High Resolution Mid-Infrared Imaging of Seyfert Nuclei: Testing the Evolutionary Hypothesis

人们普遍认为，活动星系核（AGN）的“中央引擎”的能量来源来自超大质量黑洞（SMBH）上气体和尘埃的吸积。所谓的“统一方案”认为，由中央发动机产生的无特征连续体被一个几何和光学厚度的材料环面所覆盖，使中央发动机在某些视线范围内变得模糊。统一模型表明，多个类别的AGN不是由不同的物理特性产生的，而是由不同的中央引擎视线产生的，揭示了导致现有分类方案的不同物理条件。然而，最近对塞弗特1型和2型星系的调查表明，AGN的分类仅仅取决于与中央引擎的视线，这一观点受到了质疑。这些调查表明，与Sy-1相比，Sy-2宿主星系通常具有更高的恒星形成水平。一种假设是，塞弗特中央发动机随着时间的推移从Sy-2进化到Sy-1。该理论的一个关键预测是，Seyfert星系在从Sy-2到Sy-1的演化过程中，中心恒星形成和/或温暖尘埃的数量将会减少。为了验证这一理论，将使用位于夏威夷和智利的双双子座8米级望远镜观测中红外波段的各种塞弗特的无偏样本。

PROPOSAL NO: AST 0206617PI: Pina, R KIt is widely accepted that the power source in the 'central engine' of active galactic nuclei (AGN) arises from accretion of gas and dust onto a super massive black hole (SMBH). So-called "Unified Schemes" hold that the featureless continuum produced by the central engine is shrouded in a geometrically and optically thick torus of material, obscuring the central engine from some lines-of-sight. Unified models suggest that multiple classes of AGN result not from different physical characteristics, but rather arise from different lines-of-sight to the central engine, revealing varied physical conditions leading to the existing classification scheme. However, the idea that AGN classification depends solely on the line-of-sight to the central engine has been called into question by recent surveys of Seyfert (Sy) Types 1 and 2 galaxies. These surveys reveal that Sy-2 host galaxies typically have an increased level of star formation as compared to Sy-1. One hypothesis is that Seyfert central engines evolve over time from a Sy-2 to Sy-1. A key prediction of this theory is that Seyfert galaxies will display a decreasing amount of central star formation and/or warm dust throughout the evolution from Sy-2 to Sy-1. In order to test this theory an unbiased sample of various Seyfert in the mid-IR will be observed using the twin Gemini 8-meter class telescopes located in Hawaii and Chile.