cosmology using 21 cm emission jeff peterson, cmu talk 1…update on early ionization telescopes...
TRANSCRIPT
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Cosmology using 21 cm emission
Jeff Peterson, CMU
• Talk 1…Update on early ionization telescopes (LOFAR, PAST, GMRT)
• Talk 2…Proposed Redshift survey
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Telescopes with > 10,000 m^2 area that will be used in
attempt to detect early (z~10) ionization
•LOFAR
•PAST/21CMA
•GMRT
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Simulated VHF sky images
Furlanetto, et.al2003
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Extragalactic Foregrounds
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NETHERLANDS: LOFAR
• 120-240 MHz• ~10,000 dipoles• Blue Gene
correlator• Extensive
outrigger network• 53 M euros• Operational 2007
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TEST ARRAYS “ITS”
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CHINA:The Primeval StructureTelescope,aka 21 CM Array
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E
WS N
21CMA Layout
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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
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FFT
FFT MAC
MAC Infinband Network Switch
Data Storage
Phased Array
80
Analog Optical Fiber Link
8 Bit ADC
Pentium PC
PCI 64/66
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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
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Questions on Early Ionization
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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
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Baryon Wiggles Detected by SDSS and 2df
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Projected W and W’ sensitivity
Blake and Glazebrook
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Dark Energy Constraint vs. redshift limit
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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
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Four Cylinders each 2 km long
• Line feeds at foci used to create 4000 beams N
2 km
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Cylindrical reflectors use
suspended mesh, with a line of feed
points
Reflector Cost: ~$20/m^2
Survey Speed~A*N
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Existing cylinders
MOLONGLO
Cost:$12/m^2 (current dollars)
OOTY
Both rotate in one dimension
Molonglo
AUSTRALIABrisbane
Darwin
PerthCanberra
Hobart
AdelaideMelbourne
Sydney
+
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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
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Beam Former Signal Flow
FFT vs tTranspose
FFT vs t
4096 ADCs
…
FFT vs x
FFT vs x
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64 x 64 Processor Array
64
64
One of 4096 RF signals
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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
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Subaru Deep Field
z~6 Ly alpha