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Probing dark matter clustering using the Lyman-  forest. Pat McDonald (CITA) COSMO06, Sep. 28, 2006.

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Probing dark matter clustering using the lyman forest

Probing dark matter clustering using the Lyman- forest

Pat McDonald

(CITA)

COSMO06, Sep. 28, 2006


Probing dark matter clustering using the lyman forest

The Lyman- forest is the Ly absorption by neutral hydrogen in the intergalactic medium (IGM) observed in the spectra of high redshift quasarsA probe of (relatively small-scale) large-scale structure


Probing dark matter clustering using the lyman forest

Ly-alpha forest

SDSS quasar

spectrum

simulation of the IGM

(25 Mpc/h, neutral hydrogen)

(R. Cen)

z = 3.7 quasar



Scales of various lss probes
Scales of various LSS probes at wavelength

(figure by

Max Tegmark)


Wmap cmb map
WMAP CMB map at wavelength




Sdss galaxy power spectrum tegmark et al 2004
SDSS galaxy power spectrum literally - at high redshift)(Tegmark et al. 2004)


Cfhtls cosmic shear correlation function hoekstra et al 2005
CFHTLS cosmic shear correlation function literally - at high redshift)(Hoekstra et al. 2005)


Keck hires quasar spectrum

QSO spectrum at z=3 literally - at high redshift)

Keck-HIRES Quasar Spectrum

  • Neutral hydrogen

  • Lyman- absorption at  < 1216 (1+zq) Å

  • Metal absorption small but everywhere

  • Continuum fluctuations significant on large scales

  • From Rauch & Sargent or Cowie


Hires spectra
HIRES Spectra literally - at high redshift)

transmitted flux fraction

Z~2

Z~3

Z~4


Lyaf power from sdss mcdonald et al 2006
LyaF power from SDSS literally - at high redshift)(McDonald et al. 2006)

  • 2(k) = π-1 k P(k)

    (0.01 s/km ~ 1 h/Mpc)

  • Colors correspond to redshift bins centered at z = 2.2, 2.4, …, 4.2 (from bottom to top)

  • 1041<rest<1185 Å

  • Computed using optimal weighting

  • Noise subtraction

  • Resolution correction

  • Background subtraction using regions with rest>1268 Å

  • Error bars from bootstrap resampling

  • Code tested on semi-realistic mock spectra

  • HIRES/VLT data probes smaller scales


What is the lyaf good for
What is the LyaF good for? literally - at high redshift)

  • ~100 kpc/h scales

    • Warm dark matter

      • Gravitinos

      • Sterile neutrinos

      • “Dark matter from decays” (Kaplinghat)

    • Primordial black holes

  • ~1 Mpc/h scales

    • Inflation: running spectral index

    • Light neutrino masses

    • “Late forming dark matter in theories of neutrino dark energy”?(Weiner)

  • >10 Mpc/h scales

    • Dark energy & curvature: baryonic acoustic oscillations (future, McDonald & Eisenstein 2006)


Sdss lyaf data
SDSS LyaF Data literally - at high redshift)

3300 spectra with zqso>2.3

redshift distribution of quasars

1.4 million pixels in the forest

redshift distribution of Ly forest pixels


Sdss quasar spectra
SDSS quasar spectra literally - at high redshift)

  • Resolution typically 160 km/s (FWHM)

  • Pixel size 70 km/s

  • We use spectra with S/N>1, with a typical S/N≈4 (per pixel)

  • This is an unusually good one


Probing dark matter clustering using the lyman forest

Compute statistics of the transmitted flux fraction, literally - at high redshift)F(z)=exp(-), i.e., the spectrum after dividing by an estimate of the quasar continuum

  • Use rest wavelength range 1041<rest<1185 Å

  • Mean absorption ‹F(z)›

  • Power spectrum of fluctuations around the mean F(z) = F(z)/ ‹F(z)›-1


Lyaf power from sdss mcdonald et al 20061
LyaF power from SDSS literally - at high redshift)(McDonald et al. 2006)

  • 2(k) = π-1 k P(k)

    (0.01 s/km ~ 1 h/Mpc)

  • Colors correspond to redshift bins centered at z = 2.2, 2.4, …, 4.2 (from bottom to top)

  • 1041<rest<1185 Å

  • Computed using optimal weighting

  • Noise subtraction

  • Resolution correction

  • Background subtraction using regions with rest>1268 Å

  • Error bars from bootstrap resampling

  • Code tested on semi-realistic mock spectra

  • HIRES/VLT data probes smaller scales


Probing dark matter clustering using the lyman forest

Ly-alpha forest as a tracer of mass/dark matter literally - at high redshift)

Basic model: neutral hydrogen (HI) density is determined by ionization equilibrium between recombination of e and p and HI ionization by a nearly uniform UV background, this gives

Recombination coefficient depends on gas temperature

Neutral hydrogen traces overall gas distribution, which traces dark matter on large scales, with additional pressure effects on small scales (parametrized by the filtering scale kF)


Best fitted model
Best fitted model literally - at high redshift)

  • 2 ≈ 185.6 for 161 d.o.f.

  • A single model fits the data over a wide range of redshift and scale

  • Wiggles from SiIII-Ly cross-correlation

  • Helped some by HIRES data


Linear power spectrum constraint for lcdm like power spectrum
Linear Power Spectrum Constraint literally - at high redshift)(for LCDM-like power spectrum)

1, 2, and 3-sigma error contours for the amplitude and slope of the linear power spectrum at z=3.0 and k=0.009 s/km



Comprehensive cosmological parameter paper seljak slosar mcdonald astro ph 0604335
Comprehensive cosmological parameter paper: literally - at high redshift)Seljak, Slosar, & McDonald astro-ph/0604335

  • CMB: WMAP3, Boomerang-2k2, CBI, VSA, ACBAR

  • Galaxies: SDSS-main, SDSS-LRG (BAO), 2dF

  • SN: SNLS, Riess et al.

  • LyaF: SDSS, HIRES


Wmap vs lyaf vanilla 6 parameters linear amp slope constraints at z 3 k 0 009 s km
WMAP vs. LyaF (vanilla 6 parameters) literally - at high redshift)Linear amp. & slope constraints at z=3, k=0.009 s/km

  • Green: LyaF

  • Red: WMAP

  • Black: WMAP, SDSS-main, SN

  • Yellow: All

  • Blue: Viel et al. (2004) independent LyaF


Wmap vs lyaf including running linear amp slope constraints at z 3 k 0 009 s km
WMAP vs. LyaF (including running) literally - at high redshift)Linear amp. & slope constraints at z=3, k=0.009 s/km

  • Green: LyaF

  • Red: WMAP

  • Black: WMAP, SDSS-main, SN

  • Yellow: All

  • Blue: Viel et al. (2004) independent LyaF


Warm dark matter constraints seljak makarov mcdonald trac astro ph 0602430
Warm Dark Matter constraints literally - at high redshift)Seljak, Makarov, McDonald, & Trac, astro-ph/0602430

  • Free-streaming erases power on small scales.

  • Simulate the LyaF power for different sterile neutrino masses:

  • 6.5 keV, 10 keV, 14 keV and 20 keV

  • (1.3, 1.8, 2.4, 3.1 keV for traditional WDM)

  • At higher z, linear signal largely preserved


Probing dark matter clustering using the lyman forest

The measured 1D power spectrum is equal to literally - at high redshift)

the 3D power spectrum integrated over the transverse

k’s. This means that the 1D power is sensitive to

smaller scales than one would guess from

k_parallel.


Black cdm red wdm
Black: CDM, literally - at high redshift)Red: WDM

  • Easy to see by eye… and we have almost 50000 chunks of this length.


Warm dark matter constraints seljak makarov mcdonald trac astro ph 06024301
Warm Dark Matter constraints literally - at high redshift)Seljak, Makarov, McDonald, & Trac, astro-ph/0602430

  • Flux power spectrum

  • 3000+ SDSS spectra

  • HIRES data probes smaller scales

  • 2(k) = π-1 k P(k)

  • 0.01 s/km ~ 1 h/Mpc

  • Colors correspond to redshift bins centered at z = 2.2, 2.4, …, 4.2 (from bottom to top)


Wdm constraints
WDM constraints literally - at high redshift)

  • ~Model independent: 50% power suppression scale restricted to k>18 h/Mpc (Gaussian rms smoothing ~<45 kpc/h)

  • Thermal relic (gravitino): mass>2.5 keV

  • Sterile neutrino: mass>14 keV

  • Agreement with other main LyaF group led by Viel (>~11 keV)


Pbh dark matter constraints afshordi mcdonald spergel 2003
PBH dark matter constraints literally - at high redshift)Afshordi, McDonald, & Spergel (2003)

  • Linear theory power.

  • Primordial black hole dark matter leads to extra white noise power, increasing with increasing mass of the holes.


Pbh dark matter constraints afshordi mcdonald spergel 20031
PBH dark matter constraints literally - at high redshift)Afshordi, McDonald, & Spergel (2003)

  • Simulated LyaF power for different masses.

  • Found M~<20000 M_sun

  • These results were pre-SDSS.

  • Working on improving them by ~ an order of magnitude.