swMATH ID: 29005
Software Authors: Peter Erwin
Description: Imfit: A Fast, Flexible New Program for Astronomical Image Fitting. I describe a new, open-source astronomical image-fitting program called Imfit, specialized for galaxies but potentially useful for other sources, which is fast, flexible, and highly extensible. A key characteristic of the program is an object-oriented design which allows new types of image components (2D surface-brightness functions) to be easily written and added to the program. Image functions provided with Imfit include the usual suspects for galaxy decompositions (Sersic, exponential, Gaussian), along with Core-Sersic and broken-exponential profiles, elliptical rings, and three components which perform line-of-sight integration through 3D luminosity-density models of disks and rings seen at arbitrary inclinations. Available minimization algorithms include Levenberg-Marquardt, Nelder-Mead simplex, and Differential Evolution, allowing trade-offs between speed and decreased sensitivity to local minima in the fit landscape. Minimization can be done using the standard chi^2 statistic (using either data or model values to estimate per-pixel Gaussian errors, or else user-supplied error images) or Poisson-based maximum-likelihood statistics; the latter approach is particularly appropriate for cases of Poisson data in the low-count regime. I show that fitting low-S/N galaxy images using chi^2 minimization and individual-pixel Gaussian uncertainties can lead to significant biases in fitted parameter values, which are avoided if a Poisson-based statistic is used; this is true even when Gaussian read noise is present.
Homepage: https://www.mpe.mpg.de/~erwin/code/imfit/
Source Code:  https://github.com/perwin/imfit
Dependencies: C++
Keywords: Astronomical Image Fitting; Astrophysics; arXiv_astro-ph.IM; Galaxies; arXiv_astro-ph.GA; photometry
Related Software: FFTW; BUDDA; GALFIT; GIM2D; NumPy; SCons; CxxTest; CFITSIO; MPFIT; NLopt; Sherpa; MGE; GALMORPH; ELLIPSE; LaplaceApproximation; cmaes; LaplacesDemon; R2Cuba; Python; GASPHOT
Cited in: 0 Documents

Standard Articles

1 Publication describing the Software Year
Imfit: A Fast, Flexible New Program for Astronomical Image Fitting arXiv
Peter Erwin