Extraplanar Dust in Spiral Galaxies: Tracing Outflows in the Disk-Halo Interface
J. Christopher Howk
备注：
8 pages; Invited review for the proceedings of "The Role of Disk-Halo Interaction in Galaxy Evolution: Outflow vs. Infall?" (Ed. M. de Avillez), in Espinho, Portugal, 18-22 August 2008 ; high resolution version at http://www.nd.edu/~jhowk/Papers/papers.html#conference
There is now ample evidence that the interstellar thick disks of spiral galaxies are dusty. Although the majority of extraplanar gas in the first few kiloparsecs above the plane of a spiral galaxy is matter that has been expelled from the thin disk, the feedback-driven expulsion does not destroy dust grains altogether (and there is not yet any good measure suggesting it changes the dust-to-gas mass ratio). Direct optical imaging of a majority of edge-on spiral galaxies shows large numbers of dusty clouds populating the thick disk to heights z~2 kpc. These observations are likely revealing a cold, dense phase of the thick disk interstellar medium. New observations in the mid-infrared show emission from traditional grains and polycyclic aromatic hydrocarbons (PAHs) in the thick disks of spiral galaxies. PAHs are found to have large scale heights and to arise both in the dense dusty clouds traced through direct optical imaging and in the diffuse ionized gas. In this contribution, we briefly summarize these probes of dust in the thick disks of spiral galaxies. We also argue that not only can dust can be used to trace extraplanar material that has come from within the thick disk, but that its absence can be a marker for newly accreted matter from the circumgalactic or intergalactic medium. Thus, observations of dust can perhaps provide a quantitative measure of the importance of "outflow versus infall" in spiral galaxies.
IllustrisTNG50 angular momentum maps: tracing the morpho-kinematic evolution of galaxies
Aix-Marseille Univ.（艾克斯-马赛大学）；CNRS（法国国家科学研究中心）；CNES（法国国家空间研究中心）；LAM（拉格朗日天体物理实验室）；French-Chilean Laboratory for Astronomy, IRL 3386, CNRS and Universidad de Concepción, Departamento de Astronomía（中智天文联合实验室，智利康塞普西翁大学天文学系）；Universidad de Concepción（智利康塞普西翁大学）；Observatoire Astronomique de Strasbourg, UMR 7550, CNRS, Université de Strasbourg（斯特拉斯堡天文台，斯特拉斯堡大学）
Tracing the Evolution of Ultraluminous Infrared Galaxies into Radio Galaxies with Low Frequency Radio Observations
我们目前的无线电观测超亮红外星系（ULIRGs）使用巨型米波射电望远镜（GMRT），并将它们与档案多频观测，以了解是否ULIRGs是在本地宇宙中的强大的射电大声星系的祖先。超红外类星体的特点是红外线光度大（$L_{IR}>$ 10 $^{12}$ L $\odot$），尘埃质量大（$\sim10^{8}M_{\odot}$），恒星形成活跃（恒星形成速率$\sim$ 10-100 $M_{\odot}~$ yr $^{-1}$）。研究表明，它们代表了富含气体的螺旋星系合并的最后阶段。它们的光度可以归因于星暴活动和活动星系核（AGN）。我们研究了13个ULIRG样本，这些样本通过1.28~GHz的GMRT观测数据光学识别了活动星系核特征。我们的目标是解决任何核心喷流结构或核扩展，从而检查是否ULIRGs正在演变成无线电响亮的椭圆。我们的深，低频观测显示只有一个源的边际扩展。然而，9个ULIRG的综合无线电频谱表现出类似于GPS/CSS/CSO/年轻射电源的特征。估计的光谱年龄为0.4至20百万年，表明它们是年轻的射电源和可能的射电星系的祖先。因此，我们的结论是，虽然大多数ULIRG不显示kpc尺度的扩展无线电发射与核活动，其无线电频谱能量分布确实显示年轻的射电星系的签名。
