Comments (1)
Emma Alexander and I have noticed that the "noise" in RM cubes has very nasty properties, e.g. apparently randomly varying from pixel to pixel despite the maps being oversampled, and often with higher values than on-source. That is, sources of genuine polarized emission appear as islands of low polarized intensity surrounded by random spikes of much higher polarized intensity in off-source pixels. We attribute this to deriving spectra from (Q/I) and (U/I) where I is a non-significant quantity that frequently passes through zero. The solution to this would be to divide by a model power-law fitted to the I values rather than the raw values. We think this would also stabilise the RM-fitting where there is genuine signal of relatively low significance. A model power law would by definition not change sign. In regions of noise the amplitude will often be negative but that does not matter since there is actually no signal and we are only interested in the noise. On-source, a power-law fit would nearly always be an adequate approximation for data taken in a single band, covering a few hundred MHz. For fitting over larger spectral ranges the best approach would be a low-order polynomial in log-log space: the order of polynomial could be one of the input parameters. Obviously fitting a power law would require a non-linear least-squares fit, but this can be done efficiently by initially doing a linear least-squares fit in log-log space and using the results as the starting estimate for the non-linear fit.
from rm-tools.
Related Issues (20)
- nufft dtype error HOT 6
- 3D cube writer breaks if BUNIT doesn't exist
- Automatic PyPI publishing HOT 5
- Stokes I fitting threshold
- Stokes I renormalisation failure case
- rmsynth3d imaginary FDF files have wrong Stokes axis values HOT 2
- RMSF helper script is bugged
- do_fitIcube: tqdm.contrib.concurrent doesn't play nicely with Prefect
- rescale_I_model_3D: rescale_I_pixel uses a dictionary but util_misc.renormalize_StokesI_model expects "FitResult" class HOT 2
- Cannot reshape array of size ******......After calculating the FDF anf RMSF HOT 4
- Input a bad channel list (3D tools)
- Dtypes change in do_fitIcube.py rescale_I_model_3D.py
- peakfitcube tool fails with index error HOT 4
- rmtools_peakfitcube fails with all-NaN maps as output HOT 2
- error message 'ValueError: not enough values to unpack (ecpected 4, got 3)' in rmclean3d HOT 7
- QU-fitting PA uncertainty does not take angle wrapping into account HOT 5
- Release Numpy restriction? HOT 2
- Progress bar for do_fitIcube reverted to old style HOT 3
- Convert Stokes I model to same reference frequency as polarization HOT 1
- Deprecation and versioning notes HOT 1
Recommend Projects
-
React
A declarative, efficient, and flexible JavaScript library for building user interfaces.
-
Vue.js
🖖 Vue.js is a progressive, incrementally-adoptable JavaScript framework for building UI on the web.
-
Typescript
TypeScript is a superset of JavaScript that compiles to clean JavaScript output.
-
TensorFlow
An Open Source Machine Learning Framework for Everyone
-
Django
The Web framework for perfectionists with deadlines.
-
Laravel
A PHP framework for web artisans
-
D3
Bring data to life with SVG, Canvas and HTML. 📊📈🎉
-
Recommend Topics
-
javascript
JavaScript (JS) is a lightweight interpreted programming language with first-class functions.
-
web
Some thing interesting about web. New door for the world.
-
server
A server is a program made to process requests and deliver data to clients.
-
Machine learning
Machine learning is a way of modeling and interpreting data that allows a piece of software to respond intelligently.
-
Visualization
Some thing interesting about visualization, use data art
-
Game
Some thing interesting about game, make everyone happy.
Recommend Org
-
Facebook
We are working to build community through open source technology. NB: members must have two-factor auth.
-
Microsoft
Open source projects and samples from Microsoft.
-
Google
Google ❤️ Open Source for everyone.
-
Alibaba
Alibaba Open Source for everyone
-
D3
Data-Driven Documents codes.
-
Tencent
China tencent open source team.
from rm-tools.