早型旋涡星系M81(NGC 3031)的形态学解构研究  

Morphological Decomposition of the Early-type Spiral Galaxy M81(NGC 3031)

作　　者：龚俊宇 毛业伟 GONG Jun-yu;MAO Ye-wei(Center for Astrophysics,Guangzhou University,Guangzhou 510006;Department of Astronomy,School of Physics and Materials Science,Guangzhou University,Guangzhou 510006)

机构地区：[1]广州大学天体物理中心,广州510006 [2]广州大学物理与材料科学学院天文系,广州510006

出　　处：《天文学报》2023年第2期82-103,共22页Acta Astronomica Sinica

基　　金：国家自然科学基金项目(U2031106、U2031201)资助。

摘　　要：利用星系解构软件GALFIT通过面亮度轮廓拟合对近邻早型旋涡星系M81 (NGC 3031)进行形态学解构,旨在探究M81星系的结构组成并对其进行形态学量化.通过6种解构模式,对M81进行了不同复杂程度的结构分解,其中最复杂的解构模式包含核球、盘、外旋臂、内旋臂、星系核5个子结构.研究结果显示, M81有一个Sérsic指数约为5.0的经典核球,其形态和光度在不同解构模式中均保持稳定;M81星系盘的Sérsic指数约为1.2,但它的形态参数和光度与是否分解内旋臂相关.不同子结构的组合对作为混合体的星系整体的形态有不可忽视的影响.星系解构的结果提供了不同解构模式适用性的建议:其中核球+盘+星系核的三成分解构适用于大样本星系的核-盘研究;而考虑旋臂的复杂解构则适合于对星系子结构的精确测量,如小样本(或个源)研究.基于Spitzer-The Infrared Array Camera (IRAC) 4.5μm的单波段图像的形态学解构研究是后续一系列研究的开始,在此基础上未来将会对M81进行多波段解构,同时研究不同子结构的光谱能量分布和星族性质,并推断M81各子结构的形成历史和演化过程.This paper presents a morphological investigation of the early-type spiral galaxy M81(NGC 3031)through decomposition by fitting radial profiles of surface brightness using the software GALFIT,aimed at exploring structural components of M81 and quantifying their morphology.In this work,we adopt 6 types of decompositions with different numbers of morphological components,among which the most complicated one contains 5 components such as a bulge,a disk,a pair of outer spiral arms,a pair of inner spiral arms,and a galactic nucleus.The results show that,M81 hosts a classical bulge with the S´ersic index∼5.0;the morphology and the luminosity for the bulge are almost constant in the different decomposition types.The disk of M81 has the S´ersic index∼1.2 but the morphology and the luminosity are found sensitive to the inclusion of the inner spiral arms in the decomposition or not.The results of this work indicate that the combination of individual substructures has a considerable impact on the morphology of the galaxy as a mixture.On the basis of the results,the usability of the different types of decomposition is suggested in this work.The three-component decomposition,i.e.,bulge+disk+nucleus,is applicable to statistics of large samples of galaxies;more complicated decomposition with spiral arms taken into account is suitable for precise measurements of individual galaxies in small samples.This work is based on the single-band Spitzer-The Infrared Array Camera(IRAC)4.5m image.In the future,we will carry out multi-wavelength decomposition,for the purpose of investigating spectral energy distributions and stellar population properties for the galactic substructures,and thereby deduce their formation history and evolution processes.

关 键 词：星系:个别:M81 核球 星系:基本参数:形态学 星系:结构 星系:旋涡 

分 类 号：P157[天文地球—天文学]