Faint Residual Masking Application on Taurus and California
By Elijah Bernstein-Cooper, July 16, 2015, 0 comments.

## Likelihood Results

Figure 1. - Perseus likelihoods.

Figure 2. - California likelihoods. The tiny $HI$ width is worrying. In an attempt to address this strange behavior, I performed a 2D background fit on California outlined in this post. This narrow $HI$ width is because the model is finding a high intercept fits best, while only a small component of $HI$ emission correlates with the dust. The model believes that there is little dust which is associated with the clouds $HI$.

The unmasked region used to fit the model is the diffuse, low-$A_V$ south-east region of California. See later in the post for the progression of masks.

Figure 3. - California likelihoods with a background subtraction. This looks pretty bad. Not sure what is going on here.

Figure 4. - Taurus likelihoods. The model is favoring to include the entire line of sight from Taurus. This seems reasonable, though is completely different from what we were finding earlier.

Below are a progression of masked residual maps and residual histograms for each iteration. ‘mask iter’ refers to each iteration in the masking, ‘parent iter’ refers to an entire run through masking and the MLE calculation. The first mask, ‘mask iter = 0’, for each parent iteration should be the same, since these are only the faintest 10% of the pixels without any other masking applied.

We’re testing convergence of the DGR during masking outlined in the last post.

Figure 8. - Perseus parameter convergences.

Figure 8. - California parameter convergences. The DGRs are leveling off, as we would expect.

Figure 8. - Taurus parameter convergences. There is something obviously wrong here. The $HI$ width in the second iteration, $\Delta_V = 70$ km/s, should yield the same results as the first iteration, since there is no difference between them. This is a bug.

## Multiprocessing

The likelihood calculation now includes multiprocessing framework. This speeds up the calculation by around 50% per additional CPU. See this version of cloudpy. Bip has 12 CPUs, so the speed increase is notable.