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Diffuse model fitting A. Strong, Dec. 2001

Diffuse model fitting A. Strong, Dec. 2001 Fitting SPI data to spatial models e.g. 1809 keV to CO, free-free, FIR, etc 511 keV to sum of Gaussians continuum to HI+CO+inverse Compton+sources Good method to produce spectra of diffuse emission

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Diffuse model fitting A. Strong, Dec. 2001

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  1. Diffuse model fitting A. Strong, Dec. 2001 Fitting SPI data to spatial models e.g. 1809 keV to CO, free-free, FIR, etc 511 keV to sum of Gaussians continuum to HI+CO+inverse Compton+sources Good method to produce spectra of diffuse emission Alternative to imaging (e.g. spiskymax) Many s/w components in common with other imaging s/w (data, response)

  2. Bayesian method: advantages: straightforward treatment of multiparameter problems adopted for many current astrophysical analyses large current literature, growing expertise at nearby CIPS institute spidiffit: input: SPI data SPI response (IRF) model skymaps (multichannel, from gensky) output fit parameters, error bars, distributions corresponding skymaps with error-bar skymaps (-> spectra of any sky region) method: MCMC (Monte-Carlo Markov Chain)

  3. spidiffit version 1 error analysis for multiparameter problems errors on arbitrary combinations of parameters can be obtained for arbitrary linear combination, covariance matrix sufficient (e.g. error on total of components for a fitted skymap -> spectra with errors) MCMC: Metropolis-Hastings method implemented see ADD for mathematical details

  4. spidiffit: ADD and first version written Tested on simulated GCDE surveys, works well 20 parameters: 1 model scaling, 19 detector background model scaling is parameter of interest: posterior marginalized over backgrounds

  5. 1809 keV 2.4 FWHM 240mm model scaled to COMPTEL maps spidiffit, singles only GCDE 1 year GCDE 5 years gcde.20 gcde.19

  6. 1809 keV 2.4 FWHM 240mm model scaled to COMPTEL maps spidiffit, singles only GCDE 1 year GCDE 1 years gcde.20 gcde.19

  7. GCDE 1809 keV 2.4 keV FWHM 240mm model spidiffit parameter posterior distribution of scaling factor marginalized over background 5 years 1 year 1808-1810 keV 1808-1810 keV 1810-1812 1810-1812 1812-1814 1812-1814

  8. Commissioning phase = 0.9 Ms staring+3*0.27 Ms 5X5 +0.2 hex Ms 1809 keV 2.4 keV FWHM 240mm model spidiffit Pointings Cygnus.3

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