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ISW

ISW. T ópicos PUC 2008. Fondo de Radiaci ón Cósmica. Fin de la época dominada por radiación. Ocurre cuando  r deja de dominar, z eq ≈3000, T eq ≈8190 o K=0.7 eV t eq ≈6.1x10 4 años Universo Euclideano dominado por materia NR. Época de Plasma.

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ISW

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  1. ISW Tópicos PUC 2008

  2. Fondo de Radiación Cósmica

  3. Fin de la época dominada por radiación • Ocurre cuando r deja de dominar, • zeq≈3000, • Teq ≈8190 oK=0.7 eV • teq ≈6.1x104 años • Universo Euclideano dominado por materia NR

  4. Época de Plasma • Inicio : 6.1x104 años (equilibrio rad-mat) • Fin : 2.1x105 años (combianción H) • Hay fotones, protones, neutrinos desacoplados y elementos livianos • Dominio materia NR y partículas cargadas, iones  Plasma • T0.3 eV • zH1300 • t2.1x105 años

  5. Época Atómica • Inicio : 2.1x105 años (combinación de H) • Fin : 2.7x105 años (desacoplo de fotones) • Hay fotones, átomos neutros, neutrinos desacoplados y pocos e- y protones Fotones se desacoplan  Fondo de radiación Cósmica Interacción dominante: e- +   + e- • Tdes0.27 eV = 3100 oK • zdes1150 • tdes2.7x105 años Fotones no volverán a interactuar con la materia

  6. Superficie de Último Esparcimiento Radiación que se observa viene de esta superficie; sin embargo, esta superficie tiene un espesor Zue  1089 z  195 z Profundidad óptica Función de visibildad = Probabilidad que un fotón sufra un escátering

  7. CMB Distortions • Global  Black Body Radiation • Directional  Anisotropies OBS. CMB z9 z198 z=0 z

  8. Global Distortions Comptonization

  9. Directional - Primary

  10. Directional - Secondary

  11. Sunyaev-Zel’dovich (SZ) clusters Coma Cluster Telectron = 108 K e- e- e- e- e- e- e- Cosmic Microwave Background e- e- X-ray Flux: Mass Optical: Redshift and Mass mm-Wave: SZ – Compton Scattering

  12. ZS Effect

  13. Directional - Tertiary • Extragalactic Radio Sources • Radio Galaxies • QSOs • Galactic Radio Sources • Dust and Gas in MW Must map these sources and subtract them from the CMB signal

  14. Sachs-Wolfe Effect CMB Photons travelling to an observer encounter metric perturbations which induce a frequency change. Metric perturbations are associated to gravitational potentials, , which are associated to density fluctuations,  redshift f i Last scattering surface blueshift  i Photon f f =f-i Density fluctuation, 

  15. Integrated SW CMB OBS. =f- i f i z

  16. Flat universe, in linear regime =cte. =cte NO ISW

  17. ≠cte • At z1.2 the universe becomes dark energy dominated and the expansion is accelerated. • ≠cte anymore • Photons get redshifted with respect to the original CMB photons • Generates a large scale anisotropy in the CMB ISW Early: Transition from  to m is not instantaneous. During teq to trec the scale factor does not change linearly  varies ISW Late: starts at the transition from m to DE

  18. The ISW f i z=0 z=1089

  19. Order of Magnitude and Scale

  20. How to detect the ISW • Given the CMB temperature resolution achieved with modern microwave explorers such as WMAP (existing) and PLANCK (future), it is possible to cross correlate the local (z<1.2) matter structure with the observed CMB structure. • The cross correlation amplitude depends on the acceleration modulus which in turn depends on the dark energy (DE) density.

  21. Cross-Correlation CMB-LSS The expectation value of density fluctuations is the cross-correlation function

  22. From a pixel map

  23. Cross Correlation CMB-LSS The ISW dominates the X-Corr. signal at angular scales   1 deg. (at smaller scale the signal is dominated by the SZ effect) Given fields A and B Legendre polynomial order l

  24. The window function of the anisotropy field, Generated by the ISW effect The window function of the galaxy field The error on each multipole

  25. The Survey Therefore, to unambiguously measure the signal, we propose a large, deep survey of galaxies. • Detect the ISW signal with S/N > 3 • Telescope: VST (2.6mt) at Paranal • Area: 5000 deg2 • Band: r band, r  23.8 • # of nights: 64 nights, 16 per year • 4 years, start 2009B ¿?  2013A • Exposure time = 240 sec.

  26. Area Layout LAYOUT

  27. Now we show that a survey with the following characteristics, • 5000 deg2 , • in one band, down to r = 23.8, • on 0.5 degrees scales and • no redshift information provides the large scale data (i.e. galaxy map) to clearly measure the ISW signal.

  28. Optimum average zS/N vs <z> • The ISW effect is driven by the accelerated expansion • Extremely distant galaxies are not affected by the accelerated expansion, so will not produce anisotropies in the CMB. CDM: m=0.3, =0.7, k=0, H0=70, w=-1

  29. Limiting Magnitude mlim=23.8

  30. Redshift Distribution, N(z)

  31. S/N()

  32. Predicted S/N() • Why 1 deg scale? • Maximize S/N • Minimize primary & secondary CMB anisotropies • SZ important at scales smaller • Optimize OmegaCam scale size.

  33. Why redshifts are not necessary Cumulative S/N(z) in redshits slices of z=0.1.  Slightly higher than the S/N with no slices

  34. Why multi-band is not necessary We only need to detect galaxies  Need one deep band • To get photometric redshifts we need at least 4 bands • Reduce the area by 4. • S/N reduces by more than 2

  35. The VST • A 2.6 m telescope • Wide Field Imaging • 16k x 16k CCD mosaic camera (Omegacam) with a 15 micron pixel, equivalent to 1 square deg. (0.21 arcsec/pixel scale) • 32 thinned CCD 2x4k (26x26 cm2)

  36. ISW@VST + ATLAS • We have designed a plan to produce results earlier than any competing survey. • The survey area will be the same as the approved ESO public survey VST ATLAS. • Arrangements have been carried out so that we provide the deep r band observations and the VST ATLAS provide a deep 120 seconds g band survey. • Having deep g and r bands in hand, a number of other programs are possible. • In addition, negotiations are in progress to add IR J and H bands with VISTA. • The finished product, in 2013, will be a deep (2 magnitudes deeper tha SDSS)

  37. Value Added Projects • Weak Lensing in the ACT Strip • The Number Density of LSB and VLSBs • Local Census of Dwarf Galaxies • Dwarf Galaxies in the Local Group • … (welcome ideas)

  38. Summary • We propose a southern 5000 deg2 deep survey of galaxies in the r band to detect the Integrated Sachs-Wolfe Effect with a signal to noise ratio 40% higher than any other survey so far (e.g. SDSS DR4) • The aim is to determine the equation of state of the universe by cross-correlating this galaxy map with high resolution CMB anisotropy maps from existing WMAP and future Planck observations. • To cover the desired field, 64 nights in 4 years (rAB . 23.8, 16 dark-grey 1.0 arcsec seeing nights per year) are required with VST • To maximize the output and open this survey to further science goals (ACT clusters, SZ effect, Red sequence galaxy clusters, LSBs, UCDs, Dwarf Galaxies, lenses) we will observe the same area as the approved VST ATLAS survey, which will provide de deep g band observations.

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