THE STRUCTURE OF NUCLEAR STAR CLUSTERS IN NEARBY LATE-TYPE SPIRAL GALAXIES FROM HUBBLE SPACE TELESCOPE WIDE FIELD CAMERA 3 IMAGING
THE STRUCTURE OF NUCLEAR STAR CLUSTERS IN NEARBY LATE-TYPE SPIRAL GALAXIES FROM HUBBLE SPACE TELESCOPE WIDE FIELD CAMERA 3 IMAGING
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DOI：
10.1088/0004-6256/149/5/170
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发表时间：
2015-01
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影响因子：
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通讯作者：
Daniel J. Carson;A. Barth;A. Seth;M. D. Brok;M. Cappellari;J. Greene;L. Ho;Nadine Neumayer University of Californi
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作者：
Daniel J. Carson;A. Barth;A. Seth;M. D. Brok;M. Cappellari;J. Greene;L. Ho;Nadine Neumayer University of Californi
我们获得了哈勃空间望远镜/宽视场相机3成像的样本的10个最近的和最明亮的核集群（NC）居住在晚型螺旋星系，在7个波段，跨越近紫外线到近红外。集群的结构特性进行了测量，通过拟合二维表面亮度轮廓的图像使用GALFIT。星系团具有广泛的结构特性，F814 W的绝对星等介于−11.2至−15.1等，有效半径介于1.4至8.3秒差距。对于我们样本中的10个星团中的6个，我们发现有效半径随波长变化，表明径向变化的恒星种群。在其中四个天体中，有效半径随波长增加而增加，表明存在着比星团中大部分恒星更集中的年轻人口。然而，我们发现，在我们的样本中的两个对象，这可能表明扩展，环核星星形成的有效半径与波长的一般减少。我们还发现了一个总的趋势，增加圆度的集群在较长的波长，以及之间的相关性的轴比的NC和他们的宿主星系。这些观测结果表明，蓝盘与主星系平面对齐是晚型星系中NC的一个共同特征，但在接近正面的星系中很难检测到。在近紫外到近红外的色-色图中，大多数星系团远离单爆发演化轨道，显示出多年龄种群的证据。大多数集群的综合颜色与老年人口（>1 Gyr）和年轻人口（1亿至3亿）的混合一致。我们的数据的宽波长覆盖范围提供了一个敏感的人口与年龄的混合，这将是不可能实现的光学波段成像只。在这项工作中提出的表面亮度配置文件将用于未来的恒星种群建模和动力学研究的集群。
We obtained Hubble Space Telescope/Wide Field Camera 3 imaging of a sample of ten of the nearest and brightest nuclear clusters (NCs) residing in late-type spiral galaxies, in seven bands that span the near-UV to the near-IR. Structural properties of the clusters were measured by fitting two-dimensional surface brightness profiles to the images using GALFIT. The clusters exhibit a wide range of structural properties, with F814W absolute magnitudes that range from −11.2 to −15.1 mag and F814W effective radii that range from 1.4 to 8.3 pc. For 6 of the 10 clusters in our sample, we find changes in the effective radius with wavelength, suggesting radially varying stellar populations. In four of the objects, the effective radius increases with wavelength, indicating the presence of a younger population that is more concentrated than the bulk of the stars in the cluster. However, we find a general decrease in effective radius with wavelength in two of the objects in our sample, which may indicate extended, circumnuclear star formation. We also find a general trend of increasing roundness of the clusters at longer wavelengths, as well as a correlation between the axis ratios of the NCs and their host galaxies. These observations indicate that blue disks aligned with the host galaxy plane are a common feature of NCs in late-type galaxies, but are difficult to detect in galaxies that are close to face-on. In color–color diagrams spanning the near-UV through the near-IR, most of the clusters lie far from single-burst evolutionary tracks, showing evidence for multi-age populations. Most of the clusters have integrated colors consistent with a mix of an old population (>1 Gyr) and a young population (∼100–300 Myr). The wide wavelength coverage of our data provides a sensitivity to populations with a mix of ages that would not be possible to achieve with imaging in optical bands only. The surface brightness profiles presented in this work will be used for future stellar population modeling and dynamical studies of the clusters.