Was the universe neutral beyond redshift six? Simona Gallerani - - PowerPoint PPT Presentation

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Was the universe neutral beyond redshift six? Simona Gallerani - - PowerPoint PPT Presentation

Feb 09, 2024 216 likes •491 views

Was the universe neutral beyond redshift six? Simona Gallerani SISSA, Trieste, Italy In collaboration with: A. Ferrara; X. Fan; T. Choudhury; R. Salvaterra QSO spectra at high redshift GAPS GAPS 1 / 2 3 / 2 2 2 h h 1 z

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SLIDE 1

Simona Gallerani

SISSA, Trieste, Italy

Was the universe neutral beyond redshift six?

In collaboration with: A. Ferrara; X. Fan; T. Choudhury; R. Salvaterra

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SLIDE 2

QSO spectra at high redshift

Becker et al. 2003

What can we learn from these observables?

Fan et al. 2005

GAPS GAPS PEAKS PEAKS

2 / 3 2 2 / 1 2 5

7 1 02 . 13 . 10 9 . 4 ) (

  • +
  • =
  • z

x h h z

HI b m GP

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SLIDE 3

Simulating the Ly forest

  • ptical depth

at the Ly transition

dl nHI

Ly

  • =
  • )

(

Neutral hydrogen distribution Baryonic density field

Coles & Jones (1991)

Log-Normal model IGM ionization state Reionization model

Choudhury & Ferrara (2005/2006)

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SLIDE 4

Reionization models

EARLY REIONIZATION (ERM) LATE REIONIZATION (LRM)

Volume Filling Factor Photo-Ionization Rate

ERM LRM Data from McDonald & Miralda-Escude’(2001); Bolton etal. (2005/2007); Fan etal. (2006) ERM LRM

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SLIDE 5

Simulated spectra

GAPS GAPS

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SLIDE 6

Largest gap width distribution

Observations vs Simulations

Low Redshift (zem<6) ERM LRM SG, Ferrara, Fan, Choudhury (arXiv:0706.1054) High Redshift (zem>6) LRM ERM

5

10 8

  • HI

x

6 . 5 = z

HR

Fan et al 2006

  • This work

6 . 5 = z 3 . 5 = z

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SLIDE 7

Largest gap width distribution

Observations vs Simulations

5

10 6

  • HI

x

5

10 4

  • HI

x

6 . 5 = z 3 . 5 = z

SG, Ferrara, Fan, Choudhury (arXiv:0706.1054)

xHI<0.36 @ z=6.3

Low Redshift (zem<6) High Redshift (zem>6)

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SLIDE 8

Simulated spectra

PEAKS PEAKS

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SLIDE 9

Transmissivity windows

What is the origin of the peaks? Cosmic underdense regions

  • GAP

1

  • PEAK

1 .

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SLIDE 10

Largest peak width distribution

Observations vs Simulations

High Redshift (zem>6) Low Redshift (zem<6)

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SLIDE 11

Transverse proximity effect: OBSERVATIONS

Mahabal et al (2005) Fan et al (2006) QSO1

RD J1148+5252

7 . =

  • R

7 . 5 =

em

z 3 . 24

  • =

B

M Mpc

QSO2

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SLIDE 12

Transverse proximity effect: SIMULATIONS

1 55 2

10 4 ln ) ( 4

  • =

=

  • +
  • =
  • s

N d R N

HI

QSO QSO bkg TOT

  • &

&

HII Regions

(case B)

Underdense Regions

(case A)

Peaks origin:

SG, Ferrara, Fan, Choudhury (arXiv:0706.1054)

Peak Spectral Density

OUT IN

PSD PSD

  • 3
  • d

dN PSD

peaks

=

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SLIDE 13

Transverse proximity effect: first detection OBSERVATIONS vs SIMULATIONS

= R R Mpc R 4

  • c

R R tQ

  • >
  • Myr

18

  • R
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SLIDE 14

GAPS GAPS

Summary

Current observational data do not require any sudden change in the IGM ionization state @ z~6.

  • The neutral hydrogen fraction xHI evolves smoothly from

10-4.4 @ z=5.3 to 10-4.2 @ z=5.6; xHI<0.36 @ z=6.3

  • Further high-z observations are required to constrain zrei.

The comparison with data favors zrei 7.

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SLIDE 15

PEAKS PEAKS

Summary

First detection of HI transverse proximity effect towards SDSS J1148+5251 (zem=6.42).

  • Observed peaks are much larger than simulated ones.
  • Lower limit on the foreground QSO lifetime
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SLIDE 16

Additional lighthouses:GRBs

GRBs time-variability allows to a multiple sampling of the same LOS. Afterglow spectra follow a power-law (easier continuum determination). GRBs are soon expected to be found at redshifts higher than QSOs ones.

[GRB 050904 @ z=6.29 (Kawai et al. 2006)]

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SLIDE 17

GRBs absorption spectra

Largest dark gap 5 d 3 d 1 d 0.3 d 0.2 d 0.1 d

ERM LRM P r e l i m i n a r y r e s u l t s

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SLIDE 18

Time evolution of the dark gaps

GRB 050904 (Kawai et al. 2006)

P r e l i m i n a r y r e s u l t s

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SLIDE 19

P r e l i m i n a r y r e s u l t s

Largest gap probability isocontours

80 40

max

W

Å

120 80

max

W

Å

60% 45% 30% 15% 15% 30% 45%

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SLIDE 20

Conclusions

QSOs and GRBs absorption spectra favor an epoch of reionization zrei7

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SLIDE 21
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SLIDE 22
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SLIDE 23

Unwarranted assumptions

Photoionization equilibrium deviations: SHOCKS Uniform UVB

WORK IN PROGRESS

H rec

t t >

2 / 3

5 . 6 ) 1 ( 5 . 7

  • +

<

  • z

noeq HI eq HI

x x >

UVB fluctations at z3

(Maselli & Ferrara 2003; Bolton & Haehnelt2003)

) (

  • =
  • uniform

RT

  • >
  • In low density regions
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SLIDE 24

QSO2 QSO1

7 . 5 =

em

z 42 . 6 =

em

z

  • R
  • R

time

) (

  • t

t c R R tQ

  • +
  • >
  • Myr

18

  • t

c R t t t

Q start

  • =

+

  • t

c R t tstart

  • =
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SLIDE 25

Current Current data data do do not require not require any sudden change change in the IGM ionization ionization state @ z state @ z~ ~6 6. Observations favour a fully ionized Universe fully ionized Universe @ z @ z~ ~6 6. HII HII region size region size measurement strongly overestimate x

  • verestimate xHI

HI

if the apparent shrinking effect apparent shrinking effect is not taken into account. RT RT simulations simulations are needed to simulate QSO HII QSO HII regions regions. .

Conclusions

6

  • z

@

PART I PART II