We confirm the existence of a second Large Magellanic Cloud (LMC) star cluster, KMHK 1592, with an age that falls in the middle of the so-called LMC star cluster age gap, a long period of time (~ 4 - 11 Gyr) where no star cluster had been uncovered, except ESO121-SC03. The age (8.0+-0.5 Gyr) and the metallicity ([Fe/H]=-1.0+-0.2 dex) of KMHK1592 were derived from the fit of theoretical isochrones to the intrinsic star cluster colour-magnitude diagram sequences, which were unveiled using a robust star-by-star membership probability procedure. Because of the relative low brightness of the star cluster, deep GEMINI GMOS images were used. We discuss the pros and cons of three glimpsed scenarios that could explain the presence of both LMC age gap star clusters in the outskirts of the LMC, namely: in-situ star cluster formation, capture from the Small Magellanic Cloud, or accretion of a small dwarf galaxy.
The YMCA (Yes, Magellanic Clouds Again) and STEP ({The SMC in Time: Evolution of a Prototype interacting late-type dwarf galaxy) projects are deep g,i photometric surveys carried out with the VLT Survey Telescope (VST) and devoted to study the outskirts of the Magellanic System. A main goal of YMCA and STEP is to identify candidate stellar clusters and complete their census out to the outermost regions of the Magellanic Clouds. We adopted a specific over-density search technique coupled with a visual inspection of the color magnitude diagrams (CMDs) to select the best candidates and estimate t…
Revealing the Chemical Structure of the Magellanic Clouds with APOGEE. I. Calculating Individual Stellar Ages of RGB Stars in the Large Magellanic Cloud
Recently, a noticeable number of new star clusters was identified in the outskirts of the Large Magellanic Cloud (LMC) populating the so-called star cluster age gap, a space of time (~ 4-12 Gyr) where the only known star cluster is up-to-date ESO121-SC\,03. We used Survey of the Magellanic Stellar History (SMASH) DR2 data sets, as well as those employed to identify these star cluster candidates, to produce relatively deep color-magnitude diagrams (CMDs) of 17 out of 20 discovered age gap star clusters with the aim of investigating them in detail. Our analysis relies on a thorough CMD cleaning …
I revisited the age of the Small Magellanic Cloud cluster HW 42, whose previous estimates differ in more than 6 Gyr, thus challenging the most updated knowledge of the SMC star formation history. I performed an analysis of number stellar density profiles at different brightness levels; carried out a field star decontamination of the cluster color-magnitude diagram; and estimated the cluster fundamental parameters from the minimization of likelihood functions and their uncertainties from standard bootstrap methods. I conclude that HW 42 is a 6.2$^{\rm +1.6}_{\rm -1.3}$ Gyr old ([Fe/H] = -0.89$^…
The X-ray emission from a supernova remnant is a powerful diagnostic of the state of its shocked plasma. The temperature and the emission measure are related to the energy of the explosion, the age of the remnant, and the density of the surrounding medium. Here we present the results of a study of the remnant population of the Small Magellanic Cloud. Progress in X-ray observations of remnants has resulted in a sample of 20 remnants in the Small Magellanic Clound with measured temperatures and emission measures. We apply spherically symmetric supernova remnant evolution models to this set of re…
The outer northeastern region of the Small Magellanic Cloud (SMC) is populated by a shell-like overdensity whose nature was recently investigated. We analyzed twenty catalogued star clusters projected onto it from Survey of the MAgellanic Stellar History data sets. After carrying out a cleaning of field stars in the star cluster colour-magnitude diagrams (CMDs), and deriving their astrophysical properties from the comparison between the observed and synthetic CMDs, we found that four objects are not genuine star clusters, while the remaining ones are young star clusters (11, age $\sim$ 30-200 …
We study 147 star clusters in the Large Magellanic Cloud (LMC) in order to determine their mean metallicities and ages, as well as the mean metallicities of 80 surrounding fields. We construct an age-metallicity relation (AMR) for the clusters in the LMC. For this purpose, we used Strömgren photometry obtained with the SOI camera on the 4.1 m SOAR telescope. We found the mean metallicity and age for 110 star clusters. For the remaining 37, we provide an age estimation only. To the best of our knowledge, for 29 clusters from our sample, we provide both the metallicity and age for the first time…
We present a three-dimensional structure of the Magellanic System using over 9 000 Classical Cepheids and almost 23 000 RR Lyrae stars from the OGLE Collection of Variable Stars. Given the vast coverage of the OGLE-IV data and very high completeness of the sample, we were able to study the Magellanic System in great details. We very carefully studied the distribution of both types of pulsators in the Magellanic Bridge area. We show that there is no evident physical connection between the Clouds in RR Lyrae stars distribution. We only see the two extended structures overlapping. There are few c…
New star cluster candidates projected toward the Large and Small Magellanic Clouds (L/SMC) have been recently discovered from relatively deep imaging surveys. We here conduct a sound analysis of 24 star cluster candidates located in the outer regions of the L/SMC using PSF photometry produced by the Survey of the Magellanic Stellar History. With only one exception, the studied objects resulted to be genuine stellar aggregates. We conclude on their physical reality once their observed color-magnitude diagrams (CMDs) were statistically decontaminated by the presence of field stars, and the resul…
Hubble Space Telescope proper motions of Large Magellanic Cloud star clusters -- II. Kinematic structure of young and intermediate-age clusters
Leibniz-Institut für Astrophysik Potsdam（波茨坦阿佩尔天体物理研究所）；INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（博洛尼亚天文物理学与空间科学国家研究院）；Donostia International Physics Center (DIPC)（圣塞巴斯蒂安国际物理中心）；IKERBASQUE, Basque Foundation for Science（伊克尔巴斯基克科学基金会）；Space Telescope Science Institute（太空望远镜科学研究所）；atlanTTic, Universidade de Vigo, Escola de Enxeñaría de Telecomunicación（维戈大学电信工程学院阿特兰提克）；Universidad de La Laguna（拉帕鲁纳大学）；INAF – Osservatorio Astronomico d’ Abruzzo（阿布鲁佐天文台国家研究院）；INFN – Sezione di Pisa, Universitá di Pisa（比萨大学意大利国家核物理研究所比萨分部）；Department of Physics, University of Surrey（萨里大学物理系）；INAF - Osservatorio Astronomico di Padova（帕多瓦天文台国家研究院）
We derive the spatially-resolved star formation history (SFH) for a $96$ deg$^2$ area across the main body of the Large Magellanic Cloud (LMC), using the near-infrared photometry from the VISTA survey of the Magellanic Clouds (VMC). The data and analyses are characterised by a great degree of homogeneity and a low sensitivity to the interstellar extinction. 756 subregions of size $0.125$ deg$^2$ -- corresponding to projected sizes of about $296\times322\,\mathrm{pc}^{2}$ in the LMC -- are analysed. The resulting SFH maps, with typical resolution of $0.2$--$0.3$ dex in logarithm of age, reveal …
The apparent Large Magellanic Cloud star cluster age gap
Goethe-Universität Frankfurt（法兰克福歌德大学）；Instituto Interdisciplinario de Ciencias Básicas (ICB), CONICET-UNCuyo（基础科学跨研究所（ICB），CONICET-门多萨国立大学）；Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)（国家科学研究委员会）
Intermediate-age star clusters in the Magellanic Clouds harbour signatures of the multiple stellar populations long thought to be restricted to old globular clusters. We compare synthetic horizontal branch models with Hubble Space Telescope photometry of clusters in the Magellanic Clouds, with age between ~2 and ~10 Gyr, namely NGC 121, Lindsay 1, NGC 339, NGC 416, Lindsay 38, Lindsay 113, Hodge 6 and NGC 1978. We find a clear signature of initial helium abundance spreads (delta(Y)) in four out of these eight clusters (NGC 121, Lindsay 1, NGC 339, NGC 416) and we quantify the value of delta(Y)…
Recent observations have found that the age distribution of star clusters (SCs) in the Small Magellanic Cloud (SMC) shows a sharp peak around 2 Gyr ago. However, it is theoretically unclear what physical processes are responsible for such sudden formation of SCs in the SMC. Here we investigate whether massive SCs with initial masses more than $10^5$ $\text{M}_\odot$ can be formed during tidal interaction of the SMC with the Large Magellanic Cloud (LMC) about 2 Gyr ago, based on our new simulations, which include molecular hydrogen formation on dust grains and SC formation within giant molecula…
The Magellanic Clouds are nearby dwarf irregular galaxies whose morphologies show different properties when traced by different stellar populations, making them an important laboratory for studying galaxy morphologies. We study the morphology of the Magellanic Clouds using data from the VISTA survey of the Magellanic Clouds system (VMC). We used about $10$ and $2.5$ million sources across an area of $\sim105$ deg$^2$ and $\sim42$ deg$^2$ towards the Large and Small Magellanic Cloud (LMC and SMC), respectively. We estimated median ages of stellar populations occupying different regions of the n…
The Minimum Mass of Rotating Main Sequence Stars and its Impact on the Nature of Extended Main Sequence Turnoffs in Intermediate-Age Star Clusters in the Magellanic Clouds
扩展主序星关闭（eMSTO）是麦哲伦星云中年轻和中等年龄星团色星等图（CMD）的一个共同特征。eMSTO的性质仍有争议。最受欢迎的场景是扩展的恒星形成和恒星旋转速率的范围。本文研究了大麦云星云（LMC）中年轻星团主序（MS）中扭结特征的含义。在对7亿年前的星系团NGC 1831进行的新的\emph{Hubble Space Telescope}观测中，这种扭折非常清楚地显示出来，并且位于CMD中多个或宽的MS合并成一个MS的区域之下，这些MS已知出现在年轻的星系团中，并且被认为是由于旋转速率的变化，扭折发生在初始恒星质量为$1.45 \pm 0.02\;M_{\odot}$的时候;我们认为，它代表了一个质量下限，低于这个下限，在这些星团的金属丰度下，自转对恒星能量输出的影响可以忽略不计。评估的位置，这样的初始质量的恒星在CMD的大规模LMC星团的年龄为$\sim\,$ 1.7 Gyr的功能广泛的eMSTO，我们发现，这样的恒星位于一个区域的eMSTO已经显着宽比MS下面it. This强烈建议恒星旋转\emph{cannot}充分解释了广泛的eMSTO在大规模的中期年龄集群的麦哲伦云。恒星年龄的分布似乎仍然需要解释eMSTO现象。
