Cosmology using 21 cm emission

Jeff Peterson, CMU

• Talk 1…Update on early ionization telescopes (LOFAR, PAST, GMRT)

• Talk 2…Proposed Redshift survey

Telescopes with > 10,000 m^2 area that will be used in

attempt to detect early (z~10) ionization

•LOFAR

•PAST/21CMA

•GMRT

Simulated VHF sky images

Furlanetto, et.al2003

Extragalactic Foregrounds

NETHERLANDS: LOFAR

• 120-240 MHz• ~10,000 dipoles• Blue Gene

correlator• Extensive

outrigger network• 53 M euros• Operational 2007

TEST ARRAYS “ITS”

CHINA:The Primeval StructureTelescope,aka 21 CM Array

E

WS N

21CMA Layout

Telescope Parameters

• Rough Parameters

• Total antennae 10,000• Interferometer Elem. 81• Effective area 20,000 m^2• Sky temperature 200 K – 2000

K• Imaging field of view 100 sq deg• Angular resolution 5 arc minutes• Frequency Range 70 - 200 MHz• Redshift range 6 - 20• Frequency resolution 20 kHz• Spatial resolution 6 Mpc• Mapping sensitivity 25

mK/sqrt(day)• Budget $3M• Operational 2006

280 antennae, on site, Ulastai June 2004

Over 2000 Installed, December 2004

FFT

FFT MAC

MAC Infinband Network Switch

Data Storage

Phased Array

80

Analog Optical Fiber Link

8 Bit ADC

Pentium PC

PCI 64/66

INDIA: The Giant Metrewave Radio Telescope

•30 44 m dishes•Currently hobbled by power line noise•New PC based correlator summer 2006•Budget $200,000 plus exisitng GMRT

Questions on Early Ionization

21 cm redshift survey to constrain dark energy

• By Jeff Peterson and Ue-Li Pen• Use acoustic oscillations from z = 0 to z = 1.5 to

detail the transition from deceleration to acceleration.

• Survey 2 Pi steradians from 500 to 1500 MHZ with a 250,000 sq m fixed-pointed meridian-scan radio telescope.

• Cylindrical reflectors allow for ultra-wide field observations, and inexpensive FFT based beam forming.

• Modest cost--$20M--$0.02/redshift

Baryon Wiggles Detected by SDSS and 2df

Projected W and W’ sensitivity

Blake and Glazebrook

Dark Energy Constraint vs. redshift limit

Local HI Luminosity Function

Zwann et al

at z=1.5 this is 2 microjanskyWe detect all these across 1/2 of sky in 6 months

Four Cylinders each 2 km long

• Line feeds at foci used to create 4000 beams N

2 km

Cylindrical reflectors use

suspended mesh, with a line of feed

points

Reflector Cost: ~$20/m^2

Survey Speed~A*N

Existing cylinders

MOLONGLO

Cost:$12/m^2 (current dollars)

OOTY

Both rotate in one dimension

Molonglo

AUSTRALIABrisbane

Darwin

PerthCanberra

Hobart

AdelaideMelbourne

Sydney

+

Cylinder History

• Popular 1960-1980• Lost favor with advent of cryogenically cooled pre-amplifiers.• Room temp amplifiers with 20K noise temp now available.

Illinois 400 ftTelescope ca. 1960

Beam Former Signal Flow

FFT vs tTranspose

FFT vs t

4096 ADCs

…

FFT vs x

FFT vs x

64 x 64 Processor Array

64

64

One of 4096 RF signals

Conclusions

• Using off the shelf technology, a redshift survey telescope can be built for modest cost ($20M) which will yield 10^9 redshifts to z~1.5

• Will cover 100 times the SDSS volume

• Will constrain W1 to ~0.1

Subaru Deep Field

z~6 Ly alpha