Discovery of an Ultra-faint Stellar System near the Magellanic Clouds with the DECam Local Volume Exploration Survey
Discovery of an Ultra-faint Stellar System near the Magellanic Clouds with the DECam Local Volume Exploration Survey
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DOI：
10.3847/1538-4357/abe1af
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发表时间：
2020-09
期刊：
影响因子：
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通讯作者：
W. Cerny;A. Pace;A. Drlica-Wagner;P. Ferguson;S. Mau;M. Adamów;J. Carlin;Y. Choi;D. Erkal-D
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作者：
W. Cerny;A. Pace;A. Drlica-Wagner;P. Ferguson;S. Mau;M. Adamów;J. Carlin;Y. Choi;D. Erkal-D
我们报告了在DECam局部体积探测巡天中发现的麦哲伦云附近的一个新的超暗恒星系统。这个新的系统，DELVE J0155−6815（DELVE 2），位于日心距离D = 71 ± 4 kpc，这使它与小麦哲伦云中心和大麦哲伦云中心的三维物理距离为12 ± 3 kpc。DELVE 2被认为是一颗老恒星（τ > 13.3 Gyr）和贫金属恒星（dex）的高密度恒星，投影半光半径为，绝对星等为。DELVE 2的大小和光度与最近发现的超暗球状星团和最小的超暗矮星系的数量一致。然而，它的光度年龄和金属丰度将使它成为麦哲伦星系中最古老和最贫金属的球状星团之一。在没有光谱测量系统的金属丰度分散和内部运动学的情况下，我们无法在这个时候最终对这个系统进行分类。DELVE 2在盖亚DR2中被探测到，有清晰的自行信号，在系统质心附近有多颗蓝色水平分支恒星，自行与系统平均值一致。我们测得系统的自行为= mas yr−1。我们比较了DELVE 2的空间位置和自行与模拟的吸积卫星人口的LMC，发现它是非常有可能与LMC。
We report the discovery of a new ultra-faint stellar system found near the Magellanic Clouds in the DECam Local Volume Exploration Survey. This new system, DELVE J0155−6815 (DELVE 2), is located at a heliocentric distance of D ⊙ = 71 ± 4 kpc, which places it at a 3D physical separation of 12 ± 3 kpc from the center of the Small Magellanic Cloud and from the center of the Large Magellanic Cloud (LMC). DELVE 2 is identified as a resolved overdensity of old (τ > 13.3 Gyr) and metal-poor ( dex) stars with a projected half-light radius of and an absolute magnitude of . The size and luminosity of DELVE 2 are consistent with both the population of recently discovered ultra-faint globular clusters and the smallest ultra-faint dwarf galaxies. However, its photometrically derived age and metallicity would place it among the oldest and most metal-poor globular clusters in the Magellanic system. In the absence of spectroscopic measurements of the system’s metallicity dispersion and internal kinematics, we are unable to conclusively classify this system at this time. DELVE 2 is detected in Gaia DR2 with a clear proper-motion signal, with multiple blue horizontal-branch stars near the centroid of the system with proper motions consistent with the systemic mean. We measure the system proper motion to be = mas yr−1. We compare the spatial position and proper motion of DELVE 2 with simulations of the accreted satellite population of the LMC and find that it is very likely to be associated with the LMC.