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arXiv 1801.02776astro-ph.GA
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基于稳健互相关的半导体激光束团尺寸测量

Robust Cross-correlation-based Measurement of Clump Sizes in Galaxies

Kamran Ali, Danail Obreschkow, David B. Fisher, Karl Glazebrook, Ivana Damjanov, Roberto G. Abraham, Robert Bassett

摘要:

恒星形成于分子复合体中,在红移为$z\approx1$ $-$ $3$时,在附近星系中可以看到巨大的云($\sim 10^{5-6} \mathrm{M}_\odot$),在星系中可以看到巨大的团块($\sim 10^{8-9}\mathrm{M}_\odot$)。这些复合物的起源和演化的理论推断往往需要强大的测量其特征尺寸,这是很难在有限的分辨率测量,往往不明确,由于重叠和准分形子结构。我们表明,在恒星形成图中看到的团块的最大和亮度加权大小(例如,H $α$)可以用两点关联函数(2 PCF)进行统计恢复。在解析地阐明高斯团簇与2 PCF之间的联系之后,我们设计了一种具有真实准分形子结构的高斯团簇直径测量方法。用不同空间分辨率的星团盘星系的模拟图像和高斯白噪声扰动对该方法进行了测试。我们发现,2 PCF可以恢复输入的团块规模在$\sim20\%$精度,只要这个规模是大于空间分辨率。我们应用这种方法的本地螺旋星系NGC 5194,以及三个cluerous湍流星系的DYNAMO-HST样本。在这两种情况下,我们的统计H $α$ -丛大小测量与以前的测量和估计的牛仔裤长度一致。然而,新的测量方法在拟合单个块时不受主观选择的影响。

英文摘要:

Stars form in molecular complexes that are visible as giant clouds ($\sim 10^{5-6} \mathrm{M}_\odot$) in nearby galaxies and as giant clumps ($\sim 10^{8-9}\mathrm{M}_\odot$) in galaxies at redshifts $z\approx1$$-$$3$. Theoretical inferences on the origin and evolution of these complexes often require robust measurements of their characteristic size, which is hard to measure at limited resolution and often ill-defined due to overlap and quasi-fractal substructure. We show that maximum and luminosity-weighted sizes of clumps seen in star formation maps (e.g.\ H$α$) can be recovered statistically using the two-point correlation function (2PCF), if an approximate stellar surface density map is taken as the normalizing random field. After clarifying the link between Gaussian clumps and the 2PCF analytically, we design a method for measuring the diameters of Gaussian clumps with realistic quasi-fractal substructure. This method is tested using mock images of clumpy disk galaxies at different spatial resolutions and perturbed by Gaussian white noise. We find that the 2PCF can recover the input clump scale at $\sim20\%$ accuracy, as long as this scale is larger than the spatial resolution. We apply this method to the local spiral galaxy NGC 5194, as well as to three clumpy turbulent galaxies from the DYNAMO-HST sample. In both cases, our statistical H$α$-clump size measurements agree with previous measurements and with the estimated Jeans lengths. However, the new measurements are free from subjective choices when fitting individual clumps.

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