The most luminous Spitzer point sources in the 30 Doradus triggered second generation are investigated coherently in the 3-8 micron region. Remarkable diversity and complexity in their natures are revealed. Some are also among the brightest JHK sources, while others are not. Several of them are multiple when examined at higher angular resolutions with HST NICMOS and WFPC2/WFC3 as available, or with VISTA/VMC otherwise. One is a dusty compact H II region near the far northwestern edge of the complex, containing a half dozen bright I-band sources. Three others appear closely associated with luminous WN stars and causal connections are suggested. Some are in the heads of dust pillars oriented toward R136, as previously discussed from the NICMOS data. One resides in a compact cluster of much fainter sources, while another appears monolithic at the highest resolutions. Surprisingly, one is the brighter of the two extended "mystery spots" associated with Knot 2 of Walborn et al. Masses are derived from YSO models for unresolved sources and lie in the 10-30 M_{sun} range. Further analysis of the IR sources in this unique region will advance understanding of triggered massive star formation, perhaps in some unexpected and unprecedented ways.
Spitzer View of Young Massive Stars in the LMC HII Complex N44
大麦云星云(LMC)中的HII复合体N44提供了一个很好的地点来详细研究温和星暴中的恒星形成,因为它拥有三个处于不同演化阶段的恒星形成区域,并且它不像剑鱼座30巨大的HII区域那样复杂和混乱。我们已经获得了斯皮策太空望远镜的观测和补充的地面4 m uBVIJK观测N44,以确定候选的大质量年轻恒星物体(YSO)。我们进一步分类的YSO类型I,II和III,根据他们的光谱能量分布(SED)。在我们的60个YSO候选样本中,其中约65%在高分辨率地基图像中被分解为多个分量或扩展源。我们模拟了36个YSO的SED,这些YSO在一个组中表现为单一或占主导地位。我们发现I型和I/II型YSO很好地拟合,但II型和II/III型YSO显示出它们观察到的SED和不包括PAH排放的模型之间的偏差。我们还发现,一些III型YSO在其盘组件中具有中心孔。在四个超紧凑的HII区发现了YSO对应物,它们的恒星质量由SED模型拟合确定,与由HII区电离要求估计的结果吻合得很好。的YSO的分布进行了比较的基础恒星星族和星际气体的条件,以说明目前形成的O型恒星和以前形成的大质量恒星之间的相关性。也提出了触发恒星形成的证据。
The Spitzer Space Telescope Survey of the Orion A & B Molecular Clouds - Part I: A Census of Dusty Young Stellar Objects and a Study of their Mid-IR Variability
We present the results from Chandra X-ray observations, and near- and mid-infrared analysis, using VISTA/VVV and Spitzer/GLIMPSE catalogs, of the high-mass star-forming region IRAS 16562-3959, which contains a candidate for a high mass protostar. We detected 249 X-ray sources within the ACIS-I field-of-view. The majority of the X-ray sources have low count rates (< 0.638 cts/ks), and hard X-ray spectra. The search for YSOs in the region using VISTA/VVV and Spitzer/GLIMPSE catalogs resulted in a total of 799 YSOs, with 66 Class I and 733 Class II YSOs. The search for near- and mid-infrared coun…
In this paper we undertake a study of the 21 square degree SMOG field, a Spitzer cryogenic mission Legacy program to map a region of the outer Milky Way towards the Perseus and Outer spiral arms with the IRAC and MIPS instruments. We identify 4648 YSOs across the field. Using the DBSCAN method we identify 68 clusters or aggregations of YSOs in the region, having 8 or more members. We identify 1197 class Is, 2632 class IIs, 819 class IIIs, of which 45 are candidate transition disk objects, utilizing the MIPS 24 photometry. The ratio of YSOs identified as members of clusters was 2872/4648, or 62…
Tracing star formation across the Rosette nebula using deep Spitzer imaging
University of St Andrews(圣安德鲁斯大学);Universidade de Lisboa(里斯本大学);Univ. Bordeaux(波尔多大学);European Southern Observatory(欧洲南方天文台);Istituto Nazionale di Astrofisica (INAF) – Osservatorio Astronomico di Palermo(意大利国家天体物理研究所(INAF)- 巴勒莫天文台)
We present ~120,000 Spitzer/IRAC candidate young stellar objects (YSOs) based on surveys of the Galactic midplane between l~255 deg and 110 deg, including the GLIMPSE I, II, and 3D, Vela-Carina, Cygnus X, and SMOG surveys (613 square degrees), augmented by near-infrared catalogs. We employed a classification scheme that uses the flexibility of a tailored statistical learning method and curated YSO datasets to take full advantage of IRAC's spatial resolution and sensitivity in the mid-infrared ~3-9 micron range. Multi-wavelength color/magnitude distributions provide intuition about how the clas…
Observed Young Stellar Objects (YSOs) are used to study star formation and characterize star forming regions. For this purpose, YSO candidate catalogs are compiled from various surveys, especially in the infrared (IR), and simple selection schemes in colour-magnitude diagrams (CMDs) are often used to identify and classify YSOs. We propose a methodology for YSO classification through Machine Learning (ML) using Spitzer IR data. We detail our approach in order to ensure reproducibility and provide an in-depth example on how to efficiently apply ML to an astrophysical classification. We used feed…
The Spitzer Space Telescope Survey of the Orion A and B Molecular Clouds II: the Spatial Distribution and Demographics of Dusty Young Stellar Objects
我们分析了空间分布的尘埃年轻恒星物体(YSO)中确定的斯皮策调查的猎户座分子云,增强这些数据与钱德拉X射线观测,以纠正密集的集群区域的不完整性。我们还设计了一个计划,以纠正空间变化的不完整性时,X射线数据不可用。YSO的局部表面密度从1 pc $^{-2}$到超过10,000 pc $^{-2}$不等,原恒星往往位于更高密度的区域。这个密度范围类似于其他被调查的有团簇的分子云,但比没有团簇的云更宽。通过识别表面密度为$\ge10$ pc $^{-2}$的连续区域的集群和组,我们发现,59%的YSO是在最大的集群,猎户座星云集群(ONC),而13%的YSO被发现在一个分布式的人口。在分布的星群中,原恒星的比例较低,这证明它比星群和星团要古老一些。团簇和基团的结构性质的检查表明,团簇的峰值表面密度与成员的数量近似线性增加。此外,所有超过70个成员的簇都表现出不对称和/或高度伸长的结构。ONC在0.1 pc的内部变得方位对称,这表明该星团的年龄只有$\sim 2$ Myr。我们发现猎户座B星云的恒星形成效率(SFE)异常低,并且单个星系团和星系团的SFE比猎户座B星云高一个数量级。最后,我们讨论了年轻的低质量恒星在猎户座云和猎户座OB 1协会之间的关系,我们确定上限的磁盘可能会受到影响的紫外线辐射从OB星或在密集的,集群区域的动态相互作用的分数。
We present an observational study of small-scale feedback processes operating in the star-forming region located in the wall of the expanding supershell around the Cyg OB1 association. The interstellar gas and dust content and pre-stellar populations in the vicinity of the open star cluster vdB 130 are analysed based on new optical and IR observations performed with the 6-m (3D spectroscopic mapping in the [SII] doublet) and 2.5-m (optical and NIR images) Russian telescopes along with the archival data of Spitzer and Herschel space telescopes. Analysing ionized gas kinematics and emission spec…
Active star forming regions are excellent laboratories for studying the origins and evolution of young stellar object (YSO) clustering. The W40 - Serpens South region is such a region, and we compile a super near-and-mid-infrared catalog of point sources in it, based on deep NIR observations of CFHT in combination with 2MASS, UKIDSS, and Spitzer catalogs. From this catalog, we identify 832 YSOs, and classify 15, 135, 647, and 35 of them to be the deeply embedded sources, Class I, Class II YSOs, and transition disk sources, respectively. In general, these YSOs are well correlated with the filam…
OB associations are home to newly formed massive stars, whose turbulent winds and ionizing flux create H II regions rich with star formation. Studying the distribution and abundance of young stellar objects (YSOs) in these ionized bubbles can provide essential insight into the physical processes that shape their formation, allowing us to test competing models of star formation. In this work, we examined one such OB association, Cepheus OB4 (Cep OB4) - a well-suited region for studying YSOs due to its Galactic location, proximity, and geometry. We created a photometric catalog from Spitzer/IRAC…
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…
We present a comprehensive study of massive young stellar objects (YSOs) in the metal-poor galaxy NGC 6822 using IRAC and MIPS data obtained from the {\em Spitzer Space Telescope}. We find over 500 new YSO candidates in seven massive star-formation regions; these sources were selected using six colour-magnitude cuts. Via spectral energy distribution fitting to the data with YSO radiative transfer models we refine this list, identifying 105 high-confidence and 88 medium-confidence YSO candidates. For these sources we constrain their evolutionary state and estimate their physical properties. The…
Extensive surveys of star-forming regions with Spitzer have revealed populations of disk-bearing young stellar objects. These have provided crucial constraints, such as the timescale of dispersal of protoplanetary disks, obtained by carefully combining infrared data with spectroscopic or X-ray data. While observations in various regions agree with the general trend of decreasing disk fraction with age, the Lupus V and VI regions appeared to have been at odds, having an extremely low disk fraction. Here we show, using the recent Gaia data release 2 (DR2), that these extremely low disk fractions…
(abridged) Star formation in the outer Galaxy, i.e., outside of the Solar circle, has been lightly studied in part due to low CO brightness of molecular clouds linked with the negative metallicity gradient. Recent infrared surveys provide an overview of dust emission in large sections of the Galaxy, but suffer from cloud confusion and poor spatial resolution at far-infrared wavelengths. We aim to develop a methodology to identify and classify young stellar objects (YSOs) in star-forming regions in the outer Galaxy, and use it to solve a long-standing confusion with the distance and evolutionar…
Most stars born in clusters and recent results suggest that star formation (SF) preferentially occurs in subclusters. Studying the morphology and SF history of young clusters is crucial to understanding early SF. We identify the embedded clusters of young stellar objects (YSOs) down to M stars, in the HII regions RCW33, RCW32 and RCW27 of the Vela Molecular Ridge. Our aim is to characterise their properties, such as morphology and extent of the clusters in the three HII regions, derive stellar ages and the connection of the SF history with the environment. Through public photometric surveys su…