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The conquest of sky polarization. N. Ponthieu (IAS). The upper limits era First detections Prospects Foregrounds. The very beginning…. free from seasonal variations (July, 1964-April, 1965). D. Barkats. Penzias & Wilson, (1965), ApJL, 142, 419. The very beginning….
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The conquest of sky polarization N. Ponthieu (IAS) • The upper limits era • First detections • Prospects • Foregrounds
The very beginning… free from seasonal variations (July, 1964-April, 1965). D. Barkats Penzias & Wilson, (1965), ApJL, 142, 419
The very beginning… Rees, (1968), ApJL, 153, L1 Already discusses the impact of reionization on the detection of polarization
The targets… Propagating electromagnetic wave Stokes Parameters Bolometers, total power measurements ( ≥ 30GHz) HEMTS, Interferometers, correlators ( ≤ 150GHz)
The targets… • I, Q, U: XIXth century • E,B : Seljak & Zaldarriaga, 1997
The upper limits era: 1965-2002 More than 4 orders of magnitude in sensitivity gained in 37 years until the first detection by DASI (Kovac et al, 2002) De Oliveira-Costa et al, 2002 Caderni 1978: balloon Lubin, Smoot, Nanos: ground
The upper limits era: 1965-2002 More than 4 orders of magnitude in sensitivity gained in 37 years until the first detection by DASI (Kovac et al, 2002) Courtesy D. Barkats De Oliveira-Costa et al, 2002 Caderni 1978: balloon Lubin, Smoot, Nanos: ground
The first measurements… See F. Piacenti’s talk See B. Mason’s talk NEW RESULTS FROM CBI AND BOOMERANG TODAY!
Temperature/Polarization cross power spectrum See F. Piacenti’s talk See B. Mason’s talk NEW RESULTS FROM CBI AND BOOMERANG TODAY!
… and fortunately, lots of people think so too Ground Balloon Satellite 2005 2006 2007 2008 2009 2010 2015-2020 WMAP Maxipol QUAD BICEP Clover Brain CMBpol Satellite EBEX Planck Spider PolarBear QUIET See B. Jones’ talk See K. Ganga’s talk See D. Barkats’ talk + PAPPA (Sorry i couldn’t find when) Numbers of detectors increase, move towards matrices Mainly Bolometer experiments…
Projected sensitivities EE BICEP
Projected sensitivities EE Clover SPIDER Unofficial, NP’s plot
Projected sensitivities BB BICEP Unofficial, NP’s plot
Projected sensitivities BB Clover Brain T/S = 0.7 T/S = 0.1 T/S = 0.01 T/S = 0.001
OK OK ? ~2012 Taking t = first light + 2 yrs data analysis, we should be on time with the WL and move on to primordial B !
B mode dedicated satellite around 2020 ? • Resolution is not a true issue • Sensitivity is critical: thousands of detectors which may lead to “large” focal planes at short wavelengths, new electronics, cryogenics… • Control of systematics is critical • Ultimately full sky observation • Atmosphere makes large angular scales difficult to deal with • Foregrounds, the ultimate limit ? • The 2 bumps signature of B… A satellite seems to be the only possibility to reach the limits, but there is much science to do and much to learn from earth based experiments until then Ongoing studies in the US (Beyond Einstein Probes) and in France at least
The foregrounds issue Tucci et al, astro-ph/0411567
The foregrounds issue B Grain Optical polarization submm polarization • The acceleration of electrons in the magnetic galactic field polarizes the synchrotron radiation • Dust thermal radiation is polarized provided that the grains are asymetrical and aligned See P. Martin’s talk Serkowski et al 75 Heiles 01 Fosalba et al 02 Lack of data on large angular scales to characterize this field
First detection of Dust polarization thermal radiation on large angular scales by Archeops (flight 2002) Benoit et al, 2004, AA, 424, 571 • 5% polarization in the Galactic plane • Some clouds show 10% • Due to confusion along the line of sight in the plane, we may expect at least as much polarization at high latitude • 353GHz • Fsky ~ 20% of the sky • 13 arcmin resolution (smoothed here for the display)
First estimation of the angular power spectra of dust thermal polarization on large angular scales See M. Tristram’s talk • |b| ≥ 5 : 4 detection on 3 < l < 8 • |b| ≥ 10: 2 detection on 3 < l < 8 • Decreasing amplitude with increasing latitude cut consistent with astrophysical origin of the signal Ponthieu et al, 2005, AA, in press
Contamination to CMB anisotropy measurements |b| ≥ 5, 100GHz: Toy model: • Constant index: 1.7 • Equal weight 23, 33, 41, 61, 94GHz • Archeops + Kp2 • Need an extrapolation to lower "CMB frequencies" • Generalization to the whole sky is uncertain • Archeops results obtained @353GHz • ~ 20% of the sky Lagache 2003, Finkbeiner 2004 [90, 353] GHz: I(dust) ~ 1.7B(T) Next data? : BLAST, PILOT See P. Martin’s talk See JP Bernard’s talk Ponthieu et al, 2005, AA, in press
Contamination to CMB anisotropy measurements Archeops (b>5deg) Residual dust if constant index Residual dust if white noise uncertainty on the spectral index See F. Stivoli’s talk Minimal assumptions on the component separation show encouraging results but lots of uncertainties remain See J. Aumont’s talk Tucci et al, 0411567
Conclusions • Significant contributions have come from the ground, balloons and satellites • Lots of ongoing experiments are dedicating themselves to polarization and projected sensitivities are very promising • ISM physics and cosmology benefit from eachother and will go on this way
Instruments: • Need sensitivities higher by an order of magnitude (at least) • Need developpements on detector arrays, electronics read outs, cryogenics • Need proportionnally higher control of systematics • Focus on high frequencies (sensitivity + instruments design) ? Sky observations: • Need more data to improve our understanding of the ISM: spectral indices ? Variations of spectral indices ? Variation of alignment ? Variation of polarization degree with wavelength ? … • Great sensitivities projections for ongoing and near future experiments, but still not clear how will the foregrounds interfere with these. Perspectives
