The importance of magnification effects in galaxy-galaxy lensing
The importance of magnification effects in galaxy-galaxy lensing
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星系-星系透镜效应中放大效应的重要性
DOI：
10.1051/0004-6361/201936915
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发表时间：
2020
影响因子：
6.5
通讯作者：
Corella Puertas
中科院分区：
文献类型：
--
作者：
Schneider;Hilbert;Martin;Corella Puertas
放大率改变了观测到的天空中星系的局部数密度。这使星系周围的切向剪切剖面产生偏差：所谓的星系-星系透镜（GGL）信号。物理量的推断，如星系周围晕的平均质量分布，相应地受到放大效应的影响。我们使用Millennium Simulation的模拟剪切和星系数据来量化放大透镜和源数量计数对剪切和质量估计的影响。前者是由于大规模的物质分布在前景的透镜;后者是由于放大的源人口的物质与透镜。GGL信号通过有效的快速傅立叶变换从模拟中计算，该快速傅立叶变换也可以应用于真实的数据。的数值处理是补充的放大效应，这被证明是适合数值剪切数据的一个领先的顺序的分析描述。我们发现，放大效应是最强的陡峭的星系光度函数和高红移。对于一个KiDS+维京海盗+GAMA类巡天，其中透镜星系的红移tzd = 0.36，源星系在最后三个红移箱中，平均红移为，放大率校正改变剪切轮廓高达2%，质量偏差高达8%。 我们进一步考虑了一个更高的红移基准透镜样品，在zd = 0.83，在ther-band和源红移zs = 0.99的一个有限的幅度为22等。 通过这一点，我们发现，放大率校正改变剪切轮廓高达45%，质量偏差高达55%。正如预期的那样，偏差的符号取决于透镜光度函数αd的局部斜率，当αd< 1时，质量偏低，当αd> 1时，质量偏高。 虽然源的放大效应很少超过测量的GGL信号的1%，但未来弱透镜调查的统计能力保证了对这种效应的校正。
Magnification changes the observed local number density of galaxies on the sky. This biases the observed tangential shear profiles around galaxies: the so-called galaxy-galaxy lensing (GGL) signal. Inference of physical quantities, such as the mean mass profile of halos around galaxies, are correspondingly affected by magnification effects. We used simulated shear and galaxy data from the Millennium Simulation to quantify the effect on shear and mass estimates from the magnified lens and source number counts. The former is due to the large-scale matter distribution in the foreground of the lenses; the latter is caused by magnification of the source population by the matter associated with the lenses. The GGL signal is calculated from the simulations by an efficient fast Fourier transform, which can also be applied to real data. The numerical treatment is complemented by a leading-order analytical description of the magnification effects, which is shown to fit the numerical shear data well. We find the magnification effect is strongest for steep galaxy luminosity functions and high redshifts. For a KiDS+VIKING+GAMA-like survey with lens galaxies at redshiftzd= 0.36 and source galaxies in the last three redshift bins with a mean redshift of , the magnification correction changes the shear profile up to 2%, and the mass is biased by up to 8%. We further considered an even higher redshift fiducial lens sample atzd= 0.83, with a limited magnitude of 22 mag in ther-band and a source redshift ofzs= 0.99. Through this, we find that a magnification correction changes the shear profile up to 45% and that the mass is biased by up to 55%. As expected, the sign of the bias depends on the local slope of the lens luminosity functionαd, where the mass is biased low forαd< 1 and biased high forαd> 1. While the magnification effect of sources is rarely more than 1% of the measured GGL signal, the statistical power of future weak lensing surveys warrants correction for this effect.
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影响因子：
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