nmfwisp 1.1.0

Subtract wisp artifacts in JWST NIRCam images with the non-negative matrix factorization (NMF) algorithm

Purpose

This package subtracts wisps from JWST/NIRCam images using data-driven, multi-component wisp templates.

Wisps are scattered light artifacts in JWST NIRCam images. They usually appear in the same locations on NIRCam detectors with mild morphological variation between observations. Wisps are a significant source of contamination for objects fainter than 25 AB mag.

We construct detector- and filter-specific wisp templates using the Non-negative Matrix Factorization (NMF) algorithm, based on extensive NIRCam data from JADES and other programs. This algorithm efficiently extracts wisp morphology and its principal modes of variations. The NMF-derived templates yield substantial improvement in wisp subtraction compared to existing single-template approaches

Implementation

Wisp subtraction should be applied at Stage 2 of the JWST data reduction pipeline. For a single NIRCam detector, the runtime is about 0.4 seconds per exposure on one CPU core of an Apple M4 Pro. The runtime is 2 seconds when performing joint fitting with 1/f noise.

The main interface is the fit_wisp function in nmfwisp.py, which returns the best-fit wisp model and its uncertainty. The package distributes the template library directly as package data, so users can run with the default bundled templates immediately after installation.

The bundled templates make the package relatively large (compressed templates are about 80 MB).

The developer directory contains code used to build the wisp template library.

Installation

Install from PyPI:

pip install nmfwisp

For development install from source:

git clone https://github.com/zihaowu-astro/NMFwisp.git
cd NMFwisp
pip install -e .

Example

from astropy.io import fits
import matplotlib.pyplot as plt
import numpy as np

filter_name = 'F150W'
detector_name = 'nrcb4'

# Example file
filename = './data/jw01286001001_07201_00003_nrcb4_rate.fits'
maskfile = './data/jw01286001001_07201_00003_nrcb4_cal_bkgsub_tweak_smask-full.fits'

data = fits.open(filename)['SCI'].data
err  = fits.open(filename)['ERR'].data
mask = fits.open(maskfile)[0].data

# Fit wisps
from nmfwisp import fit_wisp
wisp, wisp_e = fit_wisp(
    data, err, mask,
    detector_name=detector_name,
    filter_name=filter_name,
    correct_1f=False
)

To use a custom template library path instead of bundled templates:

wisp, wisp_e = fit_wisp(
    data, err, mask,
    wisp_path='/path/to/templates',
    detector_name=detector_name,
    filter_name=filter_name,
    correct_1f=False
)

Visualization of the wisp subtraction result:

data0 = np.nan_to_num(data, nan=0.0) # remove nan values
fig, ax = plt.subplots(1, 3, figsize=(10, 4))
vmin, vmax = np.nanpercentile(data, 5), np.nanpercentile(data, 95)
ax[0].imshow(data0, origin='lower', vmin=vmin, vmax=vmax)
ax[0].set_title('Data')
ax[1].imshow(data0 - wisp, origin='lower', vmin=vmin, vmax=vmax)
ax[1].set_title('Data - WISP')
ax[2].imshow(wisp, origin='lower', vmin=0, vmax=np.nanpercentile(wisp, 99))
ax[2].set_title('WISP')
for a in ax:
    a.axis('off')
plt.tight_layout()
plt.show()

Wisp Morphology

Citation

If you use this code, please reference this paper:

@ARTICLE{2026arXiv260115958W,
       author = {{Wu}, Zihao and {Johnson}, Benjamin D. and {Eisenstein}, Daniel J. and {Cargile}, Phillip and {Hainline}, Kevin and {Hausen}, Ryan and {Rinaldi}, Pierluigi and {Robertson}, Brant E. and {Tacchella}, Sandro and {Williams}, Christina C. and {Willmer}, Christopher N.~A.},
        title = "{JWST Advanced Deep Extragalactic Survey (JADES) Data Release 5: Wisp Subtraction with the Non-negative Matrix Factorization Algorithm}",
      journal = {arXiv e-prints},
     keywords = {Instrumentation and Methods for Astrophysics, Astrophysics of Galaxies},
         year = 2026,
        month = jan,
          eid = {arXiv:2601.15958},
        pages = {arXiv:2601.15958},
          doi = {10.48550/arXiv.2601.15958},
archivePrefix = {arXiv},
       eprint = {2601.15958},
 primaryClass = {astro-ph.IM},
       adsurl = {https://ui.adsabs.harvard.edu/abs/2026arXiv260115958W},
      adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}