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arXiv 1002.1479astro-ph.IMastro-ph.CO
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电荷转移无效率(CTI)对星系形状测量的影响

The effects of charge transfer inefficiency (CTI) on galaxy shape measurements

Jason Rhodes, Alexie Leauthaud, Chris Stoughton, Richard Massey, Kyle Dawson, William Kolbe, Natalie Roe

摘要:

我们研究了电荷转移效率(CTI)的影响,在CCD读出星系形状测量所需的弱引力透镜的研究。我们模拟了CCD读出与CTI,如带电粒子辐射损伤所造成的。我们验证我们的模拟实验室辐照CCD的数据。只有电荷陷阱的时间常数相同的顺序,在读出过程中的行传输之间的时间影响星系的形状测量。我们描述了CTI对不同星系种群的影响。我们的基线我们的研究围绕p沟道CCD已被证明具有电荷转移效率高达一个数量级优于几个型号的n沟道CCD设计用于空间应用。我们预测,对于距离读出寄存器最远的星系,星系形状测量的偏差Delta(e)将以每年2.65 +/- 0.02 x 10^(-4)的速度在L2处增加,以获得整个太阳周期的平均累积辐射照射。如果不进行校正,这将在大约4年内消耗暗能量任务的整个形状测量误差预算。其他地方展示的软件缓解技术可以将其降低约10倍,使其效果远低于任务要求。具有比我们研究的更高CTI的CCD可能无法满足未来暗能量任务的要求。我们将讨论如何设计硬件,以进一步减少CTI的影响。

英文摘要:

(Abridged) We examine the effects of charge transfer inefficiency (CTI) during CCD readout on galaxy shape measurements required by studies of weak gravitational lensing. We simulate a CCD readout with CTI such as that caused by charged particle radiation damage. We verify our simulations on data from laboratory-irradiated CCDs. Only charge traps with time constants of the same order as the time between row transfers during readout affect galaxy shape measurements. We characterize the effects of CTI on various galaxy populations. We baseline our study around p-channel CCDs that have been shown to have charge transfer efficiency up to an order of magnitude better than several models of n-channel CCDs designed for space applications. We predict that for galaxies furthest from the readout registers, bias in the measurement of galaxy shapes, Delta(e), will increase at a rate of 2.65 +/- 0.02 x 10^(-4) per year at L2 for accumulated radiation exposure averaged over the solar cycle. If uncorrected, this will consume the entire shape measurement error budget of a dark energy mission within about 4 years. Software mitigation techniques demonstrated elsewhere can reduce this by a factor of ~10, bringing the effect well below mission requirements. CCDs with higher CTI than the ones we studeied may not meet the requirements of future dark energy missions. We discuss ways in which hardware could be designed to further minimize the impact of CTI.

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