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arXiv 2011.04656astro-ph.GA
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从星系内部恒星质量分布看$z=2$以来的星系大小

Galaxy Sizes Since $z=2$ from the Perspective of Stellar Mass Distribution within Galaxies

Moein Mosleh, Shiva Hosseinnejad, S. Zahra Hosseini-ShahiSavandi, Sandro Tacchella

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32 pages, 15 figures and 3 appendices. Accepted for publication in ApJ
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摘要：

恒星质量如何在星系内聚集仍然是一个悬而未决的问题。我们目前的测量恒星质量分布的kpc尺度上的恒星质量高于$\sim5500$星系。我们创建恒星质量图从哈勃空间望远镜的观测通过逐像素的SED拟合方法。这些图用于从最佳拟合的Sérsic模型中推导出包含恒星总质量的$20\%$、$50\%$和$80\%$（$r_{20}$、$r_{50}$和$r_{80}$）的半径。结构参数测量的可靠性和局限性进行了广泛的检查使用大样本（$\sim3000$）的模拟星系。研究了恒星形成星系和静止星系的$r_{20}$、$r_{50}$和$r_{80}$的大小质量关系和红移演化。在固定的质量下，恒星形成星系的$r_{20}$、$r_{50}$和$r_{80}$的大小没有明显的变化，这表明它们是自相似的增长。只有在$\log(M_{\ast}/M_{\odot})\simeq10.5$的主恒星质量以上，$r_{80}$才演化为$r_{80}\propto(1+z)^{-0.85\pm0.20}$，这表明质量在这些系统的外围积累（由内向外生长）。对于大质量恒星形成星系，Sérsic值也会在宇宙时间后期增加。大质量静止星系在所有半径上都表现出更强的尺寸演化，特别是$r_{20}$尺寸。对于这些大质量星系，Sérsic值至少从$z\sim1.3$开始几乎保持不变，表明强烈的尺寸演化与这些星系外部的变化有关。我们公开了所有的结构参数。

英文摘要：

How stellar mass assembles within galaxies is still an open question. We present measurements of the stellar mass distribution on kpc-scale for $\sim5500$ galaxies with stellar masses above $\log(M_{\ast}/M_{\odot})\geqslant9.8$ up to the redshift $2.0$. We create stellar mass maps from Hubble Space Telescope observations by means of the pixel-by-pixel SED fitting method. These maps are used to derive radii encompassing $20\%$, $50\%$, and $80\%$ ($r_{20}$, $r_{50}$ and $r_{80}$) of the total stellar mass from the best-fit Sérsic models. The reliability and limitations of the structural parameter measurements are checked extensively using a large sample ($\sim3000$) of simulated galaxies. The size-mass relations and redshift evolution of $r_{20}$, $r_{50}$ and $r_{80}$ are explored for star-forming and quiescent galaxies. At fixed mass, the star-forming galaxies do not show significant changes in their $r_{20}$, $r_{50}$ and $r_{80}$ sizes, indicating self-similar growth. Only above the pivot stellar mass of $\log(M_{\ast}/M_{\odot})\simeq10.5$, $r_{80}$ evolves as $r_{80}\propto(1+z)^{-0.85\pm0.20}$, indicating that mass builds up in the outskirts of these systems (inside-out growth). The Sérsic values also increase for the massive star-forming galaxies towards late cosmic time. Massive quiescent galaxies show stronger size evolution at all radii, in particular the $r_{20}$ sizes. For these massive galaxies, Sérsic values remain almost constant since at least $z\sim1.3$, indicating that the strong size evolution is related to the changes in the outer parts of these galaxies. We make all the structural parameters publicly available.

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