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## Fake Galaxies Generation   The fake galaxy models are generated by the **Sersic** function in GalSim package. The procedures can be summarized into following steps:   1. Input magnitude is converted into flux using calibrations extracted from HSC pipeline; and the input effective radius is converted into pixel unit (reff_pix). (reff\_pix).  2. Using input flux and reff\_pix, a GalSim.Sersic object is generated with its flux truncated at 10 times of the reff\_pix. Even when the Sersic index is high, the output image can still have a reasonable size without losing much flux at outer radii. 3. Using input axis ratio (b/a), simple q=b/a shear has been applied to the Sersic object to turn it into an elliptical model. Since GalSim perserve the total area, the real major-axis half-light radii of the output model becomes reff_pix reff\_pix  / sqrt(b/a). 4. Using input position angle (PA), the elliptical Sersic object is rotated. 5. PSF convolution is applied to the model using the PSF image extracted from HSC data products at the desired location. 6. An output image of the models is generated using the GalSim DrawImage function. ## Fake Galaxies Injection