Steve Rawlings, Oxford, ESKAC and PrepSKA Cambridge, Dec 2010 SKA 1 Science Requirements The HI Universe from the Dark Ages to Present Day Pulsars for Fundamental Physics

Steve Rawlings, Oxford, ESKAC and PrepSKA Cambridge, Dec 2010 Science Driver for SKA MHz AAs: hi-z HI HI Science (Wilkinson 1991 to Garrett et al. 2010) Limits on the EoR monopole; Bowman & Rogers (2008) Limits on EoR at z~8.5 from GMRT; Paciga et al (2010) Direct HI detections to z~0.2 with WSRT (f~0.01); Verheijen et al (2010) Delhaize & Staveley-Smith (2010) Chang et al (2010)

Steve Rawlings, Oxford, ESKAC and PrepSKA Cambridge, Dec 2010 SKA 1 AA leads naturally to SKA 2 AA Compared to ~arcmin 2 FOV of ALMA SKA 1 ~100s deg 2 FOV up to ~0.5 GHz Detection and mapping of the EoR SKA 2 ~100s deg 2 FOV up to ~1.0 GHz Billion Galaxy Redshift Survey to z~2 and fundamental cosmology: outstrips WFIRST/Euclid

Steve Rawlings, Oxford, ESKAC and PrepSKA Cambridge, Dec 2010 Why SKA 1 must have AAs with A/T sys ~2000 m 2 K -1 At z=8.5, T sys ~T sky ~500K Solid curves are for SKA 1 with A/T sys =2000 m 2 K -1 Assumes a ‘fully-filled’ core: D= 1 km has a 7’ ‘beam’ This means we reach S/N>1 regime in reasonable times If SKA 0 does detect EoR, SKA 1AA will be needed to map fluctuations (c.f. CMB) If SKA 0 does not directly detect EoR: RFI, ionosphere, polarized foregrounds issues become much more tractable in the S/N>1 regime Simulations (Furlanetto et al. 2004) ignores HII regions and z- space distortions, ~agrees with state-of-the-art; e.g. Jelic et al. (2008)  = 0.5 MHz

Steve Rawlings, Oxford, ESKAC and PrepSKA Cambridge, Dec 2010 What will precursors and pathfinders tell us? LOFAR core and MWA512 both have filling factors ~1% in the central 1 km In even long (1000 hr) exposures they will be working in the S/N<<1 regime Foregrounds are 10 4 times brighter and strongly polarized Ionospheric corrections and RFI excision are challenging (c.f. GMRT) Based on the difficulty of measuring the auto-correlation signal of HI at z~1 with GBT, with more benign issues, direct EoR detection would be a fantastic achievement X-correlation can help enormously

Steve Rawlings, Oxford, ESKAC and PrepSKA Cambridge, Dec 2010 Why r = 100 km I: Ly  Emitters in the EoR VISTA simulations (5% escape fraction; Heywood et al), VISTA data (Jarvis et al) In SKA 0 (e,g. MWA512 and LOFAR) EoR fields (~ deg 2 ), there will be samples for stacking and X-correlation at z~7 (see Jarvis talk) We will ONLY be able to isolate HI in galaxies if it can be isolated by RESOLUTION Things will be harder at higher redshifts (earlier epochs), both in finding Ly  tracers, and because correlation might be positive or negative! (resolution will be key) ~20hr exposures with VISTA Data just taken, candidates identified  Spectroscopic confirmation underway

Steve Rawlings, Oxford, ESKAC and PrepSKA Cambridge, Dec 2010 Why 2 = 450 MHz? z~2 HI. MeerKAT results in ~2014, and first results from SKA 1 in ~2018, needs objects to ‘stack’ on: equatorial HETDEX will have ~million of these! SKA 1 + HETDEX cross-correlation uniquely powerful probe of z~2 power spectrum Options for extending to ‘all sky’ with ~10 9 galaxies: SKA 2 or Euclid/WFIRST

Steve Rawlings, Oxford, ESKAC and PrepSKA Cambridge, Dec 2010 IFU 448 fibers 50 x 50 sq. arcsec 1.5” fiber dia HETDEX with VIRUS on HET Net fill factor in survey is 1/7 (60 sq. deg in 420) Spring field approx 10 x scale Slide from Gary Hill (Texas) Blind survey with 150+ VIRUS –33,600 spectra per exposure –350 – 550 nm –Survey begins 2012 –0.8 million LAEs in 9 Gpc 3 volume 1.9 < z < 3.5 –>1 million [OII] emitters z < 0.48 –First detection of dark energy at z>2 Fall field equatorial

Steve Rawlings, Oxford, ESKAC and PrepSKA Cambridge, Dec 2010 New Technique: “Intensity Mapping” Chang et al (2010) ~10,000 optical galaxies from DEEP2 over ~1 deg 2 : ‘drift scan’ with the GBT Good RFI conditions essential z=0.53 to z= 1.12 driven by frequency range of GBT (f=0.01): much longer in z than on sky 15’ (13 Mpc) beam so sums emission on large scales:  >> expected for effective exposure time ~0.5 hr in each of ~8 ‘pointings’ Intensity Map (autocorrelation) is upper limit to HI signal ‘X-correlation’ (stacking) reduces systematic error, and provides ~SKA sensitivity Detection at z~0.8 exactly as predicted by SKADS simulations (great news for SKA!), but suggests X-correlation is essential in the S/N<1 regime: and still misses HI not clustered with tracers  ~4 mK ~4  detection at 0.15 mK

Steve Rawlings, Oxford, ESKAC and PrepSKA Cambridge, Dec 2010 Below 151 MHz (z=8.5 HI) T sky ~500 ( / 151) -2.7 K Since signals remain at the mK level, progress into the dark ages probably requires much larger (SKA 2 ) collecting area, and may require even longer integrations But Ly  coupling from first stars produce strong fluctuations ~10 km 2 would give A/Tsys ~ ~250 New semi-numerical simulations extend to z~25 over ~1 Gpc 3 P(k) at z~20! Signatures of First stars! Santos et al (2010) z~20 Ly  coupling X-ray heating Why 1 = 70 MHz? Santos et al (2010)

Steve Rawlings, Oxford, ESKAC and PrepSKA Cambridge, Dec 2010 Beyond Einstein: from GR to Quantum Gravity Detect Gravitational Waves Study supranuclear matter Why dishes? Out of the Galactic Plane, surveys yield may benefit from SKA 1 AAs but only if they reach ~450 MHz (Smits et al. 2010). Needs GHz in Plane to combat interstellar scattering. Timing demands this GHz band. Must have a southern facility with A/T sys ~1000 m 2 K -1, e.g. 3xeVLA or MeerKAT, comparable to Arecibo or FAST in the north.

Steve Rawlings, Oxford, ESKAC and PrepSKA Cambridge, Dec 2010 CO Emitters in the EoR and SKA Simulations by Ian Heywood: and real eVLA data at z~6 (Carilli) looks very similar SKA 0 (MeerKAT) potentially - dependent on dish efficiency at ~15 GHz: z~7 CO(1-0) - world-beating: ~5-times faster than the VLA (largely) due to smaller dishes Heywood et al awarded 6000 MeerKAT hours for this experiment Stacking experiments fine, but to cover ~ deg 2 (MWA512/LOFAR) EoR patches, and get ~10-100k tracers (at z~8.5) would require new instruments (e.g SKA 1 dishes with ~10-times MeerKAT mapping speed), and to isolate contribution due to variance in galaxies still needs SKA 1 RESOLUTION Red: 5 

Steve Rawlings, Oxford, ESKAC and PrepSKA Cambridge, Dec 2010 Concluding Remarks In SKA 0-2 we are fortunate to have an iconic project with the credibility to ask for €0.35B soon, and an additional €1.2B by ~2020: this phasing helps SKA stay global given different international funding situations but success requires global coherence to give confidence to funders, and to optimally solve the remaining challenges SKA 0 (e.g. MWA512 or LOFAR) could detect EoR fluctuations, but will most likely need to use X-correlation techniques to do so: Ly  and CO tracers both look promising Direct detection of the EOR (via auto-correlation) may need the S/N>1 regime, and hence strongly motivates an SKA 1 with A/T sys ~2000 m 2 K -1, and a high-filling-factor core (irrespective of SKA 0 results) r=100 km, giving ~arcsec resolution for SKA 1 AAs, is needed to isolate HI variance due to galaxies from HI in IGM Up to 450 MHz AA capability with SKA 1 can measure P(k) at z~2 leading to transformational cosmology with SKA 2 with mid-frequency AAs Down to ~70 MHz capability can probe the z~20 dark ages (first stars)! Dishes needed for pulsar key science driver, and may significantly aid EoR studies