VMC调查- XLVIII。经典造父变星揭开了LMC的3D几何结构
The VMC Survey -- XLVIII. Classical Cepheids unveil the 3D geometry of the LMC
摘要：
利用\it VISTA近红外$YJK_\mathrm{s}$麦哲伦星系巡天（VMC），分析了大麦哲伦星云（LMC）中造父$δ$星（DCEP）的$Y,\,J,\,K_\mathrm{s}$光变曲线。我们的样本由4408个天体组成，占OGLE、IV和{PDMATHAMM Gaia}、DR 2 DCEP合并列表的97%。我们确定了各种周期光度（$PL$）和周期Wesenchmann $PW$关系的基本（F）和第一泛音（1 O）的闪烁。我们首次发现，在$P$ =0.58 d时，10个DCEP的这些关系出现了断裂。我们导出了大麦哲伦星系中DCEP的相对距离，精度为$\sim$ 1 kpc，计算了节点线的位置角和星系倾角：$θ$ =145.6 $\pm$ 1.0 deg和$i$ =25.7 $\pm$ 0.4 deg。在不同的视角下可以看到杆和圆盘。我们计算了这些活动的年龄，发现DCEP形成的两个主要事件持续了$\sim$ 4000万年，分别发生在9300万年前和15900万年前。可能是由于它过去与SMC的相互作用，LMC显示出非平面分布，具有相当大的结构：酒吧分为两个不同的部分，东部和西部相互位移超过1千秒差距。旋臂也表现出类似的行为。大麦哲伦星云的星盘呈“喇叭状”且较厚，星盘刻度高度为$h\sim 0.97$千秒差距。这一特征可以通过与银河系和/或小麦哲伦云的强烈潮汐相互作用或过去与现在被破坏的LMC卫星的合并事件来解释。
英文摘要：
We employed the {\it VISTA near-infrared $YJK_\mathrm{s}$ survey of the Magellanic System} (VMC), to analyse the $Y,\,J,\,K_\mathrm{s}$ light curves of $δ$ Cepheid stars (DCEPs) in the Large Magellanic Cloud (LMC). Our sample consists of 4408 objects accounting for 97 per cent of the combined list of OGLE\,IV and {\it Gaia}\,DR2 DCEPs. We determined a variety of period-luminosity ($PL$) and period-Wesenheit $PW$ relationships for Fundamental (F) and First Overtone (1O) pulsators. We discovered for the first time a break in these relationships for 1O DCEPs at $P$=0.58 d. We derived relative individual distances for DCEPs in the LMC with a precision of $\sim$1 kpc, calculating the position angle of the line of nodes and inclination of the galaxy: $θ$=145.6$\pm$1.0 deg and $i$=25.7$\pm$0.4 deg. The bar and the disc are seen under different viewing angles. We calculated the ages of the pulsators, finding two main episodes of DCEP formation lasting $\sim$40 Myr which happened 93 and 159 Myr ago. Likely as a result of its past interactions with the SMC, the LMC shows a non-planar distribution, with considerable structuring: the bar is divided into two distinct portions, the eastern and the western displaced by more than 1 kpc from each other. Similar behaviour is shown by the spiral arms. The LMC disc appears "flared" and thick, with a disc scale height of $h\sim 0.97$ kpc. This feature can be explained by strong tidal interactions with the Milky Way and/or the Small Magellanic Cloud or past merging events with now disrupted LMC satellites.
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