maps_manip - Manipulate maps

powspechi.maps_manip.getsupmapiso(nside, etacut=0.9)

Get the desired supmap_iso.

Parameters

• nside (int, scalar) – Map resolution.

• etacut (float, scalar, optional) – The imposed limit to pseudorapidity, such that \(|\eta|\) < etacut. Default: 0.9.

Returns

supmapiso – A 1-D array representing a HEALPix map with the specified resolution.

Return type

float, ndarray

Raises

IsomapError – If the supmap_iso*.fits file does not exist.

Notes

The maps in the files supmap_iso*.fits are meant to correct for edge effects when there is a limit on \(\eta\) (\(\theta\)) and it is necessary to divide the event maps their ensemble sum. In the case of no \(\theta\) limitations or no divisions, such maps are not necessary. Currently, powspechi supports such corrections for nside: 8, 16, 32, 64 and 128 and etacut: 0.8 and 0.9.

powspechi.maps_manip.make_normmaps(maps, supmap, etacut=0.9)

Divide an ensemble of maps by a single map, preferably the sum of said ensemble.

Parameters

• maps (float, array_like) – A single map or an ensemble of maps. They should be limited in pseudorapidity by the value in etacut.

• supmap (float, ndarray) – A 1-D array usually representing the sum of all elements in maps.

• etacut (float, scalar, optional) – The value of the pseudorapidity limit, \(|\eta|\) < etacut. If there is no limit, set it to None. Default: 0.9.

Returns

norm_maps – The result of dividing maps by supmap. Its shape will be the same as maps.

Return type

float, array_like

Notes

In the power spectral analysis at hand 1 2, supmap is the sum of all event maps and it is represented by \(F^{all}(\mathbf{n_p})\), where \(\mathbf{n_p}\) is a pixel number. A normalized map is thus defined by the following expression:

\[\bar{f}(\mathbf{n_p}) = \frac{f(\mathbf{n_p})}{F^{all}(\mathbf{n_p})},\]

where \(f(\mathbf{n_p})\) is a map from the original event ensemble, the latter denoted by the maps parameter.

References

1

13. Machado, P.H. Damgaard, J.J. Gaardhoeje, and C. Bourjau, “Angular power spectrum of heavy ion collisions”, Phys. Rev. C 99, 054910 (2019).

2

13. Machado, “Heavy ion anisotropies: a closer look at the angular power spectrum”, arXiv:1907.00413 [hep-ph] (2019).

powspechi.maps_manip.mapping(nside, angs)

Make a map with a chosen resolution out of particles angular coordinates \((\phi, \theta)\).

Parameters

• nside (int, scalar) – Chosen map resolution.

• angs (float, ndarray) – A 2-D array whose first column corresponds to the \(\phi\) coordinate while the second corresponds to the \(\theta\) coordinate.

Returns

maph – A 1-D array whose size depends on the nside through the relation \(\mathrm{len(maph)} = 12 \cdot nside^2\).

Return type

float, ndarray

powspechi.maps_manip.readevtfile(infile, skip_header=True)

Read an event file with at least two columns, where the first should correspond to the particles’ azimuthal (\(\phi\)) coordinates and the second to the polar (\(\theta\)) coordinates.

Parameters

• infile (filenamestr) – The event file name whose format is described above.

• skip_header (bool, optional) – Option to skip the first line of the file. Default: True.

Returns

angs – A 2-D array whose shape is (mult, ncol), where mult is the event multiplicity and ncol the number of columns.

Return type

float, ndarray

powspechi.maps_manip.supmaps(maps, supmapiso=None)

Sum an ensemble of maps.

Parameters

• maps (float, array_like) – A map or a list/array of maps.

• supmapiso (float, ndarray, optional) – A map limited in \(\theta\), used to account for the pixel weights on map edges. Default: None.

Returns

supmap – A 1-D array resultant of the sum of the elements in maps. If supmapiso is given, weights are assigned to the pixels on the edges of supmap.

Return type

float, ndarray