clean#
- xrayvision.clean.clean(dirty_map, dirty_beam, pixel_size=None, clean_beam_width=<Quantity 4. arcsec>, gain=0.1, thres=None, niter=5000)[source]#
Clean the image using Hogbom’s original method.
CLEAN iteratively subtracts the PSF or dirty beam from the dirty map to create the residual. At each iteration, the location of the maximum residual is found and a shifted dirty beam is subtracted at that location. This process continues until either
niteriterations are reached or the maximum residual <=thres.- Parameters:
dirty_map (Quantity) – The dirty map to be cleaned 2D
dirty_beam (Quantity) – The dirty beam or point spread function (PSF) 2D must
pixel_size (Quantity) – The pixel size in arcsec
clean_beam_width (Quantity | None) – The width of the gaussian to convolve the model with. If set to 0.0 the gaussian to convolution is disabled
gain (float | None) – The gain per loop or loop gain
thres (float | None) – Terminates clean when
residual.max() <= thresniter (int) – Maximum number of iterations to perform
- Returns:
The CLEAN image 2D
- Return type:
Notes
The CLEAN algorithm can be summarised in pesudo code as follows:
\[\begin{split}& \textrm{CLEAN} \left (I^{D}(l, m),\ B(l,m),\ \gamma,\ f_{Thresh},\ N \right ) \\ & I^{Res} = I^{D},\ M = \{\},\ i=0 \\ & \textbf{while} \ \operatorname{max} I^{Res} > f_{Thresh} \ \textrm{and} \ i \lt N \ \textbf{do:} \\ & \qquad l_{max}, m_{max} = \underset{l,m}{\operatorname{argmax}} I^{Res}(l,m) \\ & \qquad f_{max} = I^{Res}(l_{max}, m_{max}) \\ & \qquad I^{Res} = I^{Res} - \alpha \cdot f_{max} \cdot \operatorname{shift} \left ( B(l,m), l_{max}, m_{max} \right ) \\ & \qquad M = M + \{ l_{max}, m_{max}: \alpha \cdot f_{max} \} \\ & \qquad i = i + 1 \\ & \textbf{done} \\ & \textbf{return}\ M,\ I^{Res}\end{split}\]