用宇宙学模拟检验z~2质量星系团内禀星系大小和质量的恢复
Testing the Recovery of Intrinsic Galaxy Sizes and Masses of z~2 Massive Galaxies Using Cosmological Simulations
摘要：
精确测量星系的质量和大小是追踪星系随时间演化的关键。宇宙学放大模拟提供了一个理想的测试平台，用于评估从观测中恢复星系属性。在这里，我们利用星系与$M_*\sim10^{10}-10^{11.5}M_{\odot}$在z~1.7-2的MassiveFIRE宇宙学模拟套件，在现实环境中的反馈（FIRE）项目的一部分。使用模拟多波段图像，我们比较固有的星系质量和大小的观测估计。我们发现，观测准确地恢复恒星质量，轻微的平均低估~0.06德克斯和~0.15德克斯散射。当在所有视角上取平均值时，所述半光半径与固有半质量半径很好地一致，其中系统偏移为~0.1 dex（半光半径较大）并且散射为~0.2 dex。当使用颜色梯度来解释质量到光的变化时，恢复的半质量半径也超过固有的半质量半径约0.1 dex。然而，如果不适当地考虑，孔径效应可以使尺寸估计偏差约0.1 dex。恒星形成星系和静止星系的质量和大小偏移之间没有差异。视角的变化是造成恢复质量和尺寸散射的25%。因此，我们的研究结果表明，在质量大小关系的内在散射可能被高估了约25%。此外，方向驱动散射导致超大质量星系的数密度在$M_*\sim10^{11.5}M_{\odot}$被高估了约0.5 dex。
英文摘要：
Accurate measurements of galaxy masses and sizes are key to tracing galaxy evolution over time. Cosmological zoom-in simulations provide an ideal test bed for assessing the recovery of galaxy properties from observations. Here, we utilize galaxies with $M_*\sim10^{10}-10^{11.5}M_{\odot}$ at z~1.7-2 from the MassiveFIRE cosmological simulation suite, part of the Feedback in Realistic Environments (FIRE) project. Using mock multi-band images, we compare intrinsic galaxy masses and sizes to observational estimates. We find that observations accurately recover stellar masses, with a slight average underestimate of ~0.06 dex and a ~0.15 dex scatter. Recovered half-light radii agree well with intrinsic half-mass radii when averaged over all viewing angles, with a systematic offset of ~0.1 dex (with the half-light radii being larger) and a scatter of ~0.2 dex. When using color gradients to account for mass-to-light variations, recovered half-mass radii also exceed the intrinsic half-mass radii by ~0.1 dex. However, if not properly accounted for, aperture effects can bias size estimates by ~0.1 dex. No differences are found between the mass and size offsets for star-forming and quiescent galaxies. Variations in viewing angle are responsible for ~25% of the scatter in the recovered masses and sizes. Our results thus suggest that the intrinsic scatter in the mass-size relation may have previously been overestimated by ~25%. Moreover, orientation-driven scatter causes the number density of very massive galaxies to be overestimated by ~0.5 dex at $M_*\sim10^{11.5}M_{\odot}$.
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