Open Access

Table A.1.

Model parameter priors used, with some values rounded.

Object Component Parameter Distribution Initial Position Step Size ([1σ])
θE, PEMD N(0.879, 0.133) 0.879 0.133
Mass:
PEMD
γPEMD U(1.5, 2.5) 1.95 0.02
(e1, e2) N(0, 0.2) (-0.047, 0.107) 0.2
(x, y) U(−3, 3) (-0.031, 0.021) 0.003

Main Deflector (D)
z = 0.6575
Rsersic U(0.001, 5) 0.296 0.01
Light:
Bulge Sérsic
nsersic Fixed 4
(e1, e2) U(−0.2, 0.2) (-0.048, 0.089) 0.1
(x, y) U(−1, 1) (-0.009, 0.009) 0.003

Light:
Disk Sérsic
Rsersic U(0.001, 5) 1.752 0.05
nsersic Fixed 1
(e1, e2) U(−0.5, 0.5) (-0.164, 0.154) 0.1
(x, y) Joined with Bulge Sérsic

γext, 1 U(−0.5, 0.5) 0.109 0.1
External Shear
z = 0.6575
Mass:
Shear
γext, 2 U(−0.5, 0.5) 0.025 0.1
(x, y) Fixed 0

Mass:
SIS
θE, X U(0.0001, 0.25) 0.15 0.01
Satellite (X)
z = 0.6575
γext, 2 U(−0.5, 0.5) 0.025 0.1
(x, y) Joined with Light

Rsersic U(0.0001, 0.1) 0.044 0.01
Light:
Sérsic
nsersic U(1, 10) 2 0.2
(e1, e2) Fixed (0.015, 0.018)
(x, y) U(Initial ± 0.07) (0.228, 2.046) 0.003

Mass:
SIS
θE, G2 N(0.622, 0.062) 0.622 0.1
(x, y) Joined with Light

Galaxy G2
z = 0.7450
Light:
Sérsic
Rsersic U(0.001, 5) 1 0.05
nsersic U(0.1, 2) 0.5 0.1
(e1, e2) Fixed (0, 0)
(x, y) Fixed (-3.998, -0.034)

Galaxy G3 Mass: θE, G3 N(0.088, 0.048)
z = 0.6575 SIS (x, y) Fixed (2.823, 7.006)

Galaxy G7 Mass: θE, G7 N(0.388, 0.030)
z = 0.6575 SIS (x, y) Fixed (-4.578, -11.719)

Free Flexion Mass: (g1, g2, g3, g4) U(−0.1, 0.1) 0 0.01
z = 0.6575 Flexion (x, y) Fixed (0, 0)

A1(x, y) U(Initial ± 0.3) (-0.760, 0.958) 0.007
Quasar Images
z = 0.6575
Light:
Point Sources
A2(x, y) U(Initial ± 0.3) (-0.050, 1.076) 0.007
B(x, y) U(Initial ± 0.3) (1.434, -0.302) 0.007
C(x, y) U(Initial ± 0.3) (-0.686, -0.579) 0.007

Rsersic U(0.04, 0.3) 0.2 0.01
Light:
Sérsic
nsersic U(0.15, 4) 1 0.25
(e1, e2) U(−0.15, 0.15) (0, 0) 0.03
Quasar Host Galaxy
z = 1.662
(x, y) U(Initial ± 1) (-0.45, 0.1) 0.03

Light: β U(0.031, 0.3) 0.031 0.025
Shapelets nmax Fixed {18, 20, 22} 0.1
(x, y) Joined with Sérsic

Notes. Parameters grouped by components (Deflector, Sérsic 1, Shapelets) with their corresponding types (Mass or Light). The bounds are represented as uniform distributions, with initial guesses and sampling step sizes ([σ]).

While the Einstein radii are given priors, their actual values are scaled with G2. This ensures the constraints provided by their observed velocity dispersions are passed to the models, while also minimizing the degeneracies between their parameters.

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