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arXiv 1602.01840astro-ph.GA
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VIMOS超深巡天中含$2<z<4.5$的恒星形成星系的尺寸演化

Size evolution of star-forming galaxies with $2<z<4.5$ in the VIMOS Ultra-Deep Survey

B. Ribeiro, O. Le Fèvre, L. A. M. Tasca, B. C. Lemaux, P. Cassata, B. Garilli, D. Maccagni, G. Zamorani, E. Zucca, R. Amorín, S. Bardelli, A. Fontana, M. Giaval… 展开作者

B. Ribeiro, O. Le Fèvre, L. A. M. Tasca, B. C. Lemaux, P. Cassata, B. Garilli, D. Maccagni, G. Zamorani, E. Zucca, R. Amorín, S. Bardelli, A. Fontana, M. Giavalisco, N. P. Hathi, A. Koekemoer, J. Pforr, L. Tresse, J. Dunlop

备注：
22 pages, 20 figures (+3 in appendix), submitted to A&A
发表信息：
A&A 593, A22 (2016)
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摘要：

在VIMOS超深巡天（VUDS）中，我们测量了$\sim1200$星系样本的星系尺寸，这些星系具有确认的光谱红移$2 \leq z_{spec} \leq 4.5$，代表具有$i_\mathrm{AB} \leq 25$的恒星形成星系。我们首先推导出星系的大小应用经典的参数轮廓拟合方法，使用GALFIT。然后，我们测量的总像素面积超过一个给定的表面亮度阈值，克服了测量星系的大小与不规则形状的困难。然后，我们比较了获得的结果的等效圆半径包围100\%的测量星系光$r_T^{100}$与获得的有效半径$r_{e,\mathrm{circ}}$与GALFIT测量。我们发现，我们的非参数方法计算的星系的大小跨越一个大的范围内，但平均保持大致恒定的中值$r_T^{100}\sim2.2$ kpc的星系与$2<z<4.5$。这与$r_e$强烈的向下演化形成鲜明对比，随着红移的增加，$r_e$的大小下降到$z\sim4.5$的$<1$ kpc。我们分析了差异，发现复杂的，不对称的，多成分的星系的参数拟合严重低估了它们的大小。通过比较$r_T^{100}$和通过SED拟合得到的物理参数，我们发现在任何红移下最大的恒星形成星系平均来说质量更大，恒星形成更多。我们发现当我们向更高的红移移动时，星系呈现出更集中的光分布。我们将这些结果解释为几个可能不同的星系在早期组装阶段的演化路径的签名，包括多个明亮区域的主要和次要合并或恒星形成。（节略）

英文摘要：

We measure galaxy sizes on a sample of $\sim1200$ galaxies with confirmed spectroscopic redshifts $2 \leq z_{spec} \leq 4.5$ in the VIMOS Ultra Deep Survey (VUDS), representative of star-forming galaxies with $i_\mathrm{AB} \leq 25$. We first derive galaxy sizes applying a classical parametric profile fitting method using GALFIT. We then measure the total pixel area covered by a galaxy above a given surface brightness threshold, which overcomes the difficulty of measuring sizes of galaxies with irregular shapes. We then compare the results obtained for the equivalent circularized radius enclosing 100\% of the measured galaxy light $r_T^{100}$ to those obtained with the effective radius $r_{e,\mathrm{circ}}$ measured with GALFIT. We find that the sizes of galaxies computed with our non-parametric approach span a large range but remain roughly constant on average with a median value $r_T^{100}\sim2.2$ kpc for galaxies with $2<z<4.5$. This is in stark contrast with the strong downward evolution of $r_e$ with increasing redshift, down to sizes of $<1$ kpc at $z\sim4.5$. We analyze the difference and find that parametric fitting of complex, asymmetric, multi-component galaxies is severely underestimating their sizes. By comparing $r_T^{100}$ with physical parameters obtained through SED fitting we find that the star-forming galaxies that are the largest at any redshift are, on average, more massive and more star-forming. We discover that galaxies present more concentrated light profiles as we move towards higher redshifts. We interpret these results as the signature of several, possibly different, evolutionary paths of galaxies in their early stages of assembly, including major and minor merging or star-formation in multiple bright regions. (abridged)

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