Exploring the Brighter-fatter Effect with the Hyper Suprime-Cam

• Published in: The Astronomical journal Vol. 155; no. 6; pp. 258 - 268
• Main Authors: Coulton, William R., Armstrong, Robert, Smith, Kendrick M., Lupton, Robert H., Spergel, David N.
• Format: Journal Article
• Language: English
• Published: Madison The American Astronomical Society 01.06.2018; IOP Publishing
• Subjects: Astronomy; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CORRELATIONS; ELECTRIC FIELDS; First principles; IMAGE PROCESSING; instrumentation: detectors; Kernels; LUMINOSITY; Pixels; Point spread functions; STARS; techniques: image processing
• ISSN: 0004-6256; 1538-3881; 1538-3881
• DOI: 10.3847/1538-3881/aac08d

The brighter-fatter effect has been postulated to arise due to the build up of a transverse electric field, produced as photocharges accumulate in the pixels' potential wells. We investigate the brighter-fatter effect in the Hyper Suprime-Cam by examining flat fields and moments of stars. We observe deviations from the expected linear relation in the photon transfer curve (PTC), luminosity-dependent correlations between pixels in flat-field images, and a luminosity-dependent point-spread function (PSF) in stellar observations. Under the key assumptions of translation invariance and Maxwell's equations in the quasi-static limit, we give a first-principles proof that the effect can be parameterized by a translationally invariant scalar kernel. We describe how this kernel can be estimated from flat fields and discuss how this kernel has been used to remove the brighter-fatter distortions in Hyper Suprime-Cam images. We find that our correction restores the expected linear relation in the PTCs and significantly reduces, but does not completely remove, the luminosity dependence of the PSF over a wide range of magnitudes.