The Cylinder Radio Telescope: Observing the CMB Paul A. Fleiner Ph 70 Popular Presentation May 10, 2011

Outline Radio Astronomy 21cm Baryon Acoustic Oscillations (BAOs) Cylinder Telescope – Prototype – Possible Sites – Challenges Looking Ahead

Radio Astronomy: The Beginning Early Attempts – Nikola Tesla, Oliver Lodge – Attempted to observe radio emissions from the sun – Unsuccessful Technical Limits

Radio Astronomy First RA observations – Karl Jansky, 1930s – Bell Labs

Jansky’s Discovery Investigating source of interference in short-wave trans- Atlantic transmissions Initially thought source was solar – Happened every 23 hours, 56 minutes Actually Milky Way

Modern Radio Telescopes Very Large Array (VLA) – New Mexico, 1980 – $78.5m, ~$10,000/m 2 Square Kilometer Array (SKA) – Australia, 2024 – >$2b, $1,000/m 2 (Target)

How do they work?

What We “See” Hydrogen atom moving away from us is redshifted: – f=700MHz – λ=42cm Hydrogen atom at rest: – F=1420MHz – λ=21cm

Baryon Acoustic Oscillation (BAO) Method of tracking expansion of universe About 400,000 years after Big Bang – Universe expanded, temperature cooled – Electrons and protons combine to form H Photons no longer Thompson scattered Observing these photons gives us a “ruler” for measuring expansion

BAO Can use the ruler to plot the redshift – Can create a 3D mapping of the universe through time – Measure the expansion – Will help us quantify “dark energy”

Cylinder Radio Telescope Popular from Abandoned in favor of devices with cryogenically cooled pre-amps Illinois 400 ft Telescope, circa 1960

CRT Enabling Technology Low Noise Amplifiers (LNAs) are much cheaper T<<300K Increased capabilities of Analog to Digital Converters (ADCs) Better Digital Signal Processing GPUs, FPGAs More sophisticated FFTs (N log N) High speed, low power, low cost Reduces the cost to ~$100/m 2

CRT Design Parabolic half-cylinders Focuses radio waves radially inward – Strikes axial array of antennas Key Requirements – High Resolution Overall array size, time observed – Large Sky Coverage Number of channels – Large Redshift Range Bandwidth

CMU Prototype Built by Prof. Peterson’s group in Pittsburgh

Goal Design Array of 10 cylinders – 10m wide, 100m long Coverage – 20,000 sq. degrees Frequency Range – MHz Bandwidth – >200MHz

Challenges Synchrotron frequency, free-free emission – Total 21cm signal is ~300µK – 21cm BAO signal is only ~300nK Instrument Calibration Environment Calibration – RF Interference Far from power lines, most electronics

Possible Sites Several in Morocco

Moving Forward Model removal of foreground noise Build 2 to 3 cylinders – 10m wide, 50m long Set up larger prototypes in less noisy place Actually remove noise

Acknowledgements Professor Jeff Peterson, CMU Kevin Bandura, PhD Candidate Bruce Taylor, Communication and Facilities Consultant