We present 52-93 micron spectra, obtained with the Spitzer Space Telescope, of luminous compact far-IR sources in the SMC. These comprise 9 Young Stellar Objects (YSOs), the compact HII region N81 and a similar object within N84, and two red supergiants (RSGs). The spectra of the sources in N81 (of which we also show the ISO-LWS spectrum between 50-170 micron) and N84 both display strong [OI] 63-micron and [OIII] 88-micron fine-structure line emission. We attribute these lines to strong shocks and photo-ionized gas, respectively, in a ``champagne flow'' scenario. The nitrogen content of these two HII regions is very low, definitely N/O<0.04 but possibly as low as N/O<0.01. Overall, the oxygen lines and dust continuum are weaker in star-forming objects in the SMC than in the LMC. We attribute this to the lower metallicity of the SMC compared to that of the LMC. Whilst the dust mass differs in proportion to metallicity, the oxygen mass differs less; both observations can be reconciled with higher densities inside star-forming cloud cores in the SMC than in the LMC. The dust in the YSOs in the SMC is warmer (37-51 K) than in comparable objects in the LMC (32-44 K). We attribute this to the reduced shielding and reduced cooling at the low metallicity of the SMC. On the other hand, the efficiency of the photo-electric effect to heat the gas is found to be indistinguishable to that measured in the same manner in the LMC, 0.1-0.3%. This may result from higher cloud-core densities, or smaller grains, in the SMC. The dust associated with the two RSGs in our SMC sample is cool, and we argue that it is swept-up interstellar dust, or formed (or grew) within the bow-shock, rather than dust produced in these metal-poor RSGs themselves. Strong emission from crystalline water ice is detected in at least one YSO. (abridged)
With the entire Small Magellanic Cloud (SMC) mapped by the Spitzer Space Telescope and Herschel Space Observatory, we were able to search 8-250 micron images in order to identify infrared (IR) emission associated with SMC supernova remnants (SNRs). A valid detection had to correspond with known X-ray, Halpha and radio emission from the SNRs. From the 24 known SNRs, we made 5 positive detections with another 5 possible detections. Two detections are associated with pulsars or pulsar wind nebula, and another three detections are part of the extended nebulous emission from the SNRs. We modelled d…
Spitzer Characterization of Dust in the Ionized Medium of the Large Magellanic Cloud
迄今为止，对与电离气体有关的尘埃发射的系统研究仅在我们的银河系中进行，并且波长大于60 μm。新获得的斯皮策数据现在提供了在大麦云（LMC）中进行类似分析的机会。通过Spitzer SAGE（Surveying the Agents of a Galaxy's Evolution）数据与ATCA/Parkes HI 21-cm数据、NANTEN 12 CO（J=1-0）数据、SHASSA Hα和Parkes 6-cm数据的互相关，我们研究了与气体的不同相态（原子、分子和电离态）有关的尘埃的物理性质。特别是，我们研究了尘埃的存在和性质从3.6到160 μm和各种制度的电离气体，跨越发射措施（EM）从\sim 1 pc cm-6（扩散组件）到\sim 10^3 pc cm-6（HII区域）。使用尘埃排放模型，并测试我们的结果与几个辐射场光谱，我们表明，在电离气体中的尘埃是温暖的尘埃比与其他阶段（原子和分子）。我们还发现，减少多环芳烃（PAH）相对于大颗粒（BG）的相对丰度，以及增加的近红外（NIR）连续。这三个结果（例如，温暖的温度，减少PAH丰度和增加的近红外光谱连续）被发现一致的电离气体的所有制度。相反，分子相似乎为多环芳烃的生存提供了有利条件。此外，非常小的颗粒（VSG）的相对丰度往往增加电离阶段，特别是在明亮的HII区域。最后但并非最不重要的是，我们的分析表明，与电离气体相关的…
We present the mid-infrared (mid-IR) period$-$luminosity relations (PLRs) using over 1000 Mira variables in the Large Magellanic Cloud (LMC), for the four Wide-Field Infrared Survey Explorer (WISE) and the four Spitzer bands. These PLRs cover a mid-IR wavelength range from $3.4$ $μ$m to $22$ $μ$m and are presented separately for the oxygen-rich (O-rich) and carbon-rich (C-rich) Miras. These relations can be used to measure distances to individual O-rich and/or C-rich Mira stars with the accuracy of $5\%$ and $12\%$, respectively. They are the most accurate Mira PLRs in the mid-IR to date.
Modeling dust emission in the Magellanic Clouds with Spitzer and Herschel
尘埃模型对于推断星系研究的尘埃性质和预算至关重要。然而，尘埃颗粒模型之间存在系统差异，导致星系推断的尘埃性质存在相应的系统差异。量化这些系统需要一致的拟合分析。我们比较了输出的尘埃参数，并评估了两种尘埃颗粒模型Compiegne et al（2011）和THEMIS（Jones et al 2013，Kohler et al 2015）之间的差异。在这项研究中，我们使用一个单一的拟合方法应用于所有的模型，以提取一个连贯的和独特的统计分析。我们适合的模型，看到斯皮策和赫歇尔在小和大麦云云（SMC和LMC）的尘埃排放。这些观测涵盖了从几微米到亚毫米范围的红外（IR）光谱。对于每个拟合的像素，我们基于Gordon et al（2014）中描述的方法计算完整的n-D似然。自由参数是环境参数（$U$，星际辐射场强; $α_\mathrm{ISRF}$，多铀环境的幂律系数; $Ω^*$，星光强度）和模型固有参数（$Y_\mathrm{i}$：颗粒物质$i$的丰度; $α_\mathrm{sCM20}$，小碳颗粒尺寸分布的系数）。5组不同参数的分数残差表明，拟合THEMIS比Compiegne模型更准确地再现了观测结果。然而，独立的尘埃物种的变化表现出很强的模型依赖性。我们发现，硅酸盐的丰度只能被限制在一个上限，硅酸盐/碳的比例与我们银河系中看到的不同。在LMC中，我们拟合的结果是尘埃质量略低于…
Variable stars have been used for over one hundred years as probes for determining astronomical distances; these distances can be used to map the three-dimensional (3D) structure of nearby galaxies. Exploiting the effect that moving to the mid-infrared has on Cepheid magnitudes and light curves, we can now map our nearest galaxies in 3D at fidelities never before achievable. Combining data from the OGLE-IV catalogue with mid-infrared photometry from the Spitzer Space Telescope, around 5000 fundamental mode Cepheids are being used to trace the 3D structure of the Magellanic Clouds. An automated…
We investigate infrared properties of asymptotic giant branch (AGB) stars in our Galaxy and the Magellanic Clouds using various infrared observational data and theoretical models. We use catalogs for the sample of 4996 AGB stars in our Galaxy and about 39,000 AGB stars in the Magellanic Clouds from the available literature. For each object in the sample, we cross-identify the 2MASS, WISE, and Spitzer counterparts. To compare the physical properties of O-rich and C-rich AGB stars in our Galaxy and the Magellanic Clouds, we present IR two color diagrams (2CDs) using various photometric data. We …
Mid-infrared JWST spectra of carbon stars in the Large Magellanic Cloud
Space Telescope Science Institute（太空望远镜科学研究所）；University of North Carolina, Chapel Hill（北卡罗来纳大学教堂山分校）；Uppsala University（乌普萨拉大学）；University of Vienna（维也纳大学）；Boston College（波士顿学院）；The University of Western Ontario（韦仕敦大学）；Chalmers University of Technology（查尔姆斯理工大学）；Université Côte d’Azur（蔚蓝海岸大学）
The nearby Magellanic Clouds system covers more than 200 square degrees on the sky. Much of it has been mapped across the electromagnetic spectrum at high angular resolution and sensitivity X-ray (XMM-Newton), UV (UVIT), optical (SMASH), IR (VISTA, WISE, Spitzer, Herschel), radio (ATCA, ASKAP, MeerKAT). This provides us with an excellent dataset to explore the galaxy populations behind the stellar-rich Magellanic Clouds. We seek to identify and characterise AGN via machine learning algorithms on this exquisite data set. Our project focuses not on establishing sequences and distributions of com…
The survey for DUST In Nearby Galaxies with Spitzer (DUSTiNGS) has identified hundreds of candidate dust-producing Asymptotic Giant Branch (AGB) stars in several nearby metal-poor galaxies. We have obtained multi-epoch follow-up observations for these candidates with the Spitzer Space Telescope and measured their infrared (IR) lightcurves. This has allowed us to confirm their AGB nature and investigate pulsation behavior at very low metallicity. We have obtained high-confidence pulsation periods for 88 sources in seven galaxies. We have confirmed DUSTiNGS variable star candidates with a 20% su…
Studies of young stellar objects (YSOs) in the Galaxy have found that a significant fraction exhibit photometric variability. However, no systematic investigation has been conducted on the variability of extragalactic YSOs. Here we present the first variability study of massive YSOs in a $\sim 1.5\,\mathrm{deg^2}$ region of the Large Magellanic Cloud (LMC). The aim is to investigate whether the different environmental conditions in the metal-poor LMC ($\sim$ 0.4-0.5 Z_sun) have an impact on the variability characteristics. Multi-epoch near-infrared (NIR) photometry was obtained from the VISTA …
Surveys of Wolf-Rayet (WR) stars in the Large Magellanic Cloud (LMC) have yielded a fairly complete catalog of 154 known stars. We have conducted a comprehensive, multiwavelength study of the interstellar/circumstellar environments of WR stars, using the Magellanic Cloud Emission Line Survey (MCELS) images in the H$α$, [O III], and [S II] lines; Spitzer Space Telescope 8 and 24 $μ$m images; Blanco 4m Telescope H$α$ CCD images; and Australian Telescope Compact Array (ATCA) + Parkes Telescope H I data cube of the LMC. We have also examined whether the WR stars are in OB associations, classified …
The Cepheid Leavitt Law (LL), also known as the Period-Luminosity relation, is a crucial tool for assembling the cosmic distance ladder. By combining data from the OGLE-IV catalogue with mid-infrared photometry from the Spitzer Space Telescope, we have determined the $3.6$ $μ$m and $4.5$ $μ$m LLs for the Magellanic Clouds using around 5000 fundamental-mode Classical Cepheids. Mean magnitudes were determined using a Monte Carlo Markov Chain (MCMC) template fitting procedure, with template light curves constructed from a subsample of these Cepheids with fully-phased, well-sampled light curves. T…
As nearby neighbors to the Milky Way, the Large and Small Magellanic Clouds (LMC and SMC) provide a unique opportunity to study star formation in the context of their galactic ecosystems. Thousands of young stellar objects (YSOs) have been characterized with large-scale Spitzer and Herschel surveys. In this paper, we present new near-IR spectroscopy of five high-mass YSOs in the LMC and one in the SMC. We detect multiple hydrogen recombination lines, as well as He I 2.058 $μ$m, H$_2$, [Fe II], and [S III] in these highly excited sources. We estimate the internal extinction of each source and f…
A wide-field, multi-line survey of CO in the Magellanic Clouds at parsec-scale resolution: characterising the molecular gas content with a 50-m single-dish submillimeter telescope
ICE-CSIC/ICREA/IEEC（西班牙高等科学研究理事会/加泰罗尼亚高级研究院/加泰罗尼亚天体物理研究所）；MPIfR（马克斯·普朗克射电天文研究所）；Observatoire astronomique de Strasbourg（斯特拉斯堡天文台）；CEA/Saclay（法国原子能委员会萨克雷中心）；United Arab Emirates University（阿联酋大学）；U. Chile（智利大学）；Kagawa University（香川大学）
We present a catalog of star clusters, associations and related extended objects in the Small Magellanic Cloud and the Magellanic Bridge with 2741 entries, a factor 2 more than a previous version from a decade ago. Literature data till December 2018 are included. The identification of star clusters was carried out with digital atlases in various bands currently available in DSS and MAMA imaging surveys. In particular, we cross-identified recent cluster samples from the VMC, OGLE-IV and SMASH surveys, confirming new clusters and pointing out equivalencies. A major contribution of the present ca…
We present maps of the dust properties in the Small and Large Magellanic Clouds (SMC, LMC) from fitting Spitzer and Herschel observations with the \citet{DL07} dust model. We derive the abundance of the small carbonaceous grain (or polycyclic aromatic hydrocarbon; PAH) component. The global PAH fraction (q_pah, the fraction of the dust mass in the form of PAHs) is smaller in the SMC (1.0$^{+0.3}_{-0.3}$%) than in the LMC (3.3$^{+1.4}_{-1.3}$%). We measure the PAH fraction in different gas phases (H II regions, ionized gas outside of H II regions, molecular gas, and diffuse neutral gas). H II r…
