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Simona Gallerani (Osservatorio Astronomico di Roma)

What can we learn from quasar spectra on the high-redshift Universe?. Simona Gallerani (Osservatorio Astronomico di Roma). In collaboration with: T.Choudhury, P. Dayal, X. Fan, A. Ferrara, A. Maselli, R. Maiolino, R. Salvaterra. 21 th July 2009 Roman Young Researchers Meeting.

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Simona Gallerani (Osservatorio Astronomico di Roma)

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  1. What can we learn from quasar spectra on the high-redshift Universe? Simona Gallerani (Osservatorio Astronomico di Roma) In collaboration with: T.Choudhury, P. Dayal, X. Fan, A. Ferrara, A. Maselli, R. Maiolino, R. Salvaterra 21th July 2009Roman Young Researchers Meeting

  2. THE COSMOLOGICAL PRINCIPLE The Universe is homogeneous and isotropic on large scales Cosmic Microwave Background The early Universe ~50 kyr The Universe is composed by a very hot and dense mix of particles and radiation Today Big Bang The expansion allows the radiation to decouple from matter and the first atoms to form Recombination process

  3. Cosmic Web First stars and galaxies originated predominantly in the regions of intersection of these filaments. They are immersed in the Intergalactic medium (IGM) The first stars

  4. Cosmic reionization ~100 Myr ≤1 Gyr ~14 Gyr Overlap stage Post-overlap stage Pre-overlap stage What is the epochof reionization (EOR)?

  5. Quasars: a class of very bright Active Galactic Nuclei Black Hole Accretion disk Particularly luminous in the rest frame near ultra-violet, i.e. close to the Lyα emission line Dust torus The quasar spectra we observe are strongly affected by the intervening material along the lines of sight

  6. The Lyα forestinquasar absorption spectra α=1216 Å Keck telescope REDSHIFT

  7. Fan et al. (2005) QSOs constraints on cosmic reionization SDSS ~20 QSOs @ 5.7<z<6.4 Becker et al. (2003)

  8. Density field Log-Normal model (ΛCDM) Coles & Jones (1991) Neutral hydrogen Reionization model (TIGM; UVB) Choudhury & Ferrara (2006) Simulating the Ly forest Optical depth (Voigt profile)

  9. Reionization models Early Reionization (ERM) Late Reionization (LRM)

  10. ERM LRM Models testing Transmitted flux Optical depth evolution Fan et al. (2006) Songaila (2004) Fan et al. (2002)

  11. GAPS Simulated spectra

  12. Largest gap width distribution Observations vs Simulations Low Redshift (zem<6) High Redshift (zem>6) SG, Ferrara, Fan, Choudhury (2007) ERM LRM LRM ERM The Universe is highly ionized at z~6

  13. Quasars: a class of very bright Active Galactic Nuclei Black Hole Accretion disk Particularly luminous in the rest frame near ultra-violet, i.e. close to the Lyα emission line Dust torus The quasar spectra we observe are strongly affected by the intervening material along the lines of sight AND BY THE DUST SURROUNDING THE AGN!

  14. Dust extinction on quasar spectra Intrinsic spectrum Dust absorbed spectrum Dust absorbs preferentially bluer photons, thus reddening the spectra

  15. An example of extincted spectra at z~6

  16. An empirical extinction law for the high redshift dust

  17. Conclusions Quasar absorption spectra provide a huge amount of information both concerning the ionization level of the intergalactic medium and the amount of dust present in the host galaxy. The analysis of ~ 20 quasars at z~6 shows thatobservations are consistent with a highly ionized intergalactic medium at z~6. The analysis of ~ 30 quasars at 4<z<6 shows that the properties of dust at these epochs differ from the local Universe.

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