Properties of Resolved Star Clusters in M51
Properties of Resolved Star Clusters in M51
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DOI：
10.1086/491786
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发表时间：
2005-10
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影响因子：
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通讯作者：
M. Lee;R. Chandar;B. Whitmore
中科院分区：
文献类型：
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作者：
M. Lee;R. Chandar;B. Whitmore
我们基于哈勃太空望远镜（HST） WFPC2的多滤光档案图像，对邻近的相互作用星系NGC 5194/5195 （M51）中的致密星团进行了研究。我们已经在两个星系系统的5个HST WFPC2场中检测到~ 400个孤立的、已分解的星团。由于我们要求仅根据它们的形态来检测星团，这导致选择相对孤立的物体，我们估计由于螺旋臂和恒星形成区域的极端拥挤，我们错过了大多数（4-6倍）小于10 Myr的星团。因此，我们将重点放在年龄超过10亿岁的群集人口上。探测到的星系团的年龄分布在100 - 500 Myr之间有一个宽峰，这与伴星NGC 5195通过NGC 5194盘的穿越时间在单次和多次穿越动力学模型中估计的一致。我们估计，在这个时间间隔内，从恒定的簇形成速率来看，峰值包含的簇比预期的多2.2-2.5倍。虽然在集群年龄分布中也有证据表明在100和500 Myr附近存在个别峰值（与多通道模型的预测一致），但这一结果需要验证。我们估计了样本簇的有效半径，并找到了约3-4个pc的中值。此外，我们发现在~ 4 σ水平上，聚类大小（增加）与聚类质量（最佳拟合斜率为0.14±0.03）相关，在3 σ水平上与聚类年龄（0.06±0.02）相关。最后，我们首次报道了在伴星NGC 5195（一个s0星系）中发现的暗淡的、扩展的星团。它们的颜色为红色[(V - I) >.0]，有效半径为bbb7pc，散布在NGC 5195的圆盘上。因此，我们的结果表明，NGC 5195是目前已知的第三个形成所谓暗淡模糊星团的棒状透镜星系。
We present a study of compact star clusters in the nearby pair of interacting galaxies NGC 5194/5195 (M51), based on multifilter Hubble Space Telescope (HST) WFPC2 archival images. We have detected ∼400 isolated, resolved clusters in five HST WFPC2 fields of the two-galaxy system. Due to our requirement that the clusters be detected based only on their morphology, which results in the selection of relatively isolated objects, we estimate that we are missing the majority (by a factor of 4–6) of clusters younger than ∼10 Myr due to the extreme crowding in the spiral arms and star-forming regions. Hence, we focus on the cluster population older than 10 Myr. An age distribution of the detected clusters shows a broad peak between 100 and 500 Myr, which is consistent with the crossing times of the companion galaxy NGC 5195 through the NGC 5194 disk estimated in both single- and multiple-passage dynamical models. We estimate that the peak contains ∼2.2–2.5 times more clusters than expected from a constant rate of cluster formation over this time interval. While there is also evidence for individual peaks near 100 and 500 Myr in the cluster age distribution (consistent with the predictions of multiple-passage models), this result requires verification. We estimate the effective radii of our sample clusters and find a median value of ∼3–4 pc. In addition, we see correlations of (increasing) cluster size with cluster mass (with a best-fit slope of 0.14 ± 0.03) at the ∼4 σ level, and with cluster age (0.06 ± 0.02) at the 3 σ level. Finally, we report for the first time the discovery of faint, extended star clusters in the companion, NGC 5195, an SB0 galaxy. These have red [(V - I) > 1.0] colors and effective radii >7 pc, and are scattered over the disk of NGC 5195. Our results therefore indicate that NGC 5195 is currently the third known barred lenticular galaxy to have formed so-called faint fuzzy star clusters.