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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.

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Probing dark matter clustering using the Lyman-  forest

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

  2. 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

  3. Ly-alpha forest SDSS quasar spectrum simulation of the IGM (25 Mpc/h, neutral hydrogen) (R. Cen) z = 3.7 quasar

  4. Absorption by gas at redshift z appears in a quasar spectrum at wavelength

  5. Scales of various LSS probes (figure by Max Tegmark)

  6. WMAP CMB map

  7. WMAP CMB power spectrum

  8. SDSS Galaxies - for the LyaF we are looking in between (not literally - at high redshift)

  9. SDSS galaxy power spectrum (Tegmark et al. 2004)

  10. CFHTLS cosmic shear correlation function (Hoekstra et al. 2005)

  11. QSO spectrum at z=3 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

  12. HIRES Spectra transmitted flux fraction Z~2 Z~3 Z~4

  13. LyaF power from SDSS (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

  14. What is the LyaF good for? • ~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)

  15. SDSS LyaF Data 3300 spectra with zqso>2.3 redshift distribution of quasars 1.4 million pixels in the forest redshift distribution of Ly forest pixels

  16. SDSS quasar spectra • 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

  17. Compute statistics of the transmitted flux fraction, 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

  18. LyaF power from SDSS (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

  19. Ly-alpha forest as a tracer of mass/dark matter 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)

  20. Best fitted model • 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

  21. Linear Power Spectrum Constraint(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

  22. Basic linear power spectrum constraint from the LyaF:

  23. Comprehensive cosmological parameter paper: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

  24. WMAP vs. LyaF (vanilla 6 parameters)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

  25. WMAP vs. LyaF (including running)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

  26. Warm Dark Matter constraintsSeljak, 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

  27. The measured 1D power spectrum is equal to 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.

  28. Black: CDM, Red: WDM • Easy to see by eye… and we have almost 50000 chunks of this length.

  29. Warm Dark Matter constraintsSeljak, 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)

  30. WDM constraints • ~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)

  31. PBH dark matter constraintsAfshordi, McDonald, & Spergel (2003) • Linear theory power. • Primordial black hole dark matter leads to extra white noise power, increasing with increasing mass of the holes.

  32. PBH dark matter constraintsAfshordi, 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.

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