kyuen2 / LazDDA

The source code for the Velocity Decomposition Algorithm (Yuen et.al ApJ 910, 161 2021).

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LazDDA: The Velocity Decomposition Algorithm

The source code for the Velocity Decomposition Algorithm (Yuen et.al ApJ 910, 161 2021).

What is the physics?

We aim to separate the non-density similar fluctuations in spectroscopic channel maps. Therefore we developed a very simple similarity algorithm, supported by our paper with turbulence theory and MHD simulations, that the $p_v$ computed according to our formula might correspond to something called "velocity caustics" predicted by theory (Lazarian & Pogosyan 2000).

Computationally what is it about?

The code allows you to compute the p_d and p_v based on the cross-correlation of two images p and I. By the definition of Eq.(20) of Yuen et.al (2021),

Yuen et.al (2021) Eq.20

where <...> is the averaging operator. Notice that <p_d p_v> is mathematiclly guaranteed to be zero, regardless of what p and I it is.

For example, suppose we allow

Below we trimmed these two figures so that they are in greyscale and have same dimensions. Here we show the p and I before our algorithm:

The definition of p and I of our method

and the results of our algorithm

p_d and p_v according to our method

We have to remind our readers that, under our construction <p_d p_v> must be zero, no matter what p and I you are considering. Below shows no matter what fractions cats and dogs in your image

mean(pd*pv)=0

This is guaranteed by the mathematics, regardless of what p and I one is considering (see our latest response in https://github.com/kyuen2/kalberla_2022)

proof

About

The source code for the Velocity Decomposition Algorithm (Yuen et.al ApJ 910, 161 2021).

License:MIT License


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