# CMB spectrum and likelihood code

## Contents

## CMB spectra[edit]

### General description[edit]

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The Planck best-fit CMB temperature power spectrum, shown in figure below, covers the wide range of multipoles = 2-2508. Over the multipole range = 2–29, the power spectrum is derived from a component-separation algorithm, *Commander*: applied to maps in the frequency range 30–353 GHz over 91% of the sky Planck-2013-XII^{[1]} . The asymmetric error bars associated to this spectrum are the 68% confidence limits and include the uncertainties due to foreground subtraction. For multipoles equal or greater than , instead, the spectrum is derived from the *Plik* likelihood Planck-2015-A11^{[2]} by optimally combining the spectra in the frequency range 100-217 GHz, and correcting them for unresolved foregrounds. Associated 1-sigma errors include beam uncertainties. Both *Commander* and *Plik* are described in more details in the sections below.

### Production process[edit]

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The < 50 part of the Planck power spectrum is derived from the Commander approach, which implements Bayesian component separation in pixel space, fitting a parametric model to the data by sampling the posterior distribution for the model parameters Planck-2013-XII^{[1]}. The power spectrum at any multipole is given as the maximum probability point for the posterior distribution, marginalized over the other multipoles, and the error bars are 68% confidence level Planck-2013-XV^{[4]}.
The > 30 part of the CMB temperature power spectrum has been derived by the Plik likelihood, a code that implements a pseudo-Cl based technique, extensively described in Sec. 2 and the Appendix of Planck-2013-XV^{[4]}. Frequency spectra are computed as cross-spectra between half-mission maps. Mask and multipole range choices for each frequency spectrum are summarized in Section 3.3 of Planck-2015-A13^{[3]} and in Planck-2015-A11^{[2]}. The final power spectrum is an optimal combination of the 100, 143, 143x217 and 217 GHz spectra, corrected for the best-fit unresolved foregrounds and inter-frequency calibration factors, as derived from the full likelihood analysis (cf Planck+TT+lowP in Table 3 of Planck-2015-A13^{[3]}). A thorough description of the models of unresolved foregrounds is given in Planck-2015-A11^{[2]}. The spectrum covariance matrix accounts for cosmic variance and noise contributions, together with beam uncertainties. The > 30 CMB TT spectrum and associated covariance matrix are available in two formats:

- Unbinned, with 2479 bandpowers ( ).
- Binned, in bins of , with 83 bandpowers in total. We bin the power spectrum with a weight proportional to , so that the binned bandpower centered in is: Equivalently, using the matrix formalism, we can construct the binning matrix B as: where B is a matrix, with the number of bins and the number of unbinned multipoles. Thus: Here, is the vector containing all the binned (unbinned) bandpowers, is the covariance matrix and is the weighted multipole average in each bin. The binned power spectrum is then calculated as: .

### Inputs[edit]

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- Low-l spectrum ( )

- frequency maps from 30–353 GHz
- common mask Planck-2013-XII
^{[1]} - compact sources catalog

- High-l spectrum ( )

- 100, 143, 143x217 and 217 GHz spectra and their covariance matrix (Sec. 3.3 Planck-2015-A13
^{[3]}) - best-fit foreground templates and inter-frequency calibration factors (Table 3 of Planck-2015-A13
^{[3]}) - Beam transfer function uncertainties Planck-2015-A07
^{[5]}

### File names and Meta data[edit]

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The CMB spectrum and its covariance matrix are distributed in a single FITS file named

which contains 5 extensions

- LOW-ELL (BINTABLE)
- with the low ell part of the spectrum, not binned, and for l=2-49. The table columns are

*ELL*(integer): multipole number*D_ELL*(float): $D_l$ as described below*ERRUP*(float): the upward uncertainty*ERRDOWN*(float): the downward uncertainty

- HIGH-ELL (BINTABLE)
- with the high-ell part of the spectrum, binned into 83 bins covering in bins of width (with the exception of the last bin that is smaller). The table columns are as follows:

*ELL*(integer): mean multipole number of bin*L_MIN*(integer): lowest multipole of bin*L_MAX*(integer): highest multipole of bin*D_ELL*(float): $D_l$ as described below*ERR*(float): the uncertainty

- COV-MAT (IMAGE)
- with the covariance matrix of the high-ell part of the spectrum in a 83x83 pixel image, i.e., covering the same bins as the
*HIGH-ELL*table.

- HIGH-ELL (BINTABLE)
- with the high-ell part of the spectrum, unbinned, in 2979 bins covering . The table columns are as follows:

*ELL*(integer): multipole*D_ELL*(float): $D_l$ as described below*ERR*(float): the uncertainty

- COV-MAT (IMAGE)
- with the covariance matrix of the high-ell part of the spectrum in a 2979x2979 pixel image, i.e., covering the same bins as the
*HIGH-ELL*table.

The spectra give $D_\ell = \ell(\ell+1)C_\ell / 2\pi$ in units of $\mu\, K^2$, and the covariance matrix is in units of $\mu\, K^4$.

The CMB spectrum is also given in a simple text comma-separated file:

## Likelihood[edit]

TO BE WRITTEN.

## References[edit]

- ↑
^{1.0}^{1.1}^{1.2}**Planck 2013 results. XI. Component separation**, Planck Collaboration, 2014, A&A, 571, A11 - ↑
^{2.0}^{2.1}^{2.2}**Planck 2015 results. XI. CMB power spectra, likelihoods, and robustness of cosmological parameters**, Planck Collaboration, 2016, A&A, 594, A11. - ↑
^{3.0}^{3.1}^{3.2}^{3.3}^{3.4}**Planck 2015 results. XIII. Cosmological parameters**, Planck Collaboration, 2016, A&A, 594, A13. - ↑
^{4.0}^{4.1}**Planck 2013 results. XV. CMB power spectra and likelihood**, Planck Collaboration, 2014, A&A, 571, A15 - ↑
**Planck 2015 results. VII. High Frequency Instrument data processing: Time-ordered information and beam processing**, Planck Collaboration, 2016, A&A, 594, A7.

Cosmic Microwave background

Flexible Image Transfer Specification