HIGH- AND INTERMEDIATE-MASS YOUNG STELLAR OBJECTS IN THE LARGE MAGELLANIC CLOUD
HIGH- AND INTERMEDIATE-MASS YOUNG STELLAR OBJECTS IN THE LARGE MAGELLANIC CLOUD
复制标题
大麦哲伦星云中的高质量和中等质量年轻恒星天体
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
Y. Chu
中科院分区：
文献类型：
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作者：
R. Gruendl;Y. Chu
档案斯皮策红外阵列相机 (IRAC) 和大麦哲伦星云 (LMC) 的 MIPS 观测已被用来寻找年轻恒星物体 (YSO)。我们对这些数据进行了独立的孔径光度测量，并将不同通带的结果合并以生成光度测量目录。为了验证我们的方法，我们还分析了 SAGE 和 SIRE Legacy 项目的数据；我们的光度测量结果与这些程序发布的光度测量结果基本一致。对 LMC 光度目录的详细完整性分析表明，在 3.6、4.5、5.8、8.0 和 24 μm 处，90% 完整性限制平均分别为 16.0、15.0、14.3、13.1 和 9.2 mag。使用我们的中红外光度目录和两个简单的选择标准，[4.5]−[8.0]>2.0 排除正常和演化恒星，[8.0]>14−([4.5]−[8.0]) 排除背景星系，我们已经确定了 LMC 中可能是 YSO 的 2910 个源的样本。然后，我们使用斯皮策观测结果并辅以光学和近红外数据来仔细评估每个源的性质。为此，我们同时考虑多波长图像和光度测定来评估源形态、从光学到中红外波长的光谱能量分布 (SED) 以及周围的星际环境，以确定每个源最可能的性质。根据对初始样本的检查，我们认为 1172 个源极有可能是 YSO。我们还确定了 1075 个可能的背景星系，与太古调查估计的预期数量一致。 Spitzer IRS 对我们样本中 269 个最亮的 YSO 的观测证实，≳95% 确实是 YSO。对颜色-颜色和颜色-星等图的检查显示，颜色-星等空间中没有简单的标准可以明确地将 LMC YSO 与所有渐近巨星分支 (AGB)/后 AGB 恒星、行星状星云和背景星系分开。 SAGE 团队还对 LMC 中的 YSO 进行了全面的搜索，并由 Whitney 等人报告。这两个搜索之间存在三个主要区别。 (1) 在颜色-星等空间的共同区域中，我们的 1172 个可能的 YSO 中约有 850 个在 SAGE YSO 目录中被遗漏，因为它们保守的点源识别标准排除了叠加在复杂恒星和星际环境上的 YSO。 (2) SAGE 团队识别出的 YSO 中约有 20%–30% 是我们归类为背景星系的来源。 (3) SAGE YSO 目录在我们排除的部分颜色-幅度空间中识别出 YSO，因此包含我们分析中遗漏的更进化或更暗的 YSO。在对 LMC 中的恒星形成进行统计研究之前，应考虑这两个 YSO 星表的缺点和优点。最后，LMC中最有可能的YSO候选者的IRAC波段的中红外光度函数可以用N(L) ∝ L−1很好地描述，如果采用L ∝ M2.4的质量-光度关系，这与Salpeter初始质量函数一致。
Archival Spitzer Infrared Array Camera (IRAC) and MIPS observations of the Large Magellanic Cloud (LMC) have been used to search for young stellar objects (YSOs). We have carried out independent aperture photometry of these data and merged the results from different passbands to produce a photometric catalog. To verify our methodology we have also analyzed the data from the SAGE and SWIRE Legacy programs; our photometric measurements are in general agreement with the photometry released by these programs. A detailed completeness analysis for our photometric catalog of the LMC shows that the 90% completeness limits are, on average, 16.0, 15.0, 14.3, 13.1, and 9.2 mag at 3.6, 4.5, 5.8, 8.0, and 24 μm, respectively. Using our mid-infrared photometric catalogs and two simple selection criteria, [4.5]−[8.0]>2.0 to exclude normal and evolved stars and [8.0]>14−([4.5]−[8.0]) to exclude background galaxies, we have identified a sample of 2910 sources in the LMC that could potentially be YSOs. We then used the Spitzer observations complemented by optical and near-infrared data to carefully assess the nature of each source. To do so we simultaneously considered multiwavelength images and photometry to assess the source morphology, spectral energy distribution (SED) from the optical through the mid-infrared wavelengths, and the surrounding interstellar environment to determine the most likely nature of each source. From this examination of the initial sample, we suggest that 1172 sources are most likely YSOs. We have also identified 1075 probable background galaxies, consistent with the expected number estimated from the SWIRE survey. Spitzer IRS observations of 269 of the brightest YSOs from our sample have confirmed that ≳95% are indeed YSOs. An examination of color–color and color–magnitude diagrams shows no simple criteria in color–magnitude space that can unambiguously separate the LMC YSOs from all asymptotic giant branch (AGB)/post-AGB stars, planetary nebulae, and background galaxies. A comprehensive search for YSOs in the LMC has also been carried out by the SAGE team and reported by Whitney et al. There are three major differences between these two searches. (1) In the common region of color–magnitude space, ∼850 of our 1172 probable YSOs are missed in the SAGE YSO catalog because their conservative point-source identification criteria have excluded YSOs superposed on complex stellar and interstellar environments. (2) About 20%–30% of the YSOs identified by the SAGE team are sources we classify as background galaxies. (3) The SAGE YSO catalog identifies YSO in parts of color–magnitude space that we excluded and thus contains more evolved or fainter YSOs missed by our analysis. The shortcomings and strengths of both these YSO catalogs should be considered prior to statistical studies of star formation in the LMC. Finally, the mid-infrared luminosity functions in the IRAC bands of our most likely YSO candidates in the LMC can be well described by N(L) ∝ L−1, which is consistent with the Salpeter initial mass function if a mass–luminosity relation of L ∝ M2.4 is adopted.
DOI：
10.1088/0004-6256/136/3/919
发表时间：
2005-06
期刊：
The Astronomical Journal
影响因子：
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作者：
M. Meixner;K. Gordon;R. Indebetouw;J. Hora;B. Whitney;R. Blum;W. Reach;J. Bernard;M. Meade;B. Babler;C. Engelbracht;B. For;K. Misselt;U. Vijh;C. Leitherer;M. Cohen;E. Churchwell;F. Boulanger;J. Frogel;Y. Fukui;J. Gallagher;V. Gorjian;J. Harris;D. Kelly;A. Kawamura;Soyoung Kim;W. Latter;S. Madden;Ciska Markwick-Kemper;A. Mizuno;N. Mizuno;J. Mould;A. Nota;M. Oey;K. Olsen;T. Onishi;R. Paladini;N. Panagia;P. Pérez-González;H. Shibai;Sato Shuji;Linda J. Smith;L. Staveley-Smith;A. Tielens;T. Ueta;S. V. Dyk;K. Volk;M. Werner;D. Zaritsky
通讯作者：
M. Meixner;K. Gordon;R. Indebetouw;J. Hora;B. Whitney;R. Blum;W. Reach;J. Bernard;M. Meade;B. Babler;C. Engelbracht;B. For;K. Misselt;U. Vijh;C. Leitherer;M. Cohen;E. Churchwell;F. Boulanger;J. Frogel;Y. Fukui;J. Gallagher;V. Gorjian;J. Harris;D. Kelly;A. Kawamura;Soyoung Kim;W. Latter;S. Madden;Ciska Markwick-Kemper;A. Mizuno;N. Mizuno;J. Mould;A. Nota;M. Oey;K. Olsen;T. Onishi;R. Paladini;N. Panagia;P. Pérez-González;H. Shibai;Sato Shuji;Linda J. Smith;L. Staveley-Smith;A. Tielens;T. Ueta;S. V. Dyk;K. Volk;M. Werner;D. Zaritsky