21CMA - Welcome to NAOC

Location?

West China: World’s best clear dark sky

VLBI

SNW1 pod=127 antennascontrol room21CMA Layout81 pods along two perpendicular arms (6km+4km)EBaselines: 3240 Freq channels: 4096Total data size: 4 terabytes / day

20mLog-PeriodicAntenna

The VHF Sky Brightness21CMA408MHz

signal signal signal signal signalopt. receivergainADC200M/sclockcomputer FFT correlationTopspin:InfinibandEfficiency:50%diskFuture: FPGA

Optical ReceiversData Acquisition SystemData processing systemUlastai Observatory

FM radioAviationcommu.LEO Satellites SatelliteBeaconsLEO Satellites

24h uvInstantaneous uvUV Coverage of 21CMA

SNWbaselines=3240 redundant baselines=212V u v GGV u vobs* trueij( , ) =i j ij( , )V u v G G V u vobs* trueαβ( , ) =α β αβ( , )T−1TG ⎡A A⎤A V obs= ⎣ ⎦A = [ 781×146]A = [ 820×147]N-SE-WEIonospheric Effect: Redundant calibration

Radio Sky Seen with 21CMA100 sqr deg around NCP region10 o 10 o

6Csources

point sourcesbackground

Sensitivity of 21CMABAO

21CMA: Measurement ErrorsFOVbaseline

Galactic synchrotronpoint sourcesGalactic free-freeextragalactic free-free21cmCMBThe 21cm power spectrum at z=9.2 (freq=140MHz) (Santos, Cooray & Knox 2005)

Iliev et al. (2005) Wang, Tegmark, Santos & Knox (2006)

T = T + T + T + T + Ttot 21cm syn ff ps noiseΔT( nˆ)T=∞∑l=0l∑m=−lalmYlm( nˆ)=f+21cm +noiselm lm lm lma ( ν ) a ( ν) a ( ν) a ( ν)Ctotlf 21cm N( ν1, ν2) = Cl( ν1, ν2) + Cl ( ν1, ν2) + Cl ( ν1, ν2)δ12

Byproducts @ 21CMA1. Ionosphere & the Milky Way2. QSOs at Low Frequencies3. Transient Sources (eg GRBs)4. Cosmic Ray Air Showers5. Meteors

Current Biggest Problems: Funds1. Operation and maintenance2. Data storage (4T/day) -$30k/month3. 10000 LNAs ($3M ) – (system noise)Operated for three months only so far !

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