HI and Continuum Cosmology

Transcription

1 HI and Continuum Cosmology Radiometry Equation snr 1 2 A For SKA, eff S[ ] kt rms sys 1/ 2 for each 100 mjy 1/ 2 [ ] polarizati on, two polarizati ons Filipe B. Abdalla

2 Cosmology: Concordance Model Heavy elements 0.03% Neutrinos 0.3% Stars 0.5% H + He gas 4% Dark matter 20% Dark Energy 75% Outstanding questions: initial conditions (inflation?, fnl) nature of the dark matter nature of the dark energy nature of gravity at large scales value of the neutrino mass There are fluctuations at all scales but there is a preferred scale of around 1 deg.

3 Very Brief Overview on explaining the accelerated expansion Cosmological constant W=-1 Dark Energy Quintessence w=w(time) Modification of Einstein's gravity String theory Dark Energy : equation-of-state parameter w

4 The Cosmology science case back in 2004 Galaxy surveys for BAO Weak Lensing surveys BAO & WL for dark energy H0 with Masers (still very relevant!) Much has been done in the above three areas and many others since... Carilli and Rawlings 2004

5 What to look forward to: Three arrays in SKA1, SKA- Low, SKA-Mid and SKA-SUR, all of which can do some cosmology, with he specifications aside (~2019+): This baseline design can be very powerful if utilised properly but can also be optimised and this has been the topic of intense discussion over the last ~6 months SKA2 will follow having close to the original presumed capabilities of the SKA

6 Outline of cosmological science that can be done with the radio telescopes Cosmology with HI line surveys Cosmology with continuum surveys Cosmology with the EoR Cosmology with other probes

7 Power Spectrum of density fluctuations CMB experiments SDSS Galaxy Surveys

8 Sound waves in the early Universe: After recombination: Universe is neutral. Photons can travel freely past the baryons. Phase of oscillation at t rec affects late-time amplitude. Waves are frozen Wayne Hu Before recombination: Universe is ionized. Photons provide enormous pressure and restoring force. Perturbations oscillate as acoustic waves. Eisenstein

9 WMAP & SDSS fourrier space Looking back in time in the Universe CREDIT: WMAP & SDSS websites Percival et al. 06 FLAT GEOMETRY

10 Neutrino masses Neutrino masses affect the distribution of matter in the Universe, There is a free streaming length associated with the mass of the neutrino 0.05eV Neutrino Free Streaming mν 41 30eV -1 With a different neutrino mass!!! Mpc Colombi, Dodelson, & Widrow 1995 b, cdm

11 21cm: a Hydrogen Detector SPECTRAL domain to 1.4 GHz

12 What can we see with an SKA phase 1?

13 Full SKA Predictions now! What can we expect? The new corresponds to a ~10% full SKA but can be up to over sq degs, which most other surveys will not perform.

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15 Intensity mapping results to date: Cross correlations with optical galaixes (Masui et al.) Auto correlations also detected (Switzer et al.) Foreground subtraction and polarisation purity are issues! Projects are planning to map this better in the advent of the SKA: Chimes, Tianlai, Bingo... The SKA could (depending on configuration) do a huge amount of such studies.

16 If we degrade the resolution to the binning we will do anyway: Collect signal from all HI in that bin, obtain a spectrum. Mean signal will be from the mean HI content of that shell Fluctuations will be related to the large scale structure. Wolz et al. To be submitted

17 Foreground subtraction.

18 Intensity mapping Theoretical Model of the power spectrum Cl Statistically speaking SKA w intensity mapping can measure fnl/modified gravity to a gret accuracy. Depends on cosmological parameters like (Omegam;w0; b; fnl) Contours are biased towards a different best fit when systematics are included BAO fit is not biased. (Wolz et al.)

19 Measurements of the expansion rate: Do a LSS experiment 10 years apart! Average measurements of the frequency of HI for ensemble of galaxies could measure the expansion rate directly: high timelines are needed, ~0.1cm/s/yr accuracy over ~10 yrs. CODEX like experiment H. Klockner (German white paper).

20 Continuum surveys with radio telescopes No redshifts but many more galaxies

21 Measuring inflation parameters with galaxy surveys

22 Measuring non Gaussianity with Radio surveys -> different potentials will create gaalxies at different rates/positions fnl is one (of several) parameters telling us about primordial non-gaussian PDF for fluctuations - early Universe physics from (Bacon & Racanelli).

23 The integrated Sach-Wolf effect! From D. Bacon.

24 Modified gravity Standard Model Interactions confined to 4D brane Gravity roams the 5D bulk - leaks DGP f(r) models Illustrative example Modified DGP (mdgp) Dvali and Turner (2003) Infinite extra dimensions motivate the modification and parameterisation of the Friedmann equation Is this the right plot? LCDM (w_0 = -1) DGP (w_0 = w_a = 0.32) mdgp specifies varying expansion histories. They are, however, degenerate with arbitrary dark energy models

25 Growth of structure Two perturbation/metric potentials in the Newtonian Gauge This is the Poisson equation DGP GR Koyama (06) DGP GR gives us linear growth equations

26 Continuum counts Continuum surveys will find a wealth of galaxies in high numerb density compared to line emission surveys. Several probes can be used: galaxy correlations, ISW, cosmic magnifiction. Pathfinders will be able to provide good constraints. Good redshift distribution knowledge will be very important. Photo-z form optical surveys might improve further these constraints Raccanelli et al. 10

27 Das Bild kann zurzeit nicht angezeigt werden. Das Bild kann zurzeit nicht angezeigt werden. Das Bild kann zurzeit nicht angezeigt werden. Das Bild kann zurzeit nicht angezeigt werden. Background sources Dark matter halos Observer Statistical measure of shear pattern, ~1% distortion Radial distances depend on geometry of Universe Foreground mass distribution depends on growth of structure

28 Das Bild kann zurzeit nicht angezeigt werden. Das Bild kann zurzeit nicht angezeigt werden. Das Bild kann zurzeit nicht angezeigt werden. Das Bild kann zurzeit nicht angezeigt werden. Background sources Dark matter halos Observer Statistical measure of shear pattern, ~1% distortion Radial distances depend on geometry of Universe Foreground mass distribution depends on growth of structure

29 Cosmic shear two point tomography Credit S. Bridle

30 Cosmic shear two point tomography Credit S. Bridle

31 Cosmic shear two point tomography Credit S. Bridle

32 Intrinsic alignements. What we measure Cosmic shear Additional contributions

33 Measuring weak lensing and shapes in the radio ~microjy would yield ~5 gals per sq arcmin Around 5000 sq degs might be possible with a psf of 0.5 with SKA-1 depending on configurations Psf should be well behaved depending on tapering of visibilities Pattel et al. submitted

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36 Better systematic effects: Color dependent shapes. This is not an issue for radio if we have the correct signal to noise to check this systematic If we assume that weighting can be tweaked for this to be checked, the signal to noise might drop enough so that the science is at risk

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38 21 cm basics HI hyperfine structure 1 1 S 1/2 1 0 S 1/2 n 1 n 0 =21cm Use CMB backlight to probe 21cm transition T T S T K HI T b n 1 /n 0 =3 exp(-h 21cm /kt s ) z=13 f 21cm =1.4 GHz z=0 f obs =100 MHz 3D mapping of HI possible - angles + frequency 21 cm brightness temperature 21 cm spin temperature Coupling mechanisms: Radiative transitions (CMB) Collisions 38 Wouthuysen-Field

39 The Epoch of reionization: MHz (z ~ 20-6) - When did the first objects form? - What was the matter distribution like at such early times? - What reionized the Universe?

40 21 cm fluctuations Brightness temperature Baryon Density Neutral fraction Gas Temperature W-F Coupling Velocity gradient b Cosmology Reionization X-ray sources Ly sources Cosmology Dark Ages Twilight Pritchard

41 Extraction of the signal with LOFAR & SKA! LOFAR EoR windows. Haslam 408MHz The Galaxy is times brighter than the signal sought Chapman, FBA et al 2012a Chapman, FBA et al 2012b Real signal Reconstruction Use methods, e.g. the cocktail party problem solution, and wavelet decomposition in order to separate the galaxy from the signal

42 Returning to reionisation: Redshift space disortions: Barkana & Leob 10 Mao et al

43 SKA and LOFAR might be able to measure this power spectrum. With RSD s cosmology can be probed... Mao et al

44 Cosmology with galaxy clusters Not much has been done in terms of cosmology specifically with the SKA, but much has been done in terms of property studies (Ferrari) might want to be refreshed (Battye, Davies & Weller, 05).

45 Conclusions The SKA will be competitive in several probes for cosmology. In the past 9 years several new areas have been investigated to enhance potential HI and continuum cosmology Intentity mapping Cosmology from weak lensing Counts, in HI and continuum Cosmology form the EoR It will be important to have systematic in hand and this is where the combination of surveys.