重新审视综合孔径成像中常用反卷积方法引起的通量恢复系统误差
Revisiting a flux recovery systematic error arising from common deconvolution methods used in aperture-synthesis imaging
AI总结：
本文重新审视了综合孔径成像中CLEAN类反卷积算法因图像单位不匹配导致的通量密度系统性偏移问题，通过模拟量化了误差范围并提出了可将误差降至百分之几的缓解方法。
摘要：
点扩展函数（PSF）是任何天文仪器的基本属性。在干涉仪中，不同的阵列配置结合其$uv$覆盖以及各种加权方案，会产生不规则但确定性的PSF。因此，通常使用CLEAN类算法对PSF进行反卷积以提高图像保真度。本文重新审视了一个显著效应，该效应导致任何干涉仪测量的通量密度都与真实值存在系统性偏移。使用一套精心控制的模拟，我们表明这种系统性偏移源于这些CLEAN类算法生成的图像在单位上的不匹配。我们说明这种系统误差可能很显著，范围从百分之几到百分之几十。考虑这一效应对于当前和未来的干涉阵列（如MeerKAT、LOFAR和SKA）非常重要，因为它们核心主导的配置自然会导致不规则的PSF。我们表明这种偏移独立于其他系统误差，并且可能因某些因素而恶化，例如对PSF的拟合优度、反卷积深度以及源的信噪比。最后，我们提出了几种能将此效应降低至仅百分之几的方法。
英文摘要：
The point-spread function (PSF) is a fundamental property of any astronomical instrument. In interferometers, differing array configurations combined with their $uv$ coverage, and various weighting schemes can produce an irregular but deterministic PSF. As a result, the PSF is often deconvolved using CLEAN-style algorithms to improve image fidelity. In this paper, we revisit a significant effect that causes the flux densities measured with any interferometer to be systematically offset from the true values. Using a suite of carefully controlled simulations, we show that the systematic offset originates from a mismatch in the units of the image produced by these CLEAN-style algorithms. We illustrate that this systematic error can be significant, ranging from a few to tens of per cent. Accounting for this effect is important for current and future interferometric arrays, such as MeerKAT, LOFAR and the SKA, whose core-dominated configuration naturally causes an irregular PSF. We show that this offset is independent of other systematics, and can worsen due to some factors such as the goodness of the fit to the PSF, the deconvolution depth, and the signal-to-noise of the source. Finally, we present several methods that can reduce this effect to just a few per cent.
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