<figure><img src="image_32.png" /><figcaption>Fig. A.3: VIS image of the dual lensed AGN candidate SDSS J032023.93+412131.5 at $z = 2.811$, showing the nearby companion at 0.65 of separation. The contours show two fitted PSFs.</figcaption></figure>

model, whilst also accounting for the point-source residual. In the right panel of Fig. A.2, we show the implied point-source luminosity for each cluster member galaxy, integrated over the $I_E$ band, against their host's absolute magnitudes from the bulge and disc components. We are able to isolate two sub-samples, one within the same luminosity-magnitude range of the X-ray sources, and another low-mass sample with high luminosity. The measurement reliability and nature of the emission of all luminous point sources will be determined in a future paper.

## Appendix A.13. Dual/lensed QSO candidates at sub-arcsecond separations

During their life, galaxies experience a number of major and minor mergers with other galaxies. The supermassive black holes (SMBHs) present in the centres of most massive galaxies merge together with their hosts, creating a SMBH pair that slowly reduces its separation and eventually merges, creating a burst of gravitational waves (GW; e.g. Colpi 2014). During the in-spiralling phase, which can last gigayears (e.g. Volonteri et al. 2022), these pairs can be detected as dual AGN at kiloparsec separations.

The appearance of two or more QSOs at the same redshift and close separations can also be due to strong gravitational lensing of a single QSO due a foreground galaxy, producing multiple images of the background source. These are systems or great relevance in many fields of the astrophysics (e.g. Shajib et al. 2022).

Detecting these rare systems of dual or lensed QSOs is challenging because it requires high-resolution imaging over large parts of the sky, and only a small number of confirmed such systems have been discovered, especially outside the local universe (De Rosa et al. 2019; Mannucci et al. 2023). Recently, several techniques based on the ESA Gaia satellite have been proposed to select homogeneous samples of dual/lensed AGN candidates at sub-arcsecond separations (e.g. Lemon et al. 2017; Hwang et al. 2020; Mannucci et al. 2022). With its large FoV, superb spatial resolution, and high sensitivity, the Euclid VIS camera can outperform the previous techniques based on optical data

and provide large samples of dual/lensed AGN candidates, that is, AGN with nearby companions.

One such system have already been discovered by examining the eight known QSO with $z > 0.1$ covered by the VIS image of the Perseus cluster. One of them, SDSS J032023.93+412131.5, a QSO at $z = 2.811$ discovered by the SDSS (Lyke et al. 2020), shows a nearby companion at 0.65 of separation and 3.1 magnitude fainter than the primary component, see Fig. A.3. This system in unresolved in the Euclid NISP image, characterised by a much lower spatial resolution. Preliminary high-resolution NIR imaging with LBT (Ulivi et al., in prep), has revealed that the two objects have very similar optical-to-nearIR colours, indicating that the faint component is likely to be a secondary QSO in either a dual or a strongly lensed system. In the former case, the projected separation between the two component would be ~5.2 kpc.

## Appendix A.14. Properties of the interstellar medium: Albedo derivation from the optical to the NIR

The ERO Perseus data allow us to test the idea of using the Euclid images to study the structure of the Galactic interstellar medium (ISM) as well as the properties of interstellar dust. These micron-size solid particles absorb starlight, producing absorption, $A_V$, and reddening, $E(B-V)$, in the visible (and NIR), as well as a wide emission spectrum extending from the mid-IR to millimetre wavelengths. These signatures have been extensively used to understand the nature of interstellar dust, and also as tracers of the ISM structure. The underlying idea is that dust and gas are well mixed, in every phase of the ISM (Boulanger & Perault 1988).

In addition to absorption, a significant fraction of the starlight impinging on micron-size dust grains is scattered off their surfaces. Given their size and shape, the scattering is observed in the UV through the NIR, with an expected maximum around $\lambda = 1$ µm (Gordon 2004; Jones et al. 2017). This scattered light, historically dubbed diffuse Galactic light (DGL) has been known for several decades (Elvey & Roach 1937; Sandage 1976), but it is only recently that it has been used, such as absorption and emission, as a tracer of interstellar structure (Boissier et al. 2015; Miville-Deschênes et al. 2016; Mattila et al. 2018; Román et al. 2020; Liu et al. 2023). An important difference with emission and absorption is that the scattered light amplitude depends on the 3D structure of the radiation field because stellar photons are predominantly scattered in the forward direction. Therefore, in regions with very anisotropic radiation fields, the scattered light image will give a distorted picture of the interstellar density field. Fortunately most of the sky at high Galactic latitude is composed of diffuse interstellar clouds that are not forming stars and are illuminated by the general interstellar radiation field that can be considered to be close to isotropic. In this case, large area mapping of diffuse areas of the sky in the optical and NIR with very high angular resolution offers the opportunity to map the ISM structure down to AU scales over hundreds of parsecs.

The Perseus cluster field is a good test case for this. It is at intermediate latitude ($b = -13°$) with a moderate column density of $N_H \approx 1.4 \times 10^{21}$ cm$^{-2}$ using the $E(B-V) \approx 0.16$ estimate of Planck Collaboration XI (2014) in this area and the $E(B-V)/N_H$ conversion factor of Lenz et al. (2017). This corresponds to the translucent part of the interstellar medium ($A_V \approx 0.5$) where matter is expected to be mostly atomic. According to the THEMIS dust model (Jones et al. 2017), the dust scattering
should be maximum in the *Euclid* $J_E$ band. However, these theoretical estimates are based on very little data (see the review by Gordon 2004) and the exact shape of the scattered light spectrum should vary locally, since it contains information about dust shape, composition, and sizes. The combination of *Euclid*'s four bands, coupled with deep complementary optical *u*, *g*, *r*, *i*, and *z* ground-based CFHT data, provides a powerful wavelength range to study the DGL. In particular, combining scattering and emission offers a great opportunity to improve current dust models (e.g. Zhang et al. 2023).

# Appendix B: Structural parameters

## Appendix B.1. AutoProf and AstroPhot parameters

The photometry of galaxies identified as cluster members is carried out with AutoProf for the bright galaxies and a combination of AstroPhot and Galfit for the dwarf galaxies (Marleau et al. 2025). The codes are run on a limited portion of the image: the size of the cutouts varied for all the dwarfs depending on their effective radius, as described in Marleau et al. (2025). For the bright galaxies, the cutouts also varied in size, ranging from 1000 × 1000, 2000 × 2000, 4000 × 4000, and 8000 × 8000 VIS pixels, depending on their angular scale on the sky, the tile size being optimised to facilitate accurate sky background estimation. Only the two largest galaxies in the cluster, NGC 1272 and NGC 1275, required a tile size of 8000 × 8000 VIS pixels, as illustrated in Fig. B.1.

For the dwarf galaxies, the galaxy modelling was initially performed using AutoProf (Stone et al. 2021) to obtain a first estimate of the structural parameters. These initial estimates were then used as input to both Galfit (Peng et al. 2010) and AstroPhot (Stone et al. 2023). The details of the dwarf galaxy modelling procedure and results are presented in Marleau et al. (2025).

For the bright galaxy sample, after initially selecting galaxies based on their apparent size, a second sorting was conducted based on the proximity of the galaxies to each other. This proximity significantly influenced the choice of photometric extraction tool. AutoProf was utilised for relatively isolated galaxies, where their outermost isophotes do not significantly overlap with those of neighbouring galaxies. Conversely, AstroPhot is preferred for galaxies that are in close proximity to each other.

Once the tiles were extracted, the photometry of isolated galaxies was determined using the AutoProf tool. To minimise contamination from MW stars in the VIS photometry calculations, a star mask was created from each segmentation map generated by SourceExtractor. AutoProf then took this mask along with the galaxy image from the corresponding tile as inputs. AutoProf processed each galaxy to provide a detailed surface brightness profile, after fitting isophotes leading to an azimuthally averaged profile averaging the pixels along the isophotes. Output products included characteristic fit parameters such as sky background estimation, position angle, and mean ellipticity, among others. Figure B.1 displays examples of profiles generated by AutoProf. Additionally, a Sérsic model fit to the 1D profile was performed to derive the Sérsic index. Other photometric parameters extracted include total magnitude and effective radius, providing a comprehensive picture of each galaxy.

The remaining galaxies found in a crowded environment (i.e. 34 of the 137 bright galaxies) were analysed using the AstroPhot tool, which provides a range of modelling options. For these galaxies, simple Sérsic profiles were

initially fitted. Tiles of 4000 pixels × 4000 pixels were preferred, to ensure ample sky background for accurate photometry estimation in these complex areas. To initialise AstroPhot, star masking was conducted using the same approach as with AutoProf, employing segmentation maps and parameters from SourceExtractor, such as ellipticity, position angle, and estimated flux for each galaxy. Sérsic models were then initialised over 100 × 100 pixel windows, typically encompassing the galaxy's core. The process began with a first iteration using an iterative method to refine the model. This was followed by a second iteration that utilised the parameters from the first iteration but expanded the analysis to a 1000 × 1000 pixel window. Ultimately, a Sérsic profile was fit for each galaxy, detailing associated morphological and photometric parameters, as depicted in Fig. B.2. The results of the photometric analysis for bright galaxies are described in the tables of the Appendix C.

## Appendix B.2. Comparison with other codes

We first made a comparison of the SourceExtractor magnitudes extracted from the ring-filtered images and used in Sect. 7 with those measured using AutoProf/AstroPhot. The two sets of data agree within 0.1 mag, with a dispersion of 0.3. Since SourceExtractor magnitudes are consistently used to derive all the colours in the SED fitting procedure, we do not expect any major effect in the derivation of the stellar masses.

Other photometry software codes are available for comparison. In Stone et al. (2021), AutoProf has been compared to PHOTUTILS, XVISTA, and Galfit. In this appendix, an additional comparison is made with the Archangel pipeline (Schombert 2007; Schombert & Smith 2012) using the same specific *Euclid* ERO data. Previously, the Archangel software had been adapted for Spitzer space observations as described in detail in Sorce et al. (2012). For the comparisons in this appendix, it was further modified to be applied to *Euclid* data. Briefly, Archangel performs the masking of stars and flaws. Subsequently, it replaces masked regions by mean isophote values. Ellipses are then fit to isophotes with increasing radii. The 2D information is compressed into uni-dimensional surface brightness and magnitude growth curves. Other parameters such as extrapolated magnitudes, are finally derived. Archangel was run once on each galaxy of our test sample. We did not modify the parameters between elliptical, spiral, and dwarf galaxies so as not to bias the comparisons. In any case, Sorce et al. (2012) showed that the major contribution to the magnitude uncertainties for space-based observations is the setting of the sky level. Furthermore, Sorce et al. (2012) and Sorce et al. (2014) demonstrated the agreement between magnitudes obtained with the Spitzer-adapted version of Archangel and other alternative pipelines, such as the software developed for the GALEX Large Galaxy Atlas<fnref n="16" /> (GLGA, Seibert 2007) or for the Spitzer Survey of Stellar Structure in Galaxies (S⁴G, Sheth et al. 2010). The sky setting was identified as the cause of any difference between a few outliers.

Following the main analysis of the paper, the zero point is set to 30.13 (30) for the $I_E$ ($Y_E$, $J_E$, $H_E$) bands, the pixel size is 0.′1 and magnitudes are given in the AB system. In this appendix, detailed comparisons are presented for an elliptical, a spiral, and a dwarf galaxy, to emphasise the agreement between both software codes. Figure B.3 shows the surface brightness profile (blue solid and dashed lines) and the curve of growth (red solid and orange dashed lines) obtained for the three galaxies using

<footnote n="16">¹⁶ https://sites.astro.caltech.edu/~neill/GALEX/glga/</footnote>
<figure><img src="image_33.png" /></figure>

Fig. B.1: Examples of AutoProf radial profile extraction on VIS data to derive photometric and morphological properties. Top left: UGC 02665 isophote fitting on an 2000 pixel × 2000 pixel pixel cutout (200" × 200", red angular scale on the image: 30"). Top right: Radial surface brightness profile for UGC 02665, showing a dip at r = 60" due to overlap with neighbours, marking the photometry's limit. Bottom left: WISEAJ031858.26+414208.7 isophote fitting on a 2000 pixel × 2000 pixel cutout (200" × 200", red angular scale on the image: 30"). Bottom right: Radial surface brightness profile for NGC 1281, reaching down to 30.1 mag arcsec⁻² at r = 100" despite the proximity of a bright star. Cyan and red points on the radial profiles refer to the colours of isophotes in the associated AutoProf visual, which help guide the eye when comparing plots.

Archangel (solid lines) and AutoProf (dashed lines). There
is an agreement between the surface brightness profiles out to
the edges of the galaxies. The curves of growth tend to increase
faster with AutoProf but converge asymptotically to the same
magnitude as those obtained with Archangel. Axis ratios and
position angles derived with both codes are similar though.
The curves of growth thus differ only by the radius definition.
Table B.1 summarises the magnitudes in the four Euclid bands
obtained with both codes for the three galaxies, confirming the
agreement.

**Appendix C: Photometric tables of bright galaxies**

This section presents nine tables offering a complete overview of the catalogue, which is available as supplementary material at the Strasbourg astronomical Data Centre (CDS). The tables are as follows.

Table C.1: Complete list of parameters extracted for Tables C.3 to C.5, along with their descriptions and associated table indexes.

Table C.2: Complete list of parameters extracted for Tables C.6–C.9, along with their descriptions and associated table indexes.

Table C.3: primary data from VIS photometry.

Table C.4: associated errors for the primary data catalogue.

Table C.5: redshift and extinction corrections.

Table C.6: magnitudes within one effective radius ($R_e$) in VIS and NISP bands.

Table C.7: associated errors of the 1 $R_e$ magnitudes catalogue.

Table C.8: magnitudes using VIS photometry to constrain NISP photometry.

Table C.9: associated errors of the forced magnitudes.
<figure><img src="image_34.png" /><figcaption>Fig. B.2: Example of an AstroPhot fitting process on VIS data to derive photometric and morphological properties. Left: Input image (4000 pixel × 4000 pixel cutout, 400" × 400") featuring multiple overlapping galaxies from the Perseus cluster, namely NGC 1270, NGC 1268, NGC 1267, and CGCG540-089. Centre: Segmentation map of the image by SourceExtractor (scale in pixels). Right: Residual image (image minus models) for the initial fit, this gets substantially improved upon iterating.</figcaption></figure>

<table><caption>Table B.1: Magnitudes in the four Euclid bands.</caption><thead><tr><th rowspan="2">Name</th><th colspan="4">Archangel</th><th colspan="4">AutoProf</th></tr><tr><th>I<sub>E</sub></th><th>Y<sub>E</sub></th><th>J<sub>E</sub></th><th>H<sub>E</sub></th><th>I<sub>E</sub></th><th>Y<sub>E</sub></th><th>J<sub>E</sub></th><th>H<sub>E</sub></th></tr></thead><tbody><tr><td>UGC02665 (spiral)</td><td>13.92</td><td>13.12</td><td>12.97</td><td>12.79</td><td>13.92</td><td>13.12</td><td>12.97</td><td>12.79</td></tr><tr><td>WISEAJ031917_76+413839_6 (elliptical)</td><td>13.61</td><td>12.78</td><td>12.65</td><td>12.47</td><td>13.57</td><td>12.97</td><td>12.59</td><td>12.41</td></tr><tr><td>EDwC-0120 (dwarf)</td><td>18.88</td><td>18.35</td><td>18.26</td><td>18.23</td><td>18.85</td><td>17.97</td><td>17.52</td><td>17.81</td></tr></tbody></table>

**Notes.** Direct estimates of the uncertainties on magnitudes derived by Archangel and AutoProf are negligible, while the uncertainties derived by varying the sky background and fitting the growth curve are below 0.05 but for the dwarf galaxy. Magnitudes obtained with both software codes are very similar, if not equal, and differences are below a few percent. The difference in the NISP magnitudes for the dwarf galaxy can be explained by the different definitions of the radius, with the curves of growth being in very good agreement, as shown in Fig. B.3.

<figure><img src="image_35.png" /><figcaption>Fig. B.3: Surface-brightness profiles (red and orange lines, and left axis) and curves of growth (blue lines and right axis) obtained for three galaxies whose names are given at the top of each panel. The photometry has been performed with AutoProf (dashed lines) and Archangel (solid lines). There is a good agreement between both software codes.</figcaption></figure>
<table><caption>Table C.1: Parameters extracted from Tables C.3 to C.5, along with their descriptions and associated table numbers.</caption><thead><tr><th>Parameter</th><th>Description</th><th>Table numbers</th></tr></thead><tbody><tr><td>ID</td><td>Object identifier</td><td>Table C.3 to Table C.9</td></tr><tr><td>RA</td><td>Right ascension in degrees</td><td>Table C.3 to Table C.9</td></tr><tr><td>Dec</td><td>Declination in degrees</td><td>Table C.3 to Table C.9</td></tr><tr><td>x<sub>pix</sub></td><td>x-coordinate in pixels for AutoProf run</td><td>Table C.3</td></tr><tr><td>y<sub>pix</sub></td><td>y-coordinate in pixels for AutoProf run</td><td>Table C.3</td></tr><tr><td>I<sub>E</sub></td><td>Apparent magnitude in VIS band</td><td>Table C.3</td></tr><tr><td>M(I<sub>E</sub>)</td><td>Absolute magnitude in VIS band</td><td>Table C.3</td></tr><tr><td>R<sub>e,arcsec</sub></td><td>Effective radius in arcseconds</td><td>Table C.3</td></tr><tr><td>n</td><td>Sersic index</td><td>Table C.3</td></tr><tr><td>AR</td><td>Axis ratio</td><td>Table C.3</td></tr><tr><td>PA</td><td>Position angle in degrees</td><td>Table C.3</td></tr><tr><td>μ<sub>I<sub>E</sub>,0,GD</sub></td><td>Central surface brightness (Graham and Driver)</td><td>Table C.3</td></tr><tr><td>μ<sub>I<sub>E</sub>,e,GD</sub></td><td>Surface brightness at effective radius (Graham and Driver)</td><td>Table C.3</td></tr><tr><td>⟨μ<sub>I<sub>E</sub>,e,GD</sub>⟩</td><td>Average surface brightness at effective radius (Graham and Driver)</td><td>Table C.3</td></tr><tr><td>μ<sub>I<sub>E</sub>,0</sub></td><td>Central surface brightness</td><td>Table C.3</td></tr><tr><td>μ<sub>I<sub>E</sub>,e</sub></td><td>Surface brightness at effective radius</td><td>Table C.3</td></tr><tr><td>⟨μ<sub>I<sub>E</sub>,e</sub>⟩</td><td>Average surface brightness at effective radius</td><td>Table C.3</td></tr><tr><td>σ<sub>x</sub></td><td>Error on x-coordinate in pixels</td><td>Table C.4</td></tr><tr><td>σ<sub>y</sub></td><td>Error on y-coordinate in pixels</td><td>Table C.4</td></tr><tr><td>σ<sub>I<sub>E</sub></sub></td><td>Error on apparent magnitude</td><td>Table C.4</td></tr><tr><td>σ<sub>M(I<sub>E</sub>)</sub></td><td>Error on absolute magnitude</td><td>Table C.4</td></tr><tr><td>σ<sub>R<sub>e,arcsec</sub></sub></td><td>Error on effective radius in arcseconds</td><td>Table C.4</td></tr><tr><td>σ<sub>n</sub></td><td>Error on Sersic index</td><td>Table C.4</td></tr><tr><td>σ<sub>AR</sub></td><td>Error on axis ratio</td><td>Table C.4</td></tr><tr><td>σ<sub>PA</sub></td><td>Error on position angle in degrees</td><td>Table C.4</td></tr><tr><td>σ<sub>μ<sub>I<sub>E</sub>,0,GD</sub></sub></td><td>Error on central surface brightness (Graham and Driver)</td><td>Table C.4</td></tr><tr><td>σ<sub>μ<sub>I<sub>E</sub>,e,GD</sub></sub></td><td>Error on surface brightness at effective radius (Graham and Driver)</td><td>Table C.4</td></tr><tr><td>σ<sub>⟨μ<sub>I<sub>E</sub>,0,GD</sub>⟩</sub></td><td>Error on average surface brightness at effective radius (Graham and Driver)</td><td>Table C.4</td></tr><tr><td>σ<sub>μ<sub>I<sub>E</sub>,0</sub></sub></td><td>Error on central surface brightness</td><td>Table C.4</td></tr><tr><td>σ<sub>μ<sub>I<sub>E</sub>,e</sub></sub></td><td>Error on surface brightness at effective radius</td><td>Table C.4</td></tr><tr><td>σ<sub>⟨μ<sub>I<sub>E</sub>,e</sub>⟩</sub></td><td>Error on average surface brightness at effective radius</td><td>Table C.4</td></tr><tr><td>z<sub>spec</sub></td><td>Spectroscopic redshift from literature</td><td>Table C.5</td></tr><tr><td>z<sub>phot</sub></td><td>SDSS or NED Photometric redshift</td><td>Table C.5</td></tr><tr><td>σ<sub>z<sub>spec</sub></sub></td><td>Error on spectroscopic redshift</td><td>Table C.5</td></tr><tr><td>σ<sub>z<sub>phot</sub></sub></td><td>Error on photometric redshift</td><td>Table C.5</td></tr><tr><td>flagtool</td><td>Tool indicator (AP for AutoProf, APh for AstroPhot)</td><td>Table C.5</td></tr><tr><td>EC(I<sub>E</sub>)</td><td>VIS extinction correction c<sub>I<sub>E</sub></sub> E(B-V) from Eq. (1) to be used for all VIS magnitudes</td><td>Table C.5</td></tr><tr><td>EC(Y<sub>E</sub>)</td><td>Y extinction correction c<sub>Y<sub>E</sub></sub> E(B-V) from Eq. (1) to be used for all Y<sub>E</sub> magnitudes</td><td>Table C.5</td></tr><tr><td>EC(J<sub>E</sub>)</td><td>J extinction correction c<sub>J<sub>E</sub></sub> E(B-V) from Eq. (1) to be used for all J<sub>E</sub> magnitudes</td><td>Table C.5</td></tr><tr><td>EC(H<sub>E</sub>)</td><td>H extinction correction c<sub>H<sub>E</sub></sub> E(B-V) from Eq. (1) to be used for all H<sub>E</sub> magnitudes</td><td>Table C.5</td></tr><tr><td>σ<sub>EC(I<sub>E</sub>)</sub></td><td>Error on VIS extinction correction</td><td>Table C.5</td></tr><tr><td>σ<sub>EC(Y<sub>E</sub>)</sub></td><td>Error on Y<sub>E</sub> extinction correction</td><td>Table C.5</td></tr><tr><td>σ<sub>EC(J<sub>E</sub>)</sub></td><td>Error on J<sub>E</sub> extinction correction</td><td>Table C.5</td></tr><tr><td>σ<sub>EC(H<sub>E</sub>)</sub></td><td>Error on H<sub>E</sub> extinction correction</td><td>Table C.5</td></tr></tbody></table>
<table><caption>Table C.2: Parameters extracted from Tables C.6 to C.9, along with their descriptions and associated table numbers.</caption><thead><tr><th>Parameter</th><th>Description</th><th>Table numbers</th></tr></thead><tbody><tr><td>ID</td><td>Object identifier</td><td>Table C.6 to Table C.8</td></tr><tr><td>RA</td><td>Right Ascension in degrees</td><td>Table C.6 to Table C.8</td></tr><tr><td>Dec</td><td>Declination in degrees</td><td>Table C.6 to Table C.8</td></tr><tr><td>I<sub>E</sub></td><td>Magnitude within 1 R<sub>e</sub> aperture in the VIS band</td><td>Table C.6</td></tr><tr><td>M(I<sub>E</sub>)</td><td>Absolute magnitude within 1 R<sub>e</sub> aperture in the VIS band</td><td>Table C.6</td></tr><tr><td>Y<sub>E</sub></td><td>Magnitude within 1 R<sub>e</sub> aperture in the Y<sub>E</sub> band</td><td>Table C.6</td></tr><tr><td>M(Y<sub>E</sub>)</td><td>Absolute magnitude within 1 R<sub>e</sub> aperture in the Y<sub>E</sub> band</td><td>Table C.6</td></tr><tr><td>J<sub>E</sub></td><td>Magnitude within 1 R<sub>e</sub> aperture in the J<sub>E</sub> band</td><td>Table C.6</td></tr><tr><td>M(J<sub>E</sub>)</td><td>Absolute magnitude within 1 R<sub>e</sub> aperture in the J<sub>E</sub> band</td><td>Table C.6</td></tr><tr><td>H<sub>E</sub></td><td>Magnitude within 1 R<sub>e</sub> aperture in the H<sub>E</sub> band</td><td>Table C.6</td></tr><tr><td>M(H<sub>E</sub>)</td><td>Absolute magnitude within 1 R<sub>e</sub> aperture in the H<sub>E</sub> band</td><td>Table C.7</td></tr><tr><td>σI<sub>E</sub></td><td>Error on the magnitude within 1 R<sub>e</sub> aperture in the VIS band</td><td>Table C.7</td></tr><tr><td>σM(I<sub>E</sub>)</td><td>Error on the absolute magnitude within 1 R<sub>e</sub> aperture in the VIS band</td><td>Table C.7</td></tr><tr><td>σY<sub>E</sub></td><td>Error on the magnitude within 1 R<sub>e</sub> aperture in the Y<sub>E</sub> band</td><td>Table C.7</td></tr><tr><td>σM(I<sub>E</sub>)</td><td>Error on the absolute magnitude within 1 R<sub>e</sub> aperture in the Y<sub>E</sub> band</td><td>Table C.7</td></tr><tr><td>σJ<sub>E</sub></td><td>Error on the magnitude within 1 R<sub>e</sub> aperture in the J<sub>E</sub> band</td><td>Table C.7</td></tr><tr><td>σM(J<sub>E</sub>)</td><td>Error on the absolute magnitude within 1 R<sub>e</sub> aperture in the J<sub>E</sub> band</td><td>Table C.7</td></tr><tr><td>σH<sub>E</sub></td><td>Error on the magnitude within 1 R<sub>e</sub> aperture in the H<sub>E</sub> band</td><td>Table C.7</td></tr><tr><td>σM(H<sub>E</sub>)</td><td>Error on the absolute magnitude within 1 R<sub>e</sub> aperture in the H<sub>E</sub> band</td><td>Table C.7</td></tr><tr><td>I<sub>E</sub></td><td>Total forced magnitude in the VIS band</td><td>Table C.8</td></tr><tr><td>M(I<sub>E</sub>)</td><td>Total absolute forced magnitude in the VIS band</td><td>Table C.8</td></tr><tr><td>Y<sub>E</sub></td><td>Total forced magnitude in the Y<sub>E</sub> band</td><td>Table C.8</td></tr><tr><td>M(Y<sub>E</sub>)</td><td>Total absolute forced magnitude in the Y<sub>E</sub> band</td><td>Table C.8</td></tr><tr><td>J<sub>E</sub></td><td>Total forced magnitude in the J<sub>E</sub> band</td><td>Table C.8</td></tr><tr><td>M(J<sub>E</sub>)</td><td>Total absolute forced magnitude in the J<sub>E</sub> band</td><td>Table C.8</td></tr><tr><td>H<sub>E</sub></td><td>Total forced magnitude in the H<sub>E</sub> band</td><td>Table C.8</td></tr><tr><td>M(H<sub>E</sub>)</td><td>Total absolute forced magnitude in the H<sub>E</sub> band</td><td>Table C.8</td></tr><tr><td>σI<sub>E</sub></td><td>Error on the forced magnitude in the VIS band</td><td>Table C.9</td></tr><tr><td>σM(I<sub>E</sub>)</td><td>Error on the absolute forced magnitude in the VIS band</td><td>Table C.9</td></tr><tr><td>σI<sub>E</sub></td><td>Error on the forced magnitude in the Y<sub>E</sub> band</td><td>Table C.9</td></tr><tr><td>σM(Y<sub>E</sub>)</td><td>Error on the absolute forced magnitude in the Y<sub>E</sub> band</td><td>Table C.9</td></tr><tr><td>σJ<sub>E</sub></td><td>Error on the forced magnitude in the J<sub>E</sub> band</td><td>Table C.9</td></tr><tr><td>σM(J<sub>E</sub>)</td><td>Error on the absolute forced magnitude in the J<sub>E</sub> band</td><td>Table C.9</td></tr><tr><td>σH<sub>E</sub></td><td>Error on the forced magnitude in the H<sub>E</sub> band</td><td>Table C.9</td></tr><tr><td>σM(H<sub>E</sub>)</td><td>Error on the absolute forced magnitude in the H<sub>E</sub> band</td><td>Table C.9</td></tr></tbody></table>
<table><caption>Table C.3: Primary data from VIS photometry.</caption><thead><tr><th>ID</th><th>RA</th><th>Dec</th><th>x<sub>pix</sub></th><th>y<sub>pix</sub></th><th>I<sub>E</sub></th><th>M(I<sub>E</sub>)</th><th>R<sub>arcsec</sub></th><th>n</th><th>AR</th><th>PA</th><th>μ<sub>I_E,0</sub></th><th>μ<sub>I_E,0,GD</sub></th><th>μ<sub>I_E,e</sub></th><th>⟨μ<sub>I_E,e,GD</sub>⟩</th><th>μ<sub>I_E,0</sub></th><th>μ<sub>I_E,e</sub></th><th>⟨μ<sub>I_E,e</sub>⟩</th></tr></thead><tbody><tr><td>CGCG540-074</td><td>49.115</td><td>41.627</td><td>1001.880</td><td>1002.000</td><td>13.402</td><td>-20.885</td><td>9.649</td><td>3.273</td><td>0.744</td><td>29.697</td><td>16.781</td><td>25.108</td><td>23.715</td><td>15.540</td><td>21.357</td><td>16.711</td></tr><tr><td>WISEAJ031637_12+414721_3</td><td>49.155</td><td>41.789</td><td>2008.470</td><td>2009.570</td><td>15.110</td><td>-19.177</td><td>8.288</td><td>4.017</td><td>0.929</td><td>152.641</td><td>18.394</td><td>26.721</td><td>25.328</td><td>17.169</td><td>22.840</td><td>17.745</td></tr><tr><td>2MASXJ03165143+4127342</td><td>49.214</td><td>41.459</td><td>987.590</td><td>999.130</td><td>14.942</td><td>-19.345</td><td>14.854</td><td>2.817</td><td>0.754</td><td>76.206</td><td>19.162</td><td>27.489</td><td>26.096</td><td>18.518</td><td>23.503</td><td>18.619</td></tr><tr><td>GAIADR3239372962793322368</td><td>49.301</td><td>41.381</td><td>499.500</td><td>499.020</td><td>16.650</td><td>-17.637</td><td>3.525</td><td>4.880</td><td>0.560</td><td>17.690</td><td>26.020</td><td>24.620</td><td>17.080</td><td>22.090</td><td>18.060</td><td>...</td></tr><tr><td>7488</td><td>49.495</td><td>41.163</td><td>499.300</td><td>499.180</td><td>17.390</td><td>-16.897</td><td>4.234</td><td>1.280</td><td>0.480</td><td>158.050</td><td>26.840</td><td>25.440</td><td>19.870</td><td>22.630</td><td>20.590</td><td>...</td></tr></tbody></table>

<table><caption>Table C.4: Associated errors for the primary data catalogue.</caption><thead><tr><th>ID</th><th>RA</th><th>Dec</th><th>σ<sub>xpix</sub></th><th>σ<sub>ypix</sub></th><th>σ<sub>I_E</sub></th><th>σ<sub>M(I_E)</sub></th><th>σ<sub>R<sub>arcsec</sub></sub></th><th>σ<sub>n</sub></th><th>σ<sub>AR</sub></th><th>σ<sub>PA</sub></th><th>σ<sub>μ<sub>I_E,0</sub></sub></th><th>σ<sub>μ<sub>I_E,0,GD</sub></sub></th><th>σ<sub>μ<sub>I_E,e</sub></sub></th><th>σ<sub>μ<sub>I_E,e,GD</sub></sub></th><th>σ<sub>μ<sub>I_E,0</sub></sub></th><th>σ<sub>μ<sub>I_E,e</sub></sub></th><th>σ<sub>⟨μ<sub>I_E,e</sub>⟩</sub></th></tr></thead><tbody><tr><td>CGCG540-074</td><td>49.115</td><td>41.627</td><td>0.010</td><td>0.010</td><td>0.001</td><td>0.001</td><td>0.189</td><td>0.118</td><td>0.018</td><td>1.851</td><td>0.043</td><td>0.043</td><td>0.043</td><td>0.000</td><td>0.043</td><td>0.000</td></tr><tr><td>WISEAJ031637_12+414721_3</td><td>49.155</td><td>41.789</td><td>0.010</td><td>0.010</td><td>0.003</td><td>0.003</td><td>0.163</td><td>0.056</td><td>0.002</td><td>1.128</td><td>0.029</td><td>0.029</td><td>0.029</td><td>0.000</td><td>0.029</td><td>0.000</td></tr><tr><td>2MASXJ03165143+4127342</td><td>49.214</td><td>41.459</td><td>0.010</td><td>0.010</td><td>0.001</td><td>0.001</td><td>0.291</td><td>0.102</td><td>0.039</td><td>1.158</td><td>0.023</td><td>0.023</td><td>0.023</td><td>0.000</td><td>0.023</td><td>0.000</td></tr><tr><td>GAIADR3239372962793322368</td><td>49.301</td><td>41.381</td><td>0.010</td><td>0.010</td><td>0.000</td><td>0.000</td><td>0.069</td><td>0.150</td><td>0.040</td><td>0.280</td><td>0.030</td><td>0.030</td><td>0.030</td><td>0.000</td><td>0.030</td><td>0.000</td></tr><tr><td>7488</td><td>49.495</td><td>41.163</td><td>0.010</td><td>0.010</td><td>0.000</td><td>0.000</td><td>0.083</td><td>0.010</td><td>0.050</td><td>1.440</td><td>0.050</td><td>0.050</td><td>0.050</td><td>0.000</td><td>0.050</td><td>0.000</td></tr></tbody></table>
<table><caption>Table C.5: Redshift and extinction corrections.</caption><thead><tr><th>ID</th><th>RA</th><th>Dec</th><th>zspec</th><th>zphot</th><th>σ<sub>spec</sub></th><th>σ<sub>phot</sub></th><th>flagtool EC(I<sub>E</sub>) EC(Y<sub>E</sub>) EC(J<sub>E</sub>) EC(H<sub>E</sub>) σ<sub>EC(J<sub>E</sub>)</th><th>σ<sub>EC(Y<sub>E</sub>)</th><th>σ<sub>EC(J<sub>E</sub>)</th><th>σ<sub>EC(H<sub>E</sub>)</th></tr></thead><tbody><tr><td>CGCG540-074</td><td>49.115</td><td>41.627</td><td>0.017</td><td>0.024</td><td>0.000</td><td>0.007</td><td>AP</td><td>0.276</td><td>0.138</td><td>0.094</td><td>0.061</td><td>0.015</td><td>0.008</td><td>0.005</td><td>0.003</td></tr><tr><td>WISEAJ031637 12+414721_3</td><td>49.155</td><td>41.789</td><td>0.018</td><td>0.046</td><td>0.000</td><td>0.013</td><td>AP</td><td>0.302</td><td>0.152</td><td>0.103</td><td>0.067</td><td>0.016</td><td>0.008</td><td>0.006</td><td>0.004</td></tr><tr><td>2MASXJ03165143+4127342</td><td>49.214</td><td>41.459</td><td>-99.000</td><td>0.018</td><td>-99.000</td><td>0.049</td><td>AP</td><td>0.285</td><td>0.143</td><td>0.098</td><td>0.063</td><td>0.016</td><td>0.008</td><td>0.006</td><td>0.004</td></tr><tr><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td></tr><tr><td>GAIADR3239372962793322368</td><td>49.301</td><td>41.381</td><td>-99.990</td><td>-99.990</td><td>-99.990</td><td>-99.990</td><td>AP</td><td>0.309</td><td>0.155</td><td>0.106</td><td>0.069</td><td>0.018</td><td>0.009</td><td>0.006</td><td>0.004</td></tr><tr><td>7488</td><td>49.495</td><td>41.163</td><td>-99.990</td><td>-99.990</td><td>-99.990</td><td>-99.990</td><td>AP</td><td>0.406</td><td>0.204</td><td>0.139</td><td>0.090</td><td>0.025</td><td>0.013</td><td>0.009</td><td>0.006</td></tr></tbody></table>

<table><caption>Table C.6: Magnitudes within 1 effective radius in VIS and NISP bands.</caption><thead><tr><th>ID</th><th>RA</th><th>Dec</th><th>I<sub>E</sub></th><th>M(I<sub>E</sub>)</th><th>Y<sub>E</sub></th><th>M(Y<sub>E</sub>)</th><th>J<sub>E</sub></th><th>M(J<sub>E</sub>)</th><th>H<sub>E</sub></th><th>M(H<sub>E</sub>)</th></tr></thead><tbody><tr><td>CGCG540-074</td><td>49.115</td><td>41.627</td><td>14.119</td><td>-20.168</td><td>13.346</td><td>-20.941</td><td>13.174</td><td>-21.112</td><td>13.035</td><td>-21.252</td></tr><tr><td>WISEAJ031637_12+414721_3</td><td>49.155</td><td>41.789</td><td>15.827</td><td>-18.460</td><td>15.039</td><td>-19.248</td><td>14.885</td><td>-19.402</td><td>14.740</td><td>-19.547</td></tr><tr><td>2MASXJ03165143+4127342</td><td>49.214</td><td>41.459</td><td>15.667</td><td>-18.620</td><td>15.029</td><td>-19.257</td><td>14.903</td><td>-19.383</td><td>14.776</td><td>-19.510</td></tr><tr><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td></tr><tr><td>GAIADR3239372962793322368</td><td>49.301</td><td>41.381</td><td>17.370</td><td>-16.917</td><td>16.546</td><td>-17.741</td><td>16.399</td><td>-17.888</td><td>16.189</td><td>-18.098</td></tr><tr><td>7488</td><td>49.495</td><td>41.163</td><td>18.100</td><td>-16.187</td><td>17.464</td><td>-16.822</td><td>17.383</td><td>-16.904</td><td>17.266</td><td>-17.021</td></tr></tbody></table>

<table><caption>Table C.7: Associated errors of the 1R<sub>c</sub> magnitudes catalogue.</caption><thead><tr><th>ID</th><th>RA</th><th>Dec</th><th>σ<sub>I<sub>E</sub></sub></th><th>σ<sub>M(I<sub>E</sub>)</sub></th><th>σ<sub>Y<sub>E</sub></sub></th><th>σ<sub>M(Y<sub>E</sub>)</sub></th><th>σ<sub>J<sub>E</sub></sub></th><th>σ<sub>M(J<sub>E</sub>)</sub></th><th>σ<sub>H<sub>E</sub></sub></th><th>σ<sub>M(H<sub>E</sub>)</sub></th></tr></thead><tbody><tr><td>CGCG540-074</td><td>49.115</td><td>41.627</td><td>0.001</td><td>0.001</td><td>0.002</td><td>0.002</td><td>0.001</td><td>0.001</td><td>0.002</td><td>0.002</td></tr><tr><td>WISEAJ031637_12+414721_3</td><td>49.155</td><td>41.789</td><td>0.013</td><td>0.013</td><td>0.004</td><td>0.004</td><td>0.004</td><td>0.004</td><td>0.004</td><td>0.004</td></tr><tr><td>2MASXJ03165143+4127342</td><td>49.214</td><td>41.459</td><td>0.015</td><td>0.015</td><td>0.001</td><td>0.001</td><td>0.001</td><td>0.001</td><td>0.001</td><td>0.001</td></tr><tr><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td></tr><tr><td>GAIADR3239372962793322368</td><td>49.301</td><td>41.381</td><td>0.010</td><td>0.010</td><td>0.005</td><td>0.005</td><td>0.006</td><td>0.005</td><td>0.004</td><td>0.004</td></tr><tr><td>7488</td><td>49.495</td><td>41.163</td><td>0.020</td><td>0.020</td><td>0.001</td><td>0.001</td><td>0.001</td><td>0.001</td><td>0.001</td><td>0.001</td></tr></tbody></table>
<table><caption>Table C.8: Magnitudes using VIS photometry to constrain NISP photometry.</caption><thead><tr><th>ID</th><th>RA</th><th>Dec</th><th>I<sub>E</sub></th><th>M(I<sub>E</sub>)</th><th>Y<sub>E</sub></th><th>M(Y<sub>E</sub>)</th><th>J<sub>E</sub></th><th>M(J<sub>E</sub>)</th><th>H<sub>E</sub></th><th>M(H<sub>E</sub>)</th></tr></thead><tbody><tr><td>CGCG540-074</td><td>49.115</td><td>41.627</td><td>13.402</td><td>-20.885</td><td>12.952</td><td>-21.335</td><td>12.447</td><td>-21.839</td><td>12.300</td><td>-21.986</td></tr><tr><td>WISEAJ031637_12+414721_3</td><td>49.155</td><td>41.789</td><td>15.110</td><td>-19.177</td><td>14.529</td><td>-19.758</td><td>14.277</td><td>-20.009</td><td>14.112</td><td>-20.174</td></tr><tr><td>2MASXJ03165143+4127342</td><td>49.214</td><td>41.459</td><td>14.942</td><td>-19.345</td><td>14.354</td><td>-19.933</td><td>14.234</td><td>-20.053</td><td>14.066</td><td>-20.221</td></tr><tr><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td></tr><tr><td>GAIADR3239372962793322368</td><td>49.301</td><td>41.381</td><td>16.650</td><td>-17.637</td><td>15.948</td><td>-18.339</td><td>15.776</td><td>-18.511</td><td>15.602</td><td>-18.685</td></tr><tr><td>7488</td><td>49.495</td><td>41.163</td><td>17.390</td><td>-16.897</td><td>16.812</td><td>-17.474</td><td>16.747</td><td>-17.540</td><td>16.628</td><td>-17.659</td></tr></tbody></table>

<table><caption>Table C.9: Associated errors of the forced magnitudes.</caption><thead><tr><th>ID</th><th>RA</th><th>Dec</th><th>σ<sub>E</sub></th><th>σ<sub>M(I<sub>E</sub>)</sub></th><th>σ<sub>Y<sub>E</sub></sub></th><th>σ<sub>M(Y<sub>E</sub>)</sub></th><th>σ<sub>J<sub>E</sub></sub></th><th>σ<sub>M(J<sub>E</sub>)</sub></th><th>σ<sub>H<sub>E</sub></sub></th><th>σ<sub>M(H<sub>E</sub>)</sub></th></tr></thead><tbody><tr><td>CGCG540-074</td><td>49.115</td><td>41.627</td><td>0.001</td><td>0.001</td><td>0.002</td><td>0.002</td><td>0.001</td><td>0.001</td><td>0.002</td><td>0.002</td></tr><tr><td>WISEAJ031637_12+414721_3</td><td>49.155</td><td>41.789</td><td>0.003</td><td>0.003</td><td>0.003</td><td>0.003</td><td>0.003</td><td>0.003</td><td>0.003</td><td>0.003</td></tr><tr><td>2MASXJ03165143+4127342</td><td>49.214</td><td>41.459</td><td>0.001</td><td>0.001</td><td>0.002</td><td>0.002</td><td>0.002</td><td>0.002</td><td>0.002</td><td>0.002</td></tr><tr><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td></tr><tr><td>GAIADR3239372962793322368</td><td>49.301</td><td>41.381</td><td>0.000</td><td>0.000</td><td>0.004</td><td>0.004</td><td>0.004</td><td>0.004</td><td>0.003</td><td>0.003</td></tr><tr><td>7488</td><td>49.495</td><td>41.163</td><td>0.000</td><td>0.000</td><td>0.002</td><td>0.002</td><td>0.001</td><td>0.001</td><td>0.001</td><td>0.001</td></tr></tbody></table>
## Appendix D: SourceExtractor parameters

We report in Table D.1 the main parameters of SourceExtractor on the CFHT *i* band. Similar files for the NISP and VIS bands are available with the public distribution of the catalogues.<fnref n="17" /> The list of output parameters is provided in the appendix of Cuillandre et al. (2025).

<table><caption>Table D.1: SourceExtractor input configuration for the CFHT *i* band.</caption><thead><tr><th></th><th></th><th></th></tr></thead><tbody><tr><td colspan="3">Catalogue</td></tr><tr><td>CATALOG_NAME</td><td>CFHT-MegaCam-i-Perseus-EROFOV-Flattened.v7.NISPdet.cat</td><td># name of the output catalogue</td></tr><tr><td>CATALOG_TYPE</td><td>ASCII_HEAD</td><td># NONE, ASCII, ASCII_HEAD, ASCII_SKYCAT, ASCII_VOTABLE, FITS_1.0 or FITS_LDAC</td></tr><tr><td>PARAMETERS_NAME</td><td>Config/ERO.PSF.param</td><td># name of the file containing catalogue contents</td></tr><tr><td colspan="3">Extraction</td></tr><tr><td>DETECT_TYPE</td><td>CCD</td><td># CCD (linear) or PHOTO (with gamma correction)</td></tr><tr><td>DETECT_MINAREA</td><td>5</td><td># min. # of pixels above threshold</td></tr><tr><td>DETECT_THRESHOLD</td><td>1.5</td><td># &lt;signmas&gt; or &lt;threshold&gt;, &lt;ZP&gt; in mag.arcsec-2</td></tr><tr><td>ANALYSIS_THRESHOLD</td><td>1.5</td><td># &lt;signmas&gt; or &lt;threshold&gt;, &lt;ZP&gt; in mag.arcsec-2</td></tr><tr><td>FILTER</td><td>Y</td><td># apply filter for detection (Y or N)?</td></tr><tr><td>FILTER_NAME</td><td>Config/gauss_1.5_3x3erbConv</td><td># name of the file containing the filter</td></tr><tr><td>DEBLEND_NTHRESH</td><td>64</td><td># Number of deblending sub-thresholds</td></tr><tr><td>DEBLEND_MINCONT</td><td>0.0001</td><td># Minimum contrast parameter for deblending</td></tr><tr><td>CLEAN</td><td>Y</td><td># Clean spurious detections? (Y or N)?</td></tr><tr><td>CLEAN_PARAM</td><td>1.0</td><td># Cleaning efficiency</td></tr><tr><td colspan="3">WEIGHTing</td></tr><tr><td>WEIGHT_TYPE</td><td>NONE,MAP_WEIGHT</td><td># type of WEIGHTing: NONE, BACKGROUND, MAP_RMS, MAP_VAR or MAP_WEIGHT</td></tr><tr><td>RESCALE_WEIGHTS</td><td>N</td><td># Rescale input weights/variances (Y/N)?</td></tr><tr><td>WEIGHT_IMAGE</td><td>NONE,CFHT-MegaCam-i-Perseus-EROFOV-Flattened.v7.weight.fits</td><td># weight-map filename</td></tr><tr><td colspan="3">Photometry</td></tr><tr><td>PHOT_APERTURES</td><td>4.2,6.7,1,2,4,8,16,32,19.5,26.7</td><td># MAG_APER aperture diameter(s) in pixels<br/># 1st and 2nd are COG related (2" diam + opt aper),<br/># last two are DES related = 5.8437" + 8"</td></tr><tr><td>PHOT_AUTOPARAMS</td><td>2.5, 3.5</td><td># MAG_AUTO parameters: &lt;Kron_fact&gt;, &lt;min radius&gt;</td></tr><tr><td>PHOT_PETROPARAMS</td><td>2.0, 3.5</td><td># MAG_PETRO parameters: &lt;Petrosian_fact&gt;, &lt;min radius&gt;</td></tr><tr><td>PHOT_AUTOAPERS</td><td>0.0,0.0</td><td># &lt;estimation&gt;, &lt;measurement&gt; minimum apertures<br/># for MAG_AUTO and MAG_PETRO</td></tr><tr><td>SATUR_KEY</td><td>SATURATE</td><td># keyword for saturation level (in ADUs)</td></tr><tr><td>MAG_ZEROPOINT</td><td>30.000</td><td># magnitude zero-point</td></tr><tr><td>MAG_GAMMA</td><td>4.0</td><td># gamma of emulsion (for photographic scans)</td></tr><tr><td>WEIGHT_GAIN</td><td>Y</td><td># modulate gain (E/ADU) with weights? (Y/N)</td></tr><tr><td>GAIN_KEY</td><td>GAIN</td><td># keyword for detector gain in e-/ADU</td></tr><tr><td>PIXEL_SCALE</td><td>0.3</td><td># size of pixel in arcsec (0=use FITS WCS info)</td></tr><tr><td colspan="3">Star/Galaxy Separation</td></tr><tr><td>SEEING_FWHM</td><td>0.56</td><td># stellar FWHM in arcsec</td></tr><tr><td>STARNW_NAME</td><td>Config/default.nnw</td><td># Neural-Network_Weight table filename</td></tr><tr><td colspan="3">Background</td></tr><tr><td>BACK_TYPE</td><td>AUTO</td><td># AUTO or MANUAL</td></tr><tr><td>BACK_VALUE</td><td>0.0</td><td># Default background value in MANUAL mode</td></tr><tr><td>BACK_SIZE</td><td>22</td><td># Background mesh: &lt;size&gt; or &lt;width&gt;, &lt;height&gt;</td></tr><tr><td>BACK_FILTERSIZE</td><td>3</td><td># Background filter: &lt;size&gt; or &lt;width&gt;, &lt;height&gt;</td></tr><tr><td colspan="3">Check Image</td></tr><tr><td>CHECKIMAGE_TYPE</td><td>SEGMENTATION</td><td># can be NONE, BACKGROUND, BACKGROUND_RMS, MINIBACKGROUND, MINIBACK_RMS, -BACKGROUND, FILTERED, OBJECTS, -OBJECTS, SEGMENTATION, or APERTURES</td></tr><tr><td>CHECKIMAGE_NAME</td><td>CFHT-MegaCam-i-Perseus-EROFOV-Flattened.v7.NISPdet.segmentation.fits</td><td># Filename for the check-image</td></tr><tr><td colspan="3">Memory (change with caution!)</td></tr></tbody></table>

<footnote n="17">¹⁷ Euclid Early Release Observations (2024).</footnote>
<table><caption>Table D.1: Continued.</caption><tr><td>MEMORY OBJSTACK</td><td>50000</td><td># number of objects in stack</td></tr><tr><td>MEMORY PIXSTACK</td><td>3000000</td><td># number of pixels in stack</td></tr><tr><td>MEMORY BUFSIZE</td><td>8092</td><td># number of lines in buffer</td></tr><tr><td colspan="3">ASSOCiation</td></tr><tr><td>ASSOC_NAME</td><td>sky.list</td><td># name of the ASCII file to ASSOCiate</td></tr><tr><td>ASSOC_DATA</td><td>2,3,4</td><td># columns of the data to replicate (0=all)</td></tr><tr><td>ASSOC_PARAMS</td><td>2,3,4</td><td># columns of xpos,ypos[,mag]</td></tr><tr><td>ASSOC'RADIUS</td><td>2.0</td><td># cross-matching radius (pixels)</td></tr><tr><td>ASSOC_TYPE</td><td>NEAREST</td><td># ASSOCiation method: FIRST, NEAREST, MEAN, MAG_MEAN, SUM, MAG_SUM, MIN or MAX</td></tr><tr><td>ASSOCSELEC_TYPE</td><td>MATCHED</td><td># ASSOC selection type: ALL, MATCHED or -MATCHED</td></tr></table>