Measuring extragalactic Faraday rotation

Transcription

1 Measuring extragalactic Faraday rotation N. Oppermann*, H. Junklewitz*, M. Greiner*, T.A. Enßlin*, T. Akahori, E. Carretti, B.M. Gaensler, A. Goobar, L. Harvey-Smith, M. Johnston-Hollitt, L. Pratley, D.H.F.M. Schnitzeler, J.M. Stil, V. Vacca* *MPI für Astrophysik

2 Galactic Faraday rotation

3 Faraday rotation Angular Power Spectrum pr ev th iou is sw wo or rk k

4 Numerical Information Field Theory Information Field Theory Selig et al. (arxiv: ) Code &

5 Theory Applications... D3PO Selig et al. (2013) arxiv: is a versatile PYTHON library incorporating CYTHON, C++, and C libraries operates regardless of the underlying spatial grid and its resolution The Y wayway signal inference TheNIFT signal inference by Marco S 5

6 Theory Applications D3PO Grid independence The Y wayway signal inference TheNIFT signal inference by Marco S 6

7 Theory Applications D3PO Grid independence 1D 2D x128 2D 32x32 The Y wayway signal inference TheNIFT signal inference by Marco S 7

8 Theory Applications D3PO Grid independence 1D 2D x128 2D 32x32 The Y wayway signal inference TheNIFT signal inference by Marco S 8

9 Theory Applications... D3PO Selig et al. (2013) arxiv: is a versatile PYTHON library incorporating CYTHON, C++, and C libraries operates regardless of the underlying spatial grid and its resolution abstracts spaces, fields, and operators into an object-orientated framework The Y wayway signal inference TheNIFT signal inference by Marco S 9

10 Theory Applications classes object space field operator parameters domain space domain space field values target space D3PO Selig et al. (2013) arxiv: instance methods applying to fields The Y wayway signal inference TheNIFT signal inference by Marco S 10

11 Theory Applications classes object space operator field point_space rg_space lm_space hp_space gl_space nested_space D3PO Selig et al. (2013) arxiv: unstructured list of points n-dimensional regular grid spherical harmonics Gauss-Legendre grid HEALPIX grid (arbitrary product of grids) The Y wayway signal inference TheNIFT signal inference by Marco S 11

12 Theory Applications classes object space operator field point_space rg_space lm_space hp_space gl_space nested_space D3PO Selig et al. (2013) arxiv: probing diagonal_operator power_operator projection_operator vecvec_operator response_operator invertible_operator propagator_operator explicit_operator The Y wayway signal inference TheNIFT signal inference by Marco S 12

13 Spectral smoothness prior Oppermann et al. (2012) unknown signal correlations inverse-gamma prior The Y wayway signal inference TheNIFT signal inference by Marco S 13

14 Spectral smoothness prior Oppermann et al. (2012) unknown signal correlations inverse-gamma prior and spectral smoothness prior σ2 = 1000 σ2 = The Y wayway signal inference TheNIFT signal inference by Marco S 14

15 Galactic Faraday rotation

16 Data filtering

17 Data filtering

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20 Faraday rotation dispersion

21 AreAllyou a VIP or a SIP? data are equal! VIP = Very Informative Point, SIP = Somewhat Informative Point

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24 VIP = Very Informative Point, SIP = Somewhat Informative Point

25 Posterior samples

26 Correlation structure in posterior samples

27 Information gain on

28 Summary New method to measure extragalactic Faraday rotation statistically. Verified with simulated data. Gives an extragalactic Faraday dispersion of 6.4 rad/m² for most reasonable data split in VIP and SIP categories. Method provides a posteriori samples of individual extragalactic RMs for further studies. Although this posterior sample was drawn under a specific prior (extragalactic RM variance is uniform), simple re-weighting enables their usage under other priors as well.