21CMA

21 Centimeter Arraya.k.a. PAST

Reionization21cm: hyperfine transition of neutral Hydrogen

21CMA a.k.a. PASTBasic ideas:

• an experiment, not an observatory• use cheap, off-the -shelf technology (i.e. TV+PC)• simple design (looking at NCP)• choose site with minimal EM interference• to become operational before MWA/LOFAR

Xiang-Ping Wu (NAOC)Ue-Li Pen (CITA)Jeff Peterson (Carnegie)

VLBI

Map of 21CMA site

21CMA

E

N

Urumuqi

Ulastai

Log-Periodic antenna

20m

A pod (127 antenna)

correlator

array LNA filter amplifierOptical

transmitter Opt. fibreOptical receiver ADC

21CMA data collection system

Basic Design of 21CMRAAt z=9, 10 comoving Mpc ~ 0.6 MHz, ~ 3.6 arcmin

frequency range 70-200 MHz (6.1<z<19.3)

baseline: 2 km, (at 140 MHz, 3.6 arcmin)

Collecting Area 104 m2 A/L2 ~ 0.01

Schedule & Status• summer 2003 Ue-Li, Jeff, Xiang-Ping discussed the idea • autumn 2003 site search began, Ulastai chosen• March 2004 7-antennae prototype, first image• August 2004 array design finished• January 2005 batch I (first 20 pods) constructed• summer 2005 batch II (60 pods) construction, data collecting electronics installation • January 2006 fully operational

Total cost estimate: 15-30 M yuan, now borrowing from other groups in NAOC, will apply a grant, please support!

January 1, 2005

First skymap (dirty)

3C061.1

3CR390.3

NCP

3CR061.1

Dark Energy?• AP test• power spectrum measurement• lensing• ...

Discussion on dark energy observation

Dark Energy? Observation Data

Theoretical Assumptions

General Relativity Cosmo Principle

G 8∂GT (Ë )μ μ=

Model I Model II Model III

Ways to measure dark energy

Gravitational test:• luminosity distance• angular diameter distance• growth of perturbation• solar system & beyond

Non-Gravitational test:• variation of constants• dark energy interaction

• supernovae & GRB• gravitational lensing • cluster • large scale structure • CMB• 21cm• gravitational wave• micro-gravity, solar system & lab

What can we do in ChinaExisting projects: LAMOST, 21CMA

New Projects: ?