Radio Cosmology Tzu-Ching Chang (ASIAA) Wednesday, June 5, 2013
Cosmology in the Planck era ESA Planck (flat Λ CDM): Ho=67.95 ± 1.5 km/s/Mpc Wednesday, June 5, 2013
Cosmology from Planck A flat Λ CDM provides a very good fit to Planck data. The Planck calibrated Λ CDM predictions: Agree perfectly with BAO data at lower redshifts Disagree mildly (~2.5 σ ) with the most precise direct H 0 measurements (e.g., HST Key project, Cepheids+SN). Neutrinos background detected (N eff = 3.36 ± 0.34) CMB lensing is playing an important role in the constraints, particularly on the sum of neutrino masses. Data are consistent with simplest inflation models No detected signature of primordial non-Gaussianities (f nl = 2 ± 5) Spectral index: n=0.9608 ± 0.0054 (7 σ deviation from n=1). Wednesday, June 5, 2013
Cosmology post Planck Is it still interesting? Not end of story - we still don’t know the initial conditions, dark matter, and dark energy. Need to nail parameters with Large-Scale Structure surveys Dark energy (for wCDM, best probe at z<2). Curvature (LSS geometry probes): d k < 10 -3 ? Sum of neutrino mass (damping of p(k)): dE < 0.01eV Non-gaussianity (scale-dependent bias): df nl < 1? Wednesday, June 5, 2013
Large-scale structure probes Besides (next generation) CMB polarization, actions are in LSS. CMB: ~2D information, mode # ∝ (l max ) 2 LSS redshift surveys: 3D information, mode # ∝ (k max ) 3 shot noise dominates p(k) at high wavenumber k shot noise ~ 1/n_gal n_gal = 10 -4 h 3 Mpc -3 (SDSS, WiggleZ) n_gal = (3-5) x 10 -4 h 3 Mpc -3 (BOSS, HETDEX, HSC, PFS) n_gal = 10 -3 h 3 Mpc -3 (Euclid, LSST, SKA) Wednesday, June 5, 2013
What can (low-freq) radio do? Emission v.s. absorption (21-cm forests; difficult. see Hiroyuki Hirashita’s talk) Continuum emissions “thresholded”: radio continuum sources (e.g., FIRST, NVSS, EMU, MIGHTEE, WODAN surveys. Owen & Morrison 08, Condon+ 12) “non-thresholded”: radio background intensity and fluctuations (e.g. ARCADE-2, Fixsen+ 09) Line emissions (in particular, HI 21cm) “thresholded”: “SKA: billions of HI galaxies at z>1” (e.g., Verheijen+ 10, Fernandez+ 13). MeerKAT and ASKAP surveys. Gas and galaxy evolution. “non-thresholded”: 21cm Intensity Mapping (e.g., Chang+ 08, 10, Masui+ 13, Switzer+ 13) for LSS; Reionization probes. Wednesday, June 5, 2013
Continuum Surveys Weak Lensing by large-scale structure (Cosmic Shear) Measures both the growth factor G(z) and the geometry D A (z). Hetdex Motivates many dark energy surveys: CFHT-LS, DES, Subaru- HSC, Euclid Systematics for shape measurements are challenging, in particular the PFS for ground-based optical surveys is an issue Radio interferometric has deterministic PFS and can be illuminating. However, dn/dz needs to be measured/modelled. FIRST measurement (Chang+ 04); EMU, MIGHTEE, WODAN upcoming for dark energy measurements (e.g., Patel+ 10). Magnification lensing may be feasible if dn/dz is known. Wednesday, June 5, 2013
Continuum Surveys Integrated Sachs-Wolfe effect (ISW) Granett, Neyrinck & Szapudi Sensitive to gravitational potential decay on large-scales, e.g., when dark energy dominated at low-z. Requires all-sky LSS x CMB surveys (e.g., NVSS x WMAP , Nolta+ 05). Cosmic-variance limited, at most a 7 σ signal. Upcoming radio surveys for modified gravity, dark energy tests (e.g., Raccanelli+08, 12; Dupe+10 review). Wednesday, June 5, 2013
21cm emission on galaxy scales 10 h 02 m 23 s 10 h 00 m 23 s z=0.176 M=8.0 x 10 M z=0.121 M=3.9 x 10 M 800 0.187 600 0.130 D L (Mpc) t f i h s d e z=0.029 M=1.2 x 10 M R 400 0.089 z=0.076 M=6.6 x 10 ; 6.4 x 10 M 200 0.046 Fernandez+13 Pilot JVLA HI survey of the COSMOS field HI morphology is a great tool for merger interaction study Wednesday, June 5, 2013
21cm Cosmology HI 21cm radiation observable up to z~150. Probes 3D structure of the Universe, accessible via Intensity Mapping EoR Up to 10 16 modes to z~50 (Hubble/Jeans scale) 3 . Fundamental Physics: probes of LSS geometry LSS and growth of structure, via Lensing, BAO, AP SDSS III Astrophysics: EoR, galaxy formation & evolution Experiments Now EoR: GMRT-EoR, PAPER, LOFAR, MWA, 21CMA, EDGES, DARE LSS: GBT, CRT, CHIME Tegmark & Zaldarriaga 08 SKA1 can tackle both redshift windows. Wednesday, June 5, 2013
21cm Intensity Mapping Measure HI associated with large-scale structure instead of with galaxies (Wyithe & Loeb 08, Chang+08, Seo+10). CMB-like, but measure 3D temperature fluctuations. Low angular resolution, high spectral/redshift resolution. Provides a broad redshift window (0< z < 25) and offers an economical way for a powerful LSS survey. Confusion limited. Observational challenges: Foreground/ signal > 10 3 . RFI issues. Initial results via cross-correlation with optical surveys are promising (Chang+10, Masui+13, Switzer+13), but needs solid auto power spectrum measurements. Wednesday, June 5, 2013
21cm Intensity Mapping Cross-correlating GBT HI & WiggleZ optical galaxies at z ~ 0.6-1 200 hours, 41 deg 2 survey at the GBT 1 Measuring the WiggleZ fields 15 hr 1 hr at 800 MHz band, 0.5 < z < " HI b HI r = 0.43 10 -3 1.1 0.1 Foreground subtraction using ! (k) 2 (mK) SVD in freq-freq covariance matrices, and correcting for 0.01 frequency dependent beam Foreground subtraction down to factor of >100 0.001 0.1 HI brightness temperature k (h Mpc -1 ) on these scales at z=0.8: Masui+, GBT-HIM team, 2012 Ω HI r b = (4.3 ± 1.1) x 10 -4 Wednesday, June 5, 2013
Wednesday, June 5, 2013
Wednesday, June 5, 2013
21cm Intensity Mapping Current limits on 21cm auto power spectrum and measurements on Ω HI b HI at z=0.8 using the GBT. Ω HI b HI = [0.62 +0.23 -0.15 ]x 10 -3 Switzer+ 13, the GBT-HIM team Wednesday, June 5, 2013
Goal: Baryon Acoustic Oscillations courtesy of M. Blanton SDSS III BOSS Anderson+12 Wednesday, June 5, 2013
21cm Intensity Mapping current/future telescopes GBT-HIM multi- beam 2345)6!"#"" '%7&"(#$%3&","#".$%*8" !"#"$%&'(" ("#")*%'"+," CHIME/Tian-Lai/CRT/BAORadio BAOBAB 90 m 90 m 40 m 40 m FFT/OMNISCOPE Telescope SKA-low and SKA-mid Telescope BINGO Wednesday, June 5, 2013
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