README for the stacked spectra of radio-excess sources

By Marina Arnaudova, Luke Holden & Dan Smith, July 2026

m.i.arnaudova@gmail.com l.holden@herts.ac.uk d.j.b.smith@herts.ac.uk

Description

The stacked spectra of LERGs, HERGs, radio excess sources that cannot be confidently separated into LERGs and HERGs (RX_Unc) and the total radio-excess population (RX; including the previous three classes) from Arnaudova et al. (2026) as a function Eddington-scaled accretion rate (λEdd​). The stacks were produced using SpecStacker (https://github.com/m-arnaudova/SpecStacker), an open-source spectral stacking code described by Arnaudova et al. (2024).

Each FITS file contains a set of stacked spectra binned as a function of λEdd. Each FITS extension corresponds to a different λEdd​ interval (e.g. -1.0<lambda_edd<-0.5) and stores the stacked spectrum for that bin. The table in each extension contains four columns:

• wln: the rest-frame wavelength (Angstrom);

• flux: the stacked flux density (arbitrary units);

• flux_err: the uncertainty on the stacked flux density (arbitrary units)

• N: the number of individual spectra contributing to the stack at each wavelength element.

Note: The spectra near the wavelength limits of each stack should be treated with caution and are not recommended for scientific analysis. These regions are affected by edge artefacts introduced during the resampling and stacking process and also contain contributions from relatively few spectra, as indicated by the corresponding values of N.