0 (McGreer et al. 2015; Becker et al. 2015; Bosman et al. 2018) McGreer et al. 2015

  19. Dark fraction of pixels in deep QSO spectra McGreer et al. 2015 RESULTS: x_HI(z)<0.09 at z=5.6 (McGreer et al. 2015) x_HI(z)<0.11 at z=5.9 (McGreer et al. 2015) x_HI(z)<0.60 at z=6.1 (McGreer et al. 2015)

  20. Size of near-zone of QSOs Size of proximity region around high-z QSOs Transmission blueward of Lya due to strong QSO radiation CAVEAT: degeneracies with QSO age, photo-ionization rate in the surrounding IGM, presence of associated DLAS Bolton et al. 2011 RESULTS: x_HI(z)>0.1 at z=7.1 (Mortlock et al. 2011; Bolton et al. 2011)

  21. Reionization before Planck Fan et al. 2006

  22. Reionization after Planck Ota et al. 2017 Consistent picture: late and fast Reionization, almost complete at z~8.0-8.5; Greig & Mesinger (2017): z_reion=7.57+0.78-0.73, Delta_z_reion=1.7 (see talk by M. Migliaccio) Tension with Planck 2016 ???

  23. Sources of Reionization Reionization: driven by Galaxies or AGNs or else ? At high-z bright QSOs are rare. Low ionizing emissivity by QSOs at z>3 (Cowie et al. 2009). Faint Galaxies can be Important at z>3. Steep Luminosity Functions. Large contribution by faint galaxies (Muv=-12) to the ionizing background if their fesc>15%. (see talk by N. Dal Pra) (Haardt & Madau 2012) QSOs SFGs

  24. Production of ionizing radiation Density of Ionizing photons UV Luminosity Density at 1500A rest frame LyC photons per unit UV Luminosity at 1500A Escape fraction of LyC photons Critical paramater for galaxies: uncertain

  25. The LyC Escape Fraction of Galaxies At z<3 the observed escape fraction of bright galaxies is <1-2% Very few detections of LyC Emitters At z=3-4 LyC escape fraction is <2-5%, Grazian et al. (2016, 2017) Consistent with Vasei et al. (2016), Guaita et al. (2016), Smith et al. (2016), Japelj et al. (2017), Marchi et al. (2017), Rutkowski et al. (2017) At z~6, Kakiichi et al. (2018) find fesc=8% at M1500<-14.5 Tanvir et al. (2018) find fesc<0.5% at 1.6<z<6.7 from GRBs deep spectra: no correlation of fesc with luminosity or stellar mass. WARNING: galaxies have low LyC escape fraction; Fesc>15-20% required for Reionization (Puchwein et al. 2018)

  26. Sources of Reionization Reionization: driven by Galaxies or AGNs ? Planck Collaboration (2016) z_reion=7.8+/-1.0: late reionization SPT kSZ effect (Zahn et al. 2012): Delta_z_reion<2.8: rapid process Greig & Mesinger (2017): rapid evolution of HI fraction at z~7 Rapid evolution of Ly-alpha fraction at z>7: late reionization z_reion~7; patchy topology of reionization (Schmidt et al. 2016; Mason et al. 2018) Large Lyman-alpha opacity fluctuations in z>6 QSO absorption spectra: bright and rare ionizing sources (Chardin et al. 2016, 2017) Long trough in z>6 QSO absorption spectra: difficult with numerous low-luminosity sources (Becker et al. 2015) Prevalence of AGNs in LyC candidates at z~2 (Naidu et al. 2016) Low LyC fesc from galaxies with high OIII/OII line ratio (Naidu et al. 2018) Probably driven by rare and bright sources with large LyC fesc

  27. The LyC Escape Fraction of QSOs/AGNs M1450=-26 QSOs (L~5L*) have fesc~75% (or more). What about fainter AGNs ? Cristiani et al. (2016) No dependence of LyC fesc from Luminosity has been detected Grazian et al. (2018)

  28. The contribution of faint AGN to the Photoionization rate AGNs at z~4 can produce >65-85% of the UVB, assuming the G15 Luminosity Function and fesc=75% down to M1450=-18 (0.01L*). In the future it will be crucial to study the LF near L* and measure fesc for AGN fainter than M1450=-22. Giallongo et al. (2015)

  29. Future Prospects LSST, Euclid, WFIRST Find QSOs at z>8 (Gunn-Peterson effect, dark gap statistics, damping wing, sizes of near-zone, luminosity function) JWST, ELTs Luminosity function and clustering of LAEs, Lyman alpha fraction of LBGs SKA 21cm tomography: topology of Reionization; cross-correlation 21cm-Lyman alpha lines Athena, Theseus X-ray surveys (high-z AGNs); high-z GRBs FRBs ?

  30. Thank you!

  31. Greig & Mesinger 2017

  32. Ouchi et al. (2018) Konno et al. (2017) Ouchi et al. (2018) Konno et al. (2017)

  33. The contribution of faint AGN to the Photoionization rate AGNs at z~4 can produce >65-85% of the UVB, assuming the G15 Luminosity Function and fesc=75% down to M1450=-18 (0.01L*). In the future it will be crucial to study the LF near L* and measure fesc for AGN fainter than M1450=-22.

  34. Photo-ionization rate A decline by a factor ~10 from z~4 to z~6 due to decrease of both emissivity and mean free path Still consistent with the degree of ionization of IGM Giallongo et al. (2015)

  35. Galaxies vs AGNs ? Rapid Reionization at z~7-8 difficult to explain only with galaxies; Chardin et al. (2016): large UVB fluctuations can be indication of AGN dominated reionization Becker et al. 2015 Long and dark trough at z~6

  36. CMB optical depth CAVEAT: simple parameterization is assumed

  37. UV Luminosity Density of galaxies Main contribution by low luminosity galaxies Bouwens et al. 2015

  38. Galaxy LyC photon production rate Bouwens et al. 2015 Rate depends on dust content, Metallicity, stellar rotation (e.g. BPASS, Elridge & Stanway 2015)

  39. LyC Escape Fraction of z~3 Galaxies 23% 23% 23% 10% 2.0% 2.4% 2.5% 69 galaxies 1.7% See also Siana et al. 2015 Grazian et al. (2017)

  40. Contamination by foreground VUDS-LBC/COSMOS Global fesc=230% Grazian et al. (2016) Local fesc=520% See also Vanzella et al. (2010) and Siana et al. (2015) Contamination by Foreground galaxy

  41. Production of ionizing radiation Ionizing Emissivity Density of Ionizing photons UV Luminosity Density at 1500A rest frame LyC photons per unit UV Luminosity at 1500A Escape fraction of LyC photons

  42. HI Photoionization rate UVB by bright galaxies (L>0.5L*) Grazian et al. (2016) Gamma<0.29

  43. Low-z LyC Emitters Local galaxies with OIII/OII>5 and compact morphology. Muv~-20 High ionizing photon production efficiency (Schaerer et al. 2016) See also Leitet et al. 2013; Borthakur et al. 2014; Leitherer et al. 2016; Bergvall et al. 2016; (Izotov et al. 2016a)

  44. LyC Emitter at z=3.2 Similar properties of galaxies by Izotov et al. 2016a,b OIII/OII>10 and compact morphology in LyC. Muv~-21 See also Steidel et al. 2001; Shapley et al. 2006; Nestor et al. 2013; Shapley et al. 2016; Reddy et al 2016; Bian 2017 (Vanzella et al. 2016) Important to understand their physical properties at z<4: Find LyC emitter analogs at z>6 With indirect technique. Study the LyC emission of whole population of SFGs

  45. Results on Star Forming Galaxies Bian et al. (2017) 1 out of 7 galaxies shows LyC emission at z~2.5 OIII/Hbeta=2.3 Japelj et al. (2017) Low escape fraction for bright SFGs 7% at L* and 3<z<4 At low luminosities limits are shallow 20% at 0.5L* and 60% at 0.1 L* Comparable to Grazian et al. (2017)

  46. Results on Star Forming Galaxies Rutkowski et al. (2017) 208 SFGs at z~2.5 Fesc,rel<5.6% 13 Strong emitters OIII/OII>5 Fesc,rel<14% (they are a small fraction ~6% Of the SFG population at z~2.5) Insufficient for Reionization, unless the number of emitters significantly increases at z>6

  47. HeII Reionization driven by AGNs: extended process z_AGN=5 Mean free path of HeII ionizing photons is much lower than the mfp of HI ionizing photons Compostella et al. 2014

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