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Table 3.

Parameter distributions of the two types of simulations used to generate the training data for each GREAT3 subfield.

Branch type: Ground-based
Space-based
Training set to learn the prediction of: Point estimate Weight Point estimate Weight
Simulation type: Uniform Mock Uniform Mock
Shear components g1, g2 0 𝒰(−0.1, 0.1) 0 𝒰(−0.1, 0.1)
Galaxy ellipticity modulus εtrue ℛ(0.2)[0,0.7] ℛ(0.2)[0,0.7] ℛ(0.2)[0,0.7] ℛ(0.2)[0,0.7]
Sérsic indexan 𝒰(0.5, 4) 𝒰(0.5, 2.5) 𝒰(0.5, 4) 𝒰(0.5, 4)
Flux F (counts) 𝒰(10, 100) 𝒩(15, 20)[10,200] 𝒰(10, 100) 𝒩(0, 30)[10, 200]
Half-light radius R (pix) 𝒰(0.75, 3.0) 𝒩(1.0, 0.8)[0.75, 3.0] 𝒰(1.25, 10.0) 𝒩(2.5, 3.5)[1.25, 10.0]

Notes.

We use 𝒰(a, b) to denote the uniform distribution between a and b, 𝒩(μ, σ) to denote a normal distribution with mean μ and variance σ2, and ℛ(σ) for a Rayleigh distribution with mode σ. Intervals in subscript denote the range to which we clip a distribution, so that no sample falls outside of the given interval.

(a)

In practice, we grid the values for the Sérsic index instead of drawing them randomly. This significantly speeds up the galaxy stamp generation, as GalSim can reuse cached Sérsic profiles.

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