Synergies between 21cm intensity mapping, optical, and CMB surveys. Alkistis Pourtsidou, ICG Portsmouth

Transcription

1 Synergies between 21cm intensity mapping, optical, and CMB surveys Alkistis Pourtsidou, ICG Portsmouth Fundamental Physics with the SKA, Mauritius, 1-5 May 2017

2 The HI intensity mapping (IM) method [Battye et al 2004, Chang et al 2008, Peterson et al 2009, Seo et al 2010, ] galaxies IM map Detecting HI galaxies is very expensive. But cosmological information is on large scales Get an HI intensity map of the 21cm emission line in a large pixel Similar to the CMB but 3D! [Image credit: Steve Cunnington] Signal of the order 0.1 mk - foregrounds much bigger 21cm IM surveys: GBT, BINGO, CHIME, HIRAX, MeerKLASS, SKA!

3 The case for IM-optical cross-correlations Foregrounds, noise, and systematics are a big challenge for IM GBT x WiggleZ showed that cross-correlating with optical can mitigate this! GBT HI b HI r =[0.43 ± 0.07(stat.) ± 0.04(sys.)] 10 3

4 HI constraints HI evolution is currently quite poorly constrained Important for astrophysics and cosmology alike! GBT [c.f. Crighton et al 2015]

5 MeerKLASS: An IM survey with MeerKAT Large improvement on current constraints using MeerKAT IM Other science: BAOs, RSDs, fnl [Santos et al, Fonseca et al, AP et al, ] Future: SKA1-Mid IM [Bull et al, Santos et al] MeerKAT: 64 dishes with 13.5 m diameter Use MeerKAT array in single-dish mode to perform an IM survey, 4000 sq. deg and 5 months observation time [PI: Mario Santos] [Bull, Camera, Maartens, AP, Witzemann, ] [AP et al 2016]

6 Radio-optical cross-correlations [MeerKLASS x DES-like] [AP et al 2016] Euclid z ( HI b HI )/( HI b HI ) Lband UHF band DES [SKA1-Mid x Euclid-like] [AP et al 2016] z (f 8 )/(f 8 ) D A /D A H/H UHF band [Also see Wolz 2016, 2017 et al for IM-optical cross-correlations science!]

7 Testing inflation with CMB and IM Tests of inflation via the scalar spectral index And its runnings ( s, s) n s Planck Planck 2015 Single-field inflation most popular bus also harder to test: predicts s Planck constraint: ( s )=0.007 Need an order of magnitude improvement! COrE is a Stage IV CMB mission, with a noise level much lower than Planck. It predicts: COrE mission! ( s )= Use the combined data from CMB and LSS to reach the required precision!

8 Testing inflation with CMB and IM Single-dish [SKA1-Mid IM] Interferometer [SKA2-Low IM] Need an interferometer array with small dishes that can probe high redshifts and has high sensitivity Consider an SKA2-Low-like array with: - 7,000 6m stations - closely packed together in an area with 700 m diameter - IM survey at 3<z<5 covering half the sky in 10,000 hrs

9 Testing inflation with CMB, optical, and IM surveys [AP 2016] Survey (n s ) ( s ) ( s ) Planck COrE-like COrE-like + SKA1-MID (sd) COrE-like + SKA2-MID-like (sd) COrE-like + HIRAX COrE-like + HIRAX (higher k NL ) COrE-like + SKA2-LOW-like (compact) COrE-like + Euclid-like [see also Munoz et al 2016] gives required precision < 0.001

10 Cosmology with SKA1-Low We propose an Intensity Mapping Survey with SKA1-Low at 3<z<6 Can get IM maps with SKA-Low at MHz Use them to constrain HI and cosmology [Chapman, AP, Pritchard, Wolz] SKA1-Low central : 524 stations with 1750 m max radius ***PRELIMINARY***