Detection of Lyman-Break Galaxies (LBGs) at high-redshift can be affected by gravitational lensing induced by foreground deflectors not only in galaxy clusters, but also in blank fields. We quantify the impact of strong magnification in the samples of $B$, $V$, $i$, $z$ $\&$ $Y$ LBGs ($4\lesssim z \lesssim8$) observed in the XDF and GOODS/CANDELS fields, by investigating the proximity of dropouts to foreground objects. We find that $\sim6\%$ of bright LBGs ($m_{H_{160}}<26$) at $z\sim7$ have been strongly lensed ($μ>2$) by foreground objects. This fraction decreases from $\sim 3.5\%$ at $z\sim6$ to $\sim1.5\%$ at $z\sim4$. Since the observed fraction of strongly lensed galaxies is a function of the shape of the luminosity function (LF), it can be used to derive Schechter parameters, $α$ and $M_{\star}$, independently from galaxy number counts. Our magnification bias analysis yields Schechter-function parameters in close agreement with those determined from galaxy counts albeit with larger uncertainties. Extrapolation of our analysis to $z\gtrsim 8$ suggests that future surveys with JSWT, WFIRST and EUCLID should find excess LBGs at the bright-end, even if there is an intrinsic exponential cutoff of number counts. Finally, we highlight how the magnification bias measurement near the detection limit can be used as probe of the population of galaxies too faint to be detected. Preliminary results using this novel idea suggest that the magnification bias at $M_{UV}\sim -18$ is not as strong as expected if $α\lesssim -1.7$ extends well below the current detection limits in the XDF. At face value this implies a flattening of the LF at $M_{UV}\gtrsim-16.5$. However, selection effects and completeness estimates are difficult to quantify precisely. Thus, we do not rule out a steep LF extending to $M_{UV}\gtrsim -15$.
Measurement of Galaxy Clustering at z~7.2 and the Evolution of Galaxy Bias from 3.8<z<8 in the XDF, GOODS-S AND GOODS-N
在再电离（$z\gtrsim6$）期间用哈勃太空望远镜的宽视场相机3观察到的莱曼-布雷克星系（LBG）样本达到了足以表征其聚类特性的大小。使用哈勃极深场和坎德尔巡天的组合星表，包含z>6.5的$N=743$ LBG候选者，平均红移为$z=7.2$，我们在$\sim4σ$的角相关函数（ACF）中检测到清晰的聚类信号，对应于实空间相关长度$r_{0}=6.7^{+0.9}_{-1.0}h^{-1}$ cMpc。导出的星系偏差$b=8.6^{+0.9}_{-1.0}$是$z=7.2$的$M=10^{11.1^{+0.2}_{-0.3}}$ M $_{\odot}$的暗物质晕，并强调低于当前检测限（$M_{AB}\sim-17.7$）的星系预计在较低质量的晕（$M\sim10^{8}-10^{10.5}$ M $_{\odot}$）。我们计算ACF的LBG在$z\sim3.8-z\sim5.9$在相同的调查。从$z=3.8$（$b\sim3.0$）到$z=7.2$（$b\sim8.6$），发现了一个偏差增加的趋势，这与在$4<z<6$的类似质量的暗物质晕中托管的固定光度的星系大致一致，随后在$z\sim7$的晕质量略有上升（$\sim2σ$置信度）。在$z=7.2$样本（$M_{UV}=-19.4$）的中等光度下分离数据显示，与暗淡星系（$r_{0}=1.9^{+1.1}_{-1.0}h^…
Galaxy Stellar Mass Functions from z~10 to z~6 using the Deepest Spitzer/IRAC Data: No Significant Evolution in the Stellar-to-Halo Mass Ratio of Galaxies in the First Gyr of Cosmic Time
First Frontier Field Constraints on the Cosmic Star-Formation Rate Density at z~10 - The Impact of Lensing Shear on Completeness of High-Redshift Galaxy Samples
