The aim of this study is to constrain the dynamics, structure and feeding of the compact nucleous of NGC4418, and to reveal the nature of the main hidden power source: starburst or AGN. We obtained high spatial resolution observations of NGC4418 at 1.4 and 5 GHz with MERLIN, and at 230 and 270 GHz with the SMA very extended configuration. We use the continuum morphology and flux density to estimate the size of the emitting region, the star formation rate and the dust temperature. Emission lines are used to study the kinematics through position-velocity diagrams. Molecular emission is studied with population diagrams and by fitting an LTE synthetic spectrum. We detect bright 1mm line emission from CO, HC3N, HNC and C34S, and 1.4 GHz absorption from HI. The CO 2-1 emission and HI absorption can be fit by two velocity components at 2090 and 2180 km s-1. We detect vibrationally excited HC3N and HNC, with Tvib 300K. Molecular excitation is consistent with a layered temperature structure, with three main components at 80, 160 and 300 K. For the hot component we estimate a source size of less than 5 pc. The nuclear molecular gas surface density of 1e4 Msun pc-2 is extremely high, and similar to that found in the ultra-luminous infrared galaxy (ULIRG) Arp220. Our observations confirm the the presence of a molecular and atomic in-flow, previously suggested by Herschel observations, which is feeding the activity in the center of NGC4418. Molecular excitation confirms the presence of a very compact, hot dusty core. If a starburst is responsible for the observed IR flux, this has to be at least as extreme as the one in Arp220, with an age of 3-10 Myr and a star formation rate >10 Msun yr-1. If an AGN is present, it must be extremely Compton-thick.
Direct VLBI evidence for a buried AGN in the triple-merger LIRG UGC 2369S
Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences（孔科利天文台，HUN-REN 天文学与地球科学研究中心）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）；Xinjiang Astronomical Observatory, Chinese Academy of Sciences（中国科学院新疆天文台）；Department of Astronomy, Institute of Physics and Astronomy, ELTE Eötvös Loránd University（罗兰大学物理与天文学研究所天文学系）；HUN-REN–ELTE Extragalactic Astrophysics Research Group, ELTE Eötvös Loránd University（HUN-REN–罗兰大学河外天体物理学研究组）
Probing Heavily Obscured AGN in Major Galaxy Mergers Using the mm-X-ray Correlation
Pontificia Universidad Católica de Chile（智利天主教 Pontificia 大学）；Universidad de Tarapacá（塔拉帕卡大学）；National Radio Astronomy Observatory（美国国家射电天文台）；University of Virginia（弗吉尼亚大学）；Osaka University（大阪大学）；RIKEN Cluster for Pioneering Research（理化学研究所先锋研究集群）；Clemson University（克莱姆森大学）
Multiphase Analysis of (U)LIRG Nuclear Activity (MAUNA). I. Spatially Resolved Optical Emission-Line Diagnostics
California Institute of Technology（加州理工学院）；University of California, Irvine（加州大学尔湾分校）；Instituto de Astrofísica de Canarias（加那利天体物理研究所）；Universidad de La Laguna（拉帕鲁纳大学）
The Starburst-AGN connection: quenching the fire and feeding the beast
两个旋涡星系的合并被认为是产生椭圆星系和早型星系的主要途径之一。在这个过程中，该系统变成了一个（超）亮红外星系，或（U）LIRG，它会演变成类星体，K+A星系，最后变成早期星系。这一变化的时间尺度仅受观测的松散约束。特别地，K+A阶段应该紧随类星体阶段之后，在此期间，（U）LIRG阶段剩余的尘埃和气体被AGN排出。具有K+A光谱特征的类星体的中间类别，星暴后类星体或PSQ，可能代表类星体和K+ A之间的过渡阶段。我们从SDSS DR 7类星体目录中收集了72个$z<0.5$ PSQ样本。我们发现，在这个样本中的中间年龄人口平均显着较弱，比他们的假定的后代，K+A星系的金属贫乏。PSQ的典型的光谱能量分布是很好地拟合由三个组件：星光;一个模糊的幂律;和一个热的尘埃组件所需的重现中红外通量。从斜率和测辐射热光度的幂律分量，我们估计典型的质量和吸积率的活动星系核，但我们发现在我们的样品中的强大的无线电大声或强X射线发射器的证据很少。这可能表明，幂律成分起源于核恒星暴，而不是活动星系核，如果它们的大部分年轻恒星仍在形成，或者活动星系核仍然被尘埃和气体严重笼罩。我们发现，这两种选择都是有问题的，需要更多更好的光学，X射线和毫米波观测来阐明PSQ的进化历史。
