Gaitskell CMB Polarization DASI Recent Results Brown Astro Journal Club Rick Gaitskell (Brown University)
Brown APJC Oct 2002 Rick Gaitskell Andy Warhol - Pop Artist 1960’s - “Exactly” The pop artist Andy Warhol once approached me at a party and told me that he collected scientific journals, but he couldn't understand them. He drifted away, then came back and said, "Do you mind if I ask you a question?…Why does science take so long?" I said, "Mr. Warhol, when you do a picture of Marilyn Monroe, does it have to be exactly like her, as close to being her as you can make it?" He said, "Oh no." I said, "Well, in science it has to be exact, as EXACT as you can make it." He looked at me with sympathy and said, "Isn't that terrible?" Gerald M. Edelman Bright Air, Brilliant Fire (1992)
Brown APJC Oct 2002 Rick Gaitskell DASI
Brown APJC Oct 2002 Rick Gaitskell References - used for talk DASI Exp Results: Leitch et al. astro-ph/ DASI Instrumentation Paper Kovac et al. astrop-ph/ Animations of CMB l-power spectra: Angelica de Oliveira-Costa Dependence on various cosmological parameters Pictures and some of slides taken from (COSMO-02 Conference: John Kovac) DASI Experimenta Site “Polarization Primer”: Hu and White Harvard - Journal Archive Rees’s original 1968 paper (ApJ 153 L1)
Brown APJC Oct 2002 Rick Gaitskell Why is Polarization Important? (Old) CMB polarization is induced via Thomson scattering, which occurs either at decoupling or during a later epoch of reionization. The level of polarization is linked to the local quadrupole anisotropy of the incident radiation on the scattering eletrons, and it is expected to be 1-10% of the amplitude of the temperature anisotropies depending on the angular scale. CMB polarization is important for two reasons: first, polarization measurements can substantially improve the accuracy with which parameters are measured by breaking the degeneracy between certain parameter combinations; second, it also offers an independent test of the basic assumptions that underly the standard cosmological model. Contrary to most of the Astronomy field that uses the Stokes parameters Q and U to describe their polarization measurements, in the CMB field we make use of two scalar fields E and B that are independent of how the coordinate system is oriented, and are related to the tensor field (Q,U) by a non-local transformation. Scalar CMB fluctuations have been shown to generate only E-fluctuations, whereas gravity waves, CMB lensing and foregrounds generate both E and B.
Brown APJC Oct 2002 Rick Gaitskell Why is Polarization Important? CMB polarization is induced via Thomson scattering Occurs either at decoupling (or during a later epoch of reionization). The level of polarization is linked to the local quadrupole anisotropy of the incident radiation on the scattering eletrons, Expected to be 1-10% of the amplitude of the temperature anisotropies depending on the angular scale. CMB polarization is important for two reasons: Can substantially improve the accuracy with which parameters are measured by breaking the degeneracy between certain parameter combinations Offers an independent test of the basic assumptions that underlie the standard cosmological model. CMB field we make use of two scalar fields E and B that are independent of how the coordinate system is oriented, Are related to the tensor field (Q,U) [Stokes parameters] by a non-local transformation. Scalar CMB fluctuations have been shown to generate only E- fluctuations, whereas gravity waves, CMB lensing and foregrounds generate both E and B.
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell DASI (2) 13-element interferometer measure temperature and polarization anisotropy of CMB l multipole range ~ 140–900 Horn separations cm HEMT amplifiers running between 26-36GHz, in ten 1 GHz channels Operates from the NSF Amundsen-Scott South Pole station Recent Results Data: Two 3.4 degree FWHM fields (separated by 1 hour RA) run in 2001 and 2002, Selected from 2000 scans — Wish to avoid point sources — High galactic lattitude
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell Astro-ph/
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell
Brown APJC Oct 2002 Rick Gaitskell Curvature
Brown APJC Oct 2002 Rick Gaitskell Baryon
Brown APJC Oct 2002 Rick Gaitskell Tensor
Brown APJC Oct 2002 Rick Gaitskell Questions Arising How is quadrapole generated by velocity flows, and how does it actually lead to E-polarization Try Rees, M J 1968 ApJ 153 L1 How does one interpret visual examples of E-field and B- field, especially wrt to Curl = 0, and Curl ≠ 0 Check how Sum and Difference cross-checks are performed