qhjqhj00 sersic-fit-mock-eval
The HST/ACS Coma Cluster Survey III. Structural Parameters of Galaxies using single-S'ersic Fits — Hoyos et al. (2010) (arXiv:1010.2352, 2010)
What this evaluates
Evaluates the accuracy and robustness of Sérsic profile fitting algorithms (GIM2D and GALFIT) on simulated HST/ACS galaxy images. It probes how well these codes recover true structural parameters under varying signal-to-noise ratios and surface brightness levels.
Datasets
- GEMS Bulge0001 — total 558; splits: test (558)
- GEMS Disk0001 — total 470; splits: test (470)
Metrics
magnitude_residual(primary) — range: mag- Fitted total magnitude minus the true simulated magnitude.
effective_radius_ratio— range: ratio- Fitted effective radius divided by the true effective radius.
sersic_index_error— range: index- Fitted Sérsic index minus the true Sérsic index.
Input / output format
Input: Simulated HST/ACS images containing artificial galaxies with known pure Sérsic profiles (n=1 or n=4), embedded in Poisson noise and real sky background patches.
Output: Fitted structural parameters: total magnitude, effective radius, Sérsic index, and sky background level.
Scoring recipe
# For each simulated galaxy:
true_mag, true_re, true_n = get_true_parameters(simulation)
fit_mag, fit_re, fit_n = get_fitted_parameters(model)
magnitude_residual = fit_mag - true_mag
re_ratio = fit_re / true_re
n_error = fit_n - true_n
# Aggregate across dataset:
scatter_mag = std(magnitude_residual)
scatter_re = std(re_ratio)
# Analyze trends vs true surface brightness
Common pitfalls
- Inaccurate sky determination is the dominant source of parameter recovery errors.
- Default cutout sizes cause systematic offsets in magnitude and effective radius at faint surface brightness levels.
- Failing to mask overlapping sources increases scatter in fitted parameters.
Evidence (verbatim from paper)
The upper panel presents the magnitude residual (GIM2D minus Model), the middle panel presents the ratio in effective radii, and the lower panel presents the output Sérsic index as a function of the average surface brightness within a effective radius of the simulation.
Citation
@misc{hoyos2010hstacs,
title={The HST/ACS Coma Cluster Survey III. Structural Parameters of Galaxies using single-S'ersic Fits},
author={Hoyos et al. (2010)},
year={2010},
note={arXiv:1010.2352}
}
- arXiv: 1010.2352