Oxford Astrophysics C-BASS – The C-Band All Sky Survey Oxford University – Oliver King, Christian Holler, Mike Jones, Angela Taylor, Matthew Brock, Jaya John John, Paul Grimes –Secondary Optics, Feed, Polarimeter/Receiver, Cryogenics, Backend Manchester University – Rod Davies, Richard Davis Clive Dickinson, Tess Jaffe, Paddy Leahy, Stuart Lowe, Neil Roddis, Althea Wilkinson, Peter Wilkinson –Low Noise Amplifiers CalTech/JPL/OVRO – Dayton Jones, Russ Keeney, Charles Lawrence, Erik Leitch, Stephen Muchovej, Tim Pearson, Tony Readhead, Graça Rocha, Matthew Stevenson –Northern Survey, OVRO Antenna, Backend and Data Acquisition Rhodes University/HartRAO – Roy Booth, Charles Copley, Justin Jonas –Southern Survey, MeerKAT Support Site Antenna

Oxford Astrophysics C-BASS – The C-Band All Sky Survey GHz all sky survey of intensity and polarization 0.85° FWHM maps to 100 µK rms noise per pixel (I, Q and U) Systematics below 5% of noise Science goals: – Survey of diffuse galactic synchrotron emission – Provide synchrotron foreground template for CMB missions – Study galactic magnetic field and interstellar medium Instrument: – Combined correlation radiometer and pseudo-correlation polarimeter with e-Merlin LNAs –Actively controlled 4 K reference loads – Profiled corrugated horn and planar OMT – 6.1m dish at OVRO and 7.1m dish at MeerKAT support site – each with new shaped 2 ndry and absorber tunnel – First receiver – analogue backend for South African site – Second receiver – all-digital backend for OVRO (for RFI excision) – Dedicated RFI monitor at OVRO

Oxford Astrophysics Receiver and optics

Oxford Astrophysics Status and Timescales Both antennas on-site and undergoing commissioning 1 st receiver, secondary and foam support to be shipped to OVRO Weds/Thurs – Receiver tested on sky in Oxford – T sys < 20K, stability good – Will be tested at OVRO with initial survey before shipping to MeerKAT site 2 nd (digital backend) receiver construction to start soon – Planned ship date to OVRO – Feb 2010 OVRO commissioning Jul-Sept 2009 Initial Northern survey/testing - Sept 2009-Jan 2010 Southern survey - 1 year from Mar 2010 Northern survey – 1 year from Sept 2009 Data release 2011/12

Oxford Astrophysics Predictions I, Q and U maps – Planck sky model Compare Planck to Planck + C-BASS (Single pixel, MCMC parameter fits) Typical high latitude pixel (2° beam): –Spectral index bias reduced – Stokes I to 0.015; Q,U to 0.03 –70 GHz synchrotron amplitude error – Stokes I 0.09 μK to 0.03 μK; Q,U 0.3 μK to μK –70 GHz synchrotron bias – Stokes I 0.9 μK to 0.15 μK; Q,U μK to μK 5-7 times reduction in synchrotron residuals in CMB band