论文标题

VMC调查-XLVIII。经典的头孢虫揭示了LMC的3D几何形状

The VMC Survey -- XLVIII. Classical Cepheids unveil the 3D geometry of the LMC

论文作者

Ripepi, V., Chemin, L., Molinaro, R., Cioni, M. R. L., Bekki, K., Clementini, G., de Grijs, R., De Somma, G., Youssoufi, D. El, Girardi, L., Groenewegen, M. A. T., Ivanov, V., Marconi, M., McMillan, P. J., van Loon, J. Th.

论文摘要

我们采用了{\ it Vista近红外$ yjk_ \ mathrm {s} $调查麦芽岩系统}(vmc),分析$ y,\,j,j,j,j \,k_ \ mathrm {s} $ copheid sstars(dceps)的$ y mathrm {s}我们的样本由4408个对象组成,占OGLE \,IV和{\ IT GAIA} \,DR2 DCEPS的组合列表的97%。我们确定了各种时期luminitos($ pl $)和基本(F)和第一张开(1o)脉动器的时期$ pw $关系。我们首次在这些关系中发现了1o dceps $ p $ = 0.58 d。我们以$ \ sim $ 1 kpc的精度得出了LMC中DCEP的相对个性距离,计算了节点线的位置角度和星系的倾斜度:$θ$ = 145.6 $ \ pm $ 1.0°$ = 25.7 $ \ pm $ 0.4 $ $ 0.4°$ 0.4度。条形和光盘在不同的视角下看到。我们计算了脉动器的年龄,发现了持续$ \ sim $ 40 Myr的两个主要剧集,发生在93和159 Myr以前。 LMC可能是由于其过去与SMC的相互作用而导致的,其结构相当可观:将栏分为两个不同的部分,即东部和西部,彼此相互偏离超过1 kpc。螺旋臂显示了类似的行为。 LMC光盘显示为“爆发”且厚度,圆盘尺度高度为$ h \ sim 0.97 $ kpc。可以通过与银河系的强烈潮汐相互作用和/或现在被干扰的LMC卫星合并事件来解释此功能。

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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