RAT_S–SPARC: Version 4 Analysis Archive for an Empirical Fast-Saturating Two-Parameter Description of SPARC Galaxy Rotation Curves

Abstract

This Version 4 archive accompanies the manuscript “An empirical fast-saturating two-parameter description of SPARC galaxy rotation curves”. It contains the formula-rendered MNRAS manuscript and supplementary material, editable DOCX and machine-readable Markdown/HTML sources, eight Python analysis scripts, six recorded result reports, five CSV analysis tables, and 13 analysis figures. The study compares six two-parameter saturating functions as empirical descriptions of the additional velocity contribution in 175 SPARC disc galaxies. The selected RAT_S form is the fast-saturating rational parameterisation V_extra = v0 r^2 / (r^2 + k^2). The archive preserves the completed Wilcoxon signed-rank tests, sign tests, bootstrap analysis, repeated random hold-out evaluation, jackknife analysis, subsample analysis, parameter-boundary tests, and failure diagnostics without changing the models or recorded numerical results. In the recorded tables, the mean BIC is 959.78 for RAT_S, 1001.99 for EXP, and 982.26 for the adopted prior-regularised cored-NFW benchmark. RAT_S is presented as an empirical and phenomenological description of the present SPARC sample. The comparison with the adopted ΛCDM implementation is conditional on the stated priors and does not constitute a claim about cosmology, dark matter, or modified gravity. Validation on independent rotation-curve samples remains necessary. The raw official SPARC rotation-model inputs (*.dat files with the *_rotmod.dat naming convention) were not present in the audited project tree and are therefore not redistributed in this archive. A clean-room rerun requires obtaining the corresponding SPARC data package from the official project source, placing the files in the SPARC_data directory expected by the scripts, and recording the input version and checksums. The derived tables and reports are included exactly as supplied. An optional Chinese Version 2 companion is included for reader convenience. The English manuscript and supplementary material are authoritative.