ELUCIDATION OF ORIGINS OF STELLAR MASS WITH WIDE FIELD IR SURVEYS: IMF IN STAR FORMATION

本研究旨在建立恒星的初始质量函数（IMF），包括非常低质量的恒星，如褐矮星，甚至行星质量的物体。为此，我们对恒星形成区域进行了广域红外巡天。因为红外巡天可以发现嵌入的星团，它们的质量分布反映了IMF。此外，由于年轻恒星的引力能在红外波段相对较亮，我们可以探测到质量非常低的恒星。我们可以根据它们的颜色和偏振信息来区分年轻恒星和背景恒星。主要成果总结如下：(1)对近地恒星形成区进行了观测。南非的IRSF 1.4米望远镜，夏威夷的斯巴鲁和双子座望远镜。在IRSF的拍摄是使用由NAOJ和Naoya大学开发的SIRIUS jhk波段同步相机进行的。观测到的区域是蛇夫座、Cha、rcra、猎户座、船帆座、天鹅座的分子云。我们已经在一些地区发现了许多新的褐矮星和行星质量候选者。猎户座、S106和船帆区的结果已经发表在相关期刊上。我们已经发现了褐矮星的普遍性，而非常低质量恒星与低质量恒星的相对数量因地区而异。(2)在麦哲伦桥中发现了中等质量的年轻恒星（发表于学术期刊）。(3)研制了IRSF/SIRIUS大视场红外偏振仪，并进行了偏振观测。我们发现了一些新的星周结构。(4)我们对蛇蛇座云核进行了光度测定和光谱分析，找到了质量最低的候选星云。

This research aims to establish the initial mass function (IMF) of stars, including very low-mass stars such as brown dwarfs and even planetary mass objects. In order to this, we have conducted very wide field infrared surveys of star forming regions. Since infrared surveys can uncover the embedded stellar clusters whose mass distribution reflects the IMF. In addition, because the young stars are relatively bright at infrared due to their gravitational energy, we can detect down to very low mass stars. We can distinguish young stars from background stars taking into account their color and polarization information. The mains results are summarized as follows:(1)We conducted observations of nearby star forming regions. with the IRSF 1.4m telescope in South Africa, the Subaru and Gemini telescopes in Hawaii. Those at IRSF were conducted with the SIRIUS JHKs-band simultaneous camera, which was developed by NAOJ and Naoya University. The observed regions are Oph, Cha, R CrA, Orion, Vela, Cygnus molecular clouds. We have detected a number f new brown dwarfs and planetary mass candidates in some regions. The results for Orion, S106, and Vela regions were already published in refereed journals. We have discovered the universality of brown dwarfs and the relative populations of very low mass stars to low mass stars vary from region to region.(2)We discovered the middle mass young stars in the Magellanic Bridge (published in refereed journal).(3)We developed wide field infrared polarimeter for IRSF/SIRIUS and conducted polarization observations. We detected a number of new circumstellar structures.(4)We conducted photometry and spectroscopy of the Oph cloud core and found lowest mass candidates.