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THE LYMAN-a FOREST AS A PROBE OF
FUNDAMENTAL PHYSICS
MATTEO VIEL

• Cosmological significance of the Lyman-a forest
• 2. LUQAS The observational sample
• Hydro-dynamical simulations of the Lyman-a forest
• Cosmological parameters Implications for
  inflation,
• neutrinos, gravitinos, warm dark matter
  particles

With M. Haehnelt, J. Lesgourgues, S. Matarrese,
A. Riotto, V. Springel, J. Weller
Shanghai, 16 March 2005
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GOAL the primordial dark matter power
spectrum
CMB physics z 1100 dynamics
Continuum fitting
Lya physics z lt 6 dynamics
termodynamics
Temperature, metals, noise
Tegmark Zaldarriaga 2002
CMB Lyman a
Long lever arm
Relation P FLUX (k) - P MATTER (k) ??
Constrain spectral index and shape
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the WMAP era
before WMAP Croft et al. 2002
Tilt in the spectrum nlt1 ? Running
spectral index dn/dlnk lt 0 ?
WMAP Verde et al. 2003
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Wm 0.26 WL 0.74 Wb0.0463 H 72 km/sec/Mpc
- 60 Mpc/h COSMOS computer DAMTP
(Cambridge)
DM
GAS
STARS
NEUTRAL HYDROGEN
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The LUQAS sample -I
Large sample Uves Qso Absorption Spectra (LP-UVES
program P.I. J. Bergeron) high resolution 0.05
Angstrom, high S/N gt 50 low redshift, ltzgt2.25,
Dz 13.75
Nr. spectra
redshift
Kim, MV, Haehnelt, Carswell, Cristiani, 2004,
MNRAS, 347, 355
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The LUQAS sample II systematic errors

Effective optical depth
Low resolution SDSS like spectra
High resolution UVES like spectra
ltFgt exp (- t eff) Power spectrum of
F/ltFgt
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Hydro-simulations scalings
T T0 ( 1 d) g-1
P FLUX (k) b2(k) P MATTER (k)
Effective optical depth
Viel, Haehnelt, Springel, MNRAS, 2004, 354, 684
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Hydro-simulations what have we learnt? Many
uncertainties which contribute more or less
equally (statistical error is not an issue!)
ERRORS
CONTRIBUTION TO
FLUCT. AMPL.
Statistical error 4
Systematic errors 15
t eff (z2.125)0.17 0.02 8
t eff (z2.72) 0.305 0.030 7
g 1.3 0.3 4
T0 15000 10000 K 3
Method 5
Numerical simulations 8
Further uncertainties 5
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Cosmological implications combining the forest
data with CMB - I
MV, Haehnelt, Springel 2004
SDSS Seljak et al. 2004
n 1.01 0.02 0.06 s8 0.93 0.03
0.09
Systematic error
Statistical error
Note that the flux bispectrum analysis agrees
with these values MV, Matarrese, Heavens,
Haehnelt, Kim, Springel, Hernquist, 2004
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Cosmological implications combining the forest
data with CMB - II
MV, Weller, Haehnelt, MNRAS, 2004, 355, L23
s8 0.93 0.07 n0.99 0.03
d ns/ d ln k
SDSS Seljak et al. 2004
s8 0.90 0.03 n0.98 0.02 nrun
-0.003 0.010 nrun-0.033 0.025
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Cosmological implications constraints on
slow-roll inflation - III
MV, Weller, Haehnelt, MNRAS, 2004, 355, L23
V inflaton potential
T/S
r lt 0.45 (95 lim.)
r 0.50 0.30 No evidence for
gravity waves
SDSS Seljak et al. 2004
T/S
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Cosmological implications Warm Dark Matter
particles-I
LCDM
WDM 0.5 keV
30 comoving Mpc/h z3
In general
if light gravitinos
k FS 5 Tv/Tx (m x/1keV) Mpc-1
k FS 1.5 (m x/100eV) h/Mpc
Set by relativistic degrees of freedom at
decoupling
MV, Lesgourgues, Haehnelt, Matarrese, Riotto,
PRD in press
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Cosmological implications Warm Dark Matter
particles-II
LWDM
LCWDM (gravitino like)
W gravitino/ W DM
Scale of free streaming
Set limits on the scale of Supersymmetry
breaking L susy lt 260 TeV
m WDM gt 550 eV gt 2keV sterile
neutrino lt 16 eV gravitino
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Cosmological implications constraints on
neutrinos
WMAP 2dF Lyman-a
S mn (eV) 0.33 0.27
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HPM simulations of the forest
Full hydro 2003 part.
HPM PMGRID600 HPM
PMGRID400
FLUX POWER
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HIGH RESOLUTION HIGH S/N vs
LOW RESOLUTION LOW S/N
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LUQAS vs SDSS
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SUMMARY

• LUQAS a unique high resolution view on the
  Universe at z2.1
• 2. Hydro-dynamical simulations of the Lyman-a
  forest. Systematic
• Errors? Differences between hydro codes?
• Cosmological parameters no fancy things going on
  
• s8 0.93 n 1 no running
• substantial agreement between SDSS and LUQAS but
  SDSS has
• smaller error bars not because of the larger
  sample but because of
• the different theoretical modelling
• Constraints on inflationary models, neutrinos
  and WDM

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HPM simulations of the forest-I
equation of motion for gas element
if T T0 ( 1 d) g-1
Gnedin Hui 1998
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Feedback effects Galactic winds
No Feedback
Feedback
Density
Temperature

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Feedback effects Galactic winds-III
Line widths distribution
Column density distribution function
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Metal enrichment CIV systems at z3
Strong Feedback e1 ---- Role of the UV background
Mori, Ferrara, Madau 2000 Rauch, Haehnelt,
Steinmetz 1996 Schaye et al. 2003
Soft background ---- Role of different feedback
e0
e1
e0.1
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