Skymap

class erwans3.Astro_tools.Skymap(map: ~typing.Union[~erwans3.Astro_tools.PixList, ~erwans3.Astro_tools.SHCoeff, ~astropy.units.quantity.Quantity], frame: ~astropy.coordinates.baseframe.BaseCoordinateFrame = <ICRS Frame>, time: ~typing.Optional[~astropy.time.core.Time] = None, freq: ~typing.Optional[~astropy.units.quantity.Quantity] = None, spectral_index: ~typing.Optional[~typing.Union[float, ~erwans3.Astro_tools.PixList, ~erwans3.Astro_tools.SHCoeff]] = None, spectral_range_validity: ~typing.Optional[tuple[astropy.units.quantity.Quantity, astropy.units.quantity.Quantity]] = None, polar: str = 'I')

Bases: object

Represents a map of the sky with contextual information such as time, frequency, polarization, and frame.

A spectral index can be associated as well (either as a scalar or as a map)

Parameters:

map (PixList or SHCoeff or Quantity) – The map data represented as a PixList subclass or SHCoeff. If map is a Quantity, it is assumed to be a HEALPix map.
frame (BaseCoordinateFrame, optional) – The coordinate frame associated with the map. Defaults to ICRS.
time (Time or None, optional) – The time associated with the map. Defaults to None.
freq (Quantity [Hz], None, optional) – The frequency associated with the map. Defaults to None.
spectral_index (float or PixList or SHCoeff or None, optional) – The spectral index associated with the map. Defaults to None.
spectral_range_validity (tuple [Quantity [Hz], Quantity [Hz]], optional) – The validity range of the spectral index. Defaults to (0, inf).
polar (str, optional) – The polarization information. Defaults to ‘I’.

map

The map data in PixList, SHCoeff, or HpxMap format.

Type:: PixList or SHCoeff

frame

The coordinate frame associated with the map.

Type:: BaseCoordinateFrame

time

The time associated with the map.

Type:: Time

freq

The frequency associated with the map.

Type:: Quantity [Hz]

spectral_index

The spectral index associated with the map.

Type:: float or PixList or SHCoeff or None

spectral_range_validity

The validity range of the spectral index.

Type:: tuple [Quantity [Hz], Quantity [Hz]]

polar

The polarization information.

Type:: str

Notes

If the input map is already a Skymap instance, the new instance will be a copy of that Skymap.
If frame is not provided, it defaults to the ICRS coordinate frame.
If time is not provided but can be inferred from frame.obstime, it is automatically set.
The spectral_index can be a scalar value, a PixList, SHCoeff, or HpxMap depending on the map type.
The spectral_range_validity tuple defines the validity range for the spectral index.
The default polarization mode is ‘I’ (total intensity).

Attributes Summary

`map_style`	Return the type of map data (SHCoeff or Pixmap).
`simu_type`	Return the simulation type based on the map style.
`unit`	Return the unit of the skymap data.

Methods Summary

`b2t`([copy, rj])	Convert brightness to temperature using the associated frequency of the skymap.
`change_freq`(new_freq[, copy])	Change the frequency of the Skymap by applying a power law with the provided spectral index.
`change_map_style`(new_class[, copy])	Change the class of the stored map and spectral index.
`get_skymap`([freq, frame, simu])	Return a new Skymap object with the desired frequency, frame, and map style.
`match_other`(other)	Compares this Skymap object with another Skymap and returns a tuple of boolean values indicating which criteria match between the two Skymap objects.
`plot`(**kwargs)	Plot the skymap using the plot method of the underlying map object.
`t2b`([copy, rj])	Convert temperature to brightness per steradian using the associated frequency of the skymap.
`to_extensive`([copy])	Convert the skymap to an extensive representation.
`to_intensive`([copy])	Convert the skymap to an intensive representation.
`transform_to`(new_frame[, copy])	Change Frame / Orientation (equivalent to rotate for maps)
`ud_grade`(nside_out[, copy])	Upgrade or downgrade the resolution of the skymap to the specified nside value.

Attributes Documentation

map_style

Return the type of map data (SHCoeff or Pixmap).

Returns:: The type of map data.
Return type:: type

simu_type

Return the simulation type based on the map style.

Returns:: The simulation type, either ‘SH’ for SHCoeff or ‘pixmap’ for Pixmap.
Return type:: str

unit

Return the unit of the skymap data.

Returns:: The unit of the skymap data.
Return type:: UnitBase

Methods Documentation

b2t(copy: bool = True, rj: bool = False) → Skymap

Convert brightness to temperature using the associated frequency of the skymap.

If Rayleigh-Jeans is assumed, the spectral index is changed as well. otherwise, the returned skymap will not have a spectral index

Parameters:

copy (bool, optional) – If True, return a new Skymap object with brightness converted to temperature. If False, modify the current Skymap object in place. Default is True.
rj (bool, optional) – If True, assume Rayleigh-Jeans approximation (spectral index is changed accordingly). If False, the returned Skymap will not have a spectral index. Default is False.

Returns:

If copy is True, returns a new Skymap object with brightness converted to temperature. If copy is False, modifies in place.

Return type:

Skymap

change_freq(new_freq: Quantity, copy: bool = True) → Skymap

Change the frequency of the Skymap by applying a power law with the provided spectral index.

Parameters:

new_freq (Quantity [Hz]) – The new frequency to change to, specified with appropriate units.
copy (bool, optional) – If True, returns a new Skymap with the frequency changed. If False, modifies the existing Skymap in place.

Returns:

If copy is True, returns a new Skymap object with the updated frequency. If copy is False, modifies and returns the existing Skymap object with the updated frequency.

Return type:

Skymap

Raises:

ValueError – If the new frequency is outside the specified spectral range validity.

Notes

If no spectral index is provided, nothing changes in the Skymap.
Upcoming: handle spectra function map

change_map_style(new_class: type, copy: bool = True, **kwargs) → Skymap

Change the class of the stored map and spectral index.

Parameters:

new_class (type) – The new class type to convert the map and spectral index to.
copy (bool, optional) – If True, returns a copy of the Skymap with the updated map style. If False, modifies the current Skymap in place.
**kwargs – Additional keyword arguments to pass to the conversion function.

Returns:

A new Skymap object with the updated map and spectral index classes if copy=True. Otherwise, modifies and returns the current Skymap in place.

Return type:

Skymap

Notes

The method uses the change_map_style() function internally to convert the map and spectral index.
The is_map() function is used to check if the spectral index is a valid map.

get_skymap(freq: Optional[Quantity] = None, frame: Optional[Union[BaseCoordinateFrame, SkyCoord]] = None, simu: bool = True) → Skymap

Return a new Skymap object with the desired frequency, frame, and map style.

Parameters:

freq (Quantity [Hz] or None, optional) – The desired frequency for the Skymap. If None, the frequency remains unchanged.
frame (BaseCoordinateFrame or SkyCoord None, optional) – The desired frame or observer for the Skymap. If None, the frame remains unchanged.
simu (bool, optional) – Whether to simulate the Skymap with the desired map style based on the simu_type attribute.

Returns:

A new Skymap object with the specified frequency, frame, and map style.

Return type:

Skymap

Notes

If freq or frame is specified, the returned Skymap will have the updated frequency or frame.
If simu is True, the returned Skymap will be simulated with the desired map style based on simu_type.

match_other(other: Skymap) → tuple[bool]

Compares this Skymap object with another Skymap and returns a tuple of boolean values indicating which criteria match between the two Skymap objects.

return a list of boolean saying which criteria matches between 2 Skymap object

Parameters:: other (Skymap) – Another Skymap object to compare with.
Returns:: :obj:`~tuple` [ – A tuple of boolean values indicating the matching criteria: - Unit compatibility. - Time information. - Polarization information. - Frequency information. - Map style compatibility (PixList, SHCoeff).
Return type:: obj`~:bool`]

Notes

unit_bool: True if the physical unit types of the two Skymaps match, False otherwise.
time_bool: True if both Skymaps have valid time information and it matches, False otherwise.
freq_bool: True if both Skymaps have valid frequency information and it matches, False otherwise.
polar_bool: True if the polarization information of both Skymaps matches, False otherwise.
mapstyle_bool: True if the map style (PixList, SHCoeff) matches between the two Skymaps, False otherwise.
tot_bool: A tuple containing all individual boolean criteria.

plot(**kwargs)

Plot the skymap using the plot method of the underlying map object.

Parameters:: **kwargs – Additional keyword arguments to pass to the underlying map’s plot method.

Notes

This method forwards the plotting to the plot method of the underlying map object.

t2b(copy: bool = True, rj: bool = False) → Skymap

Convert temperature to brightness per steradian using the associated frequency of the skymap.

If Rayleigh-Jeans is assumed, the spectral index is changed as well. otherwise, the returned skymap will not have a spectral index

Parameters:

copy (bool, optional) – If True, return a new Skymap object with temperature converted to brightness. If False, modify the current Skymap object in place. Default is True.
rj (bool, optional) – If True, assume Rayleigh-Jeans approximation (spectral index is changed accordingly). If False, the returned Skymap will not have a spectral index. Default is False.

Returns:

If copy is True, returns a new Skymap object with temperature converted to brightness. If copy is False, modifies in place.

Return type:

Skymap

to_extensive(copy: bool = True) → Skymap

Convert the skymap to an extensive representation.

Parameters:: copy (bool, optional) – If True, return a new Skymap object with an extensive representation of the map. If False, modify the current Skymap object in place. Default is True.
Returns:: If copy is True, returns a new Skymap object with an extensive representation of the map. If copy is False, modifies in place.
Return type:: Skymap

to_intensive(copy: bool = True) → Skymap

Convert the skymap to an intensive representation.

Parameters:: copy (bool, optional) – If True, return a new Skymap object with an intensive representation of the map. If False, modify the current Skymap object in place. Default is True.
Returns:: If copy is True, returns a new Skymap object with an intensive representation of the map. If copy is False, modifies in place.
Return type:: Skymap

transform_to(new_frame: BaseCoordinateFrame, copy: bool = True) → Skymap

Change Frame / Orientation (equivalent to rotate for maps)

Parameters:

new_frame (BaseCoordinateFrame) – The new coordinate frame to transform the Skymap to.
copy (bool, optional) – If True, returns a new Skymap object with the transformation applied (default is True).

Returns:

If copy is True, returns a new Skymap object with the transformation applied. If copy is False, modifies the existing Skymap object in place and returns it.

Return type:

Skymap

Notes

If new_frame is a callable, it will be called to generate a new frame. If the new frame has a different obstime than the Skymap’s time, a new frame with the same attributes as the new frame but with the Skymap’s time will be created.
The rotation to transform the Skymap is determined by the composition of transformation matrices between the current frame and the new frame (comp_matrix_transfo() function is used).
The spectral_index attribute, if present and a map, will also be rotated along with the Skymap.