Brighter-fatter Effect in Near-infrared Detectors. II. Autocorrelation Analysis of H4RG-10 Flats

Abstract

The Wide Field Infrared Survey Telescope (WFIRST) will investigate the origins of cosmic acceleration using weak gravitational lensing at near-infrared wavelengths. Lensing analyses place strict constraints on the precision of size and ellipticity measurements of the point-spread function. WFIRST will use infrared detector arrays, which must be fully characterized to inform data reduction and calibration procedures such that unbiased cosmological results can be achieved. Hirata & Choi introduces formalism to connect the cross-correlation signal of different flat field time samples to nonlinear detector behaviors such as the brighter fatter effect (BFE) and nonlinear inter-pixel capacitance (NL-IPC), and this paper applies that framework to a WFIRST development detector, SCA 18237. We find a residual correlation signal after accounting for classical nonlinearity. This residual correlation contains a combination of the BFE and NL-IPC; however, further tests suggest that the BFE is the dominant mechanism. If interpreted as a pure BFE, it suggests that the effective area of a pixel is increased by (2.87 ± 0.03) × 10−7 (stat.) for every electron in the 4 nearest neighbors, with a rapid ∼r−5.6±0.2 fall-off of the effect for more distant neighbors. We show that the IPC inferred from hot pixels contains the same large-scale spatial variations as the IPC inferred from auto-correlations, albeit with an overall offset of ∼0.06%. The NL-IPC inferred from hot pixels is too small to explain the cross-correlation measurement, further supporting the BFE hypothesis. This work presents the first evidence for the BFE in an H4RG-10 detector, demonstrates some of the useful insights that can be gleaned from flat field statistics, and represents a significant step toward calibration of WFIRST data.