SkyShell

class gammapy.image.models.SkyShell(lon_0, lat_0, radius, width)

Bases: gammapy.image.models.SkySpatialModel

Shell model

\[\begin{split}\phi(lon, lat) = \frac{3}{2 \pi (r_{out}^3 - r_{in}^3)} \cdot \begin{cases} \sqrt{r_{out}^2 - \theta^2} - \sqrt{r_{in}^2 - \theta^2} & \text{for } \theta \lt r_{in} \\ \sqrt{r_{out}^2 - \theta^2} & \text{for } r_{in} \leq \theta \lt r_{out} \\ 0 & \text{for } \theta > r_{out} \end{cases}\end{split}\]

where \(\theta\) is the sky separation and \(r_out = r_in\) + width

Note that the normalization is a small angle approximation, although that approximation is still very good even for 10 deg radius shells.

Parameters:

lon_0 : Longitude

\(lon_0\)

lat_0 : Latitude

\(lat_0\)

radius : Angle

Inner radius, \(r_{in}\)

width : Angle

Shell width

Methods Summary

__call__(lon, lat)	Call evaluate method
copy()	A deep copy.
evaluate(lon, lat, lon_0, lat_0, radius, width)	Evaluate the model (static function).

Methods Documentation

__call__(lon, lat)

Call evaluate method

copy()

A deep copy.

static evaluate(lon, lat, lon_0, lat_0, radius, width)

Evaluate the model (static function).