用Ia型超新星的透镜放大率诊断倍增误差
Diagnosing multiplicative error by lensing magnification of type Ia supernovae
摘要：
弱透镜效应导致Ia型超新星（SNe Ia）流量的空间相干波动。这种透镜放大率允许独立于宇宙剪切的弱透镜测量。它没有与宇宙剪切相关的形状测量误差，因此可以用于诊断和校准乘法误差。虽然这种透镜放大率很难在自相关中精确测量，但它与宇宙切变和重叠区域星系分布的交叉相关可以测量到更高的精度。因此，这些互相关可以对乘性误差施加有效的约束，并且在弱透镜场中所得到的约束是不受宇宙方差影响的。我们提出了两种方法实现这一想法，并估计其性能。我们发现，利用LSST望远镜（Zhan et al. 2008）的D2k巡天可以实现的$\sim 1$百万SNe Ia，可以检测到源星系在$z_s\sim 1$的$\sim 0.5\%$的乘法误差，并且可以将较大的乘法误差校正到$0.5\%$的水平。因此，这是一个很有希望的方法，可以控制第四阶段项目所需的百分之几的乘数。这两种方法的结合甚至有可能诊断和校准星系内禀排列，这是宇宙剪切宇宙学中的另一个主要系统误差。
英文摘要：
Weak lensing causes spatially coherent fluctuations in flux of type Ia supernovae (SNe Ia). This lensing magnification allows for weak lensing measurement independent of cosmic shear. It is free of shape measurement errors associated with cosmic shear and can therefore be used to diagnose and calibrate multiplicative error. Although this lensing magnification is difficult to measure accurately in auto correlation, its cross correlation with cosmic shear and galaxy distribution in overlapping area can be measured to significantly higher accuracy. Therefore these cross correlations can put useful constraint on multiplicative error, and the obtained constraint is free of cosmic variance in weak lensing field. We present two methods implementing this idea and estimate their performances. We find that, with $\sim 1$ million SNe Ia that can be achieved by the proposed D2k survey with the LSST telescope (Zhan et al. 2008), multiplicative error of $\sim 0.5\%$ for source galaxies at $z_s\sim 1$ can be detected and larger multiplicative error can be corrected to the level of $0.5\%$. It is therefore a promising approach to control the multiplicative to the sub-percent level required for stage IV projects. The combination of the two methods even has the potential to diagnose and calibrate galaxy intrinsic alignment, which is another major systematic error in cosmic shear cosmology.
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