论文标题
NGC1052-DF2和NGC1052-DF4中异常球状簇的复杂光度函数
A Complex Luminosity Function for the Anomalous Globular Clusters in NGC1052-DF2 and NGC1052-DF4
论文作者
论文摘要
NGC1052-DF2和NGC1052-DF4是超水型星系（UDGS），被发现具有极低的速度分散体，表明它们几乎没有或没有暗物质。这两个星系都有异常发光的球状簇（GC）系统，其GC光度函数（GCLF）的峰值比$ \ sim1.5 $ adududes的峰值高于$ m_v \ $ m_v \ $ -7.5 $。在这里，我们对两个星系的关节GCLF进行了分析，利用了新的HST光度法和凯克光谱法，以及最近改进的距离测量值。我们对DF2和DF4的联合GC样品应用均匀的光度法选择方法。新的分析表明，组合的GC光度函数的峰值保持在$ M_V \约-9 $ mag。此外，我们发现在$ M_V \ $ -7.5 $ mag的较小发光GC的亚群中，近乎全世界的GCLF峰位于其中。 $ -5 $至$ -8 $的GCS数量为$ 7.1 _ { - 4.34}^{+7.33} $在DF2中和$ 8.6 _ { - 4.83}^{+7.74} $在DF4中，与其他同一亮度相同的Galaxies中的预期。 DF2的$ -5 $ of $ -5 $ of $ -5 $ of $ -5 $至$ -11 $是$ 18.5 _ { - 4.42}^{+8.99} $，df2的$和$ 18.6 _ { - 4.92}^{+9.37} $的DF4，从df4的df4中计算出来，从df4的df4中计算出来。两个星系中更新的GC总数为$ 37^{+11.08} _ { - 6.54} $。在DF2或DF4中，GC的数量均不与光晕质量扩展，这表明$ N_ {GC} $不是直接通过Halos的合并来确定的。
NGC1052-DF2 and NGC1052-DF4 are ultra-diffuse galaxies (UDGs) that were found to have extremely low velocity dispersions, indicating that they have little or no dark matter. Both galaxies host anomalously luminous globular cluster (GC) systems, with a peak magnitude of their GC luminosity function (GCLF) that is $\sim1.5$ magnitudes brighter than the near-universal value of $M_V \approx -7.5$. Here we present an analysis of the joint GCLF of the two galaxies, making use of new HST photometry and Keck spectroscopy, and a recently improved distance measurement. We apply a homogeneous photometric selection method to the combined GC sample of DF2 and DF4. The new analysis shows that the peak of the combined GC luminosity function remains at $M_V \approx -9$ mag. In addition, we find a subpopulation of less luminous GCs at $M_V \approx -7.5$ mag, where the near-universal GCLF peak is located. The number of GCs in the magnitude range of $-5$ to $-8$ is $7.1_{-4.34}^{+7.33}$ in DF2 and $8.6_{-4.83}^{+7.74}$ in DF4, similar to that expected from other galaxies of the same luminosity. The total GC number between $M_V$ of $-5$ to $-11$ is $18.5_{-4.42}^{+8.99}$ for DF2 and $18.6_{-4.92}^{+9.37}$ for DF4, calculated from the background-subtracted GCLF. The updated total number of GCs in both galaxies is $37^{+11.08}_{-6.54}$. The number of GCs do not scale with the halo mass in either DF2 or DF4, suggesting that $N_{GC}$ is not directly determined by the merging of halos.
