A Molecular Gas Study of the Initial and Final Stages of the Ultraluminous Infrared Galaxy Phenomenon

AST-0080881 EVANSU超红外星系（ULIGs）被观测到是密切相互作用/合并的星系。ULIGs中的环核星星形成和活动星系核（AGN）活动都被认为是由分子气体提供燃料的，这两个过程产生的强烈紫外光辐射被尘埃吸收并以红外波长重新发射。光学明亮的类星体可能是ULIG阶段演化的最终产物。 光学上明亮的类星体的出现可能是外流和超新星清除了大部分使类星体核模糊的尘埃后的结果。将进行两个项目，为超低频低重力现象的早期和最后阶段提供潜在的线索。第一个是ULIG祖细胞的分子气体性质的研究。具体而言，正在对ULIGs的一氧化碳（CO）（1到0跃迁）线辐射进行观测调查，这些ULIGs的核仍然相距很远，以确定祖星系的相对分子气体含量。CO数据正在与这些ULIGs的地面和空间光学近红外图像进行比较，以验证分子气体相对于恒星核的位置。对5个ULIGs的初步分析表明，ULIGs的核间距约为5秒差距，温暖的，西弗红外线通量比的ULIGs有CO与活动星系核，而冷，恒星爆发般的流量比的ULIGs有CO与两个核。这样的二分法可能表明，在合并的方式与不同的主要电源成为ultraluminous早期的合并process.The第二个项目是一个样本的类星体的早期ULIG阶段的分子气体残留物的搜索。该样本由17个红外过量类星体组成，被认为代表了严重模糊的ULIGs和经典的光学类星体之间的过渡阶段。样品先前已在光学/近红外波长下成像。这些研究显示了未分辨的明亮核的证据，这些核具有潜在的螺旋臂和潮汐尾，以及明亮的年轻星星团。这些类星体的CO观测将提供统计样本，以便将它们的分子气体性质与ULIG的分子气体性质以及富含气体的最近在CO中发现的高红移ULIGs和类星体。研究结果将帮助天文学家了解星系和类星体之间的差异。这两个项目都将利用欧文斯谷毫米波的观测数据是加州理工学院控制的。 该项目和欧文斯谷毫米阵列由天文科学部提供资金支持。 ***

AST-0080881EVANSUltraluminous infrared galaxies (ULIGs) are observed to be closely interacting/ merging galaxies. Both circumnuclear star formation and active galactic nuclear (AGN) activity in ULIGs are believed to be fueled by molecular gas, and the strong ultraviolet-to-optical radiation generated by both processes is absorbed by dust and re-emitted at infrared wavelengths. Optically bright QSOs may be an evolutionary end product of the ULIG phase. The appearance of optically bright QSOs may be the result after outflows and supernovae have cleared much of the dust responsible for obscuring the QSO nucleus.Two projects will be carried out that will provide potential clues to the early and final stages of ULIG phenomenon. The first is a study of the molecular gas properties of ULIG progenitors. Specifically, an observational survey of the Carbon monoxide (CO) (1 to 0 transition) line radiation of ULIGs, whose nuclei are still widely separated, is being undertaken in order to determine the relative molecular gas content of the progenitor galaxies. The CO data are being compared with ground-based and space-based optical to near-infrared images of these ULIGs to verify the location of the molecular gas relative to the stellar nuclei. Preliminary analysis of five ULIGs with nuclear separations of about 5 parsecs shows that ULIGs with warm, Seyfert-like infrared flux ratios have CO associated with only the AGN, whereas ULIGs with cool, starburst-like flux ratios has CO associated with both nuclei. Such a dichotomy may indicate the manner in which mergers with different primary power sources become ultraluminous early in the merger process.The second project is a search for molecular gas remnants of an early ULIG phase in a sample of QSOs. The sample consists of a family of 17 infrared excess QSOs believed to represent the transition stage between the heavily obscured ULIGs and the classic, optical QSOs. The sample has been previously imaged at optical/near infrared wavelengths. These studies have shown evidence of unresolved bright nuclei with underlying spiral arms and tidal tails, as well as luminous young star clusters. The CO observations of these QSOs will provide the statistical sample needed for a direct comparison of their molecular gas properties to those of ULIGs, as well as to the population of gas-rich, high redshift ULIGs and QSOs recently detected in CO.The results of the research will help astronomers understand the differences between galaxies and QSOs.Both of these projects will make use of observational data taken at the Owens Valley Millimeter Array that is operated by Caltech. This project and the Owens Valley Millimeter Array are supported by funds from the Division of Astronomical Sciences. ***