[论文解读] Physics of ULIRGs with MUSE and ALMA: The PUMA project

Michele Perna, Santiago Arribas+9 more|arXiv (Cornell University)|Nov 19, 2020

Galaxies: Formation, Evolution, Phenomena参考文献 135被引用 3

一句话总结

本研究展示了PUMA项目首项成果，该项目利用MUSE积分场光谱和ALMA干涉测量，对25个邻近超亮红外星系（ULIRGs）进行了多波段观测。结果表明，[O III]和Na ID的宽幅不对称发射线——指示高速喷流——在ULIRG核区普遍存在，其中85%的案例中，气体速度弥散度比恒星速度弥散度高出超过0.15 dex，强烈表明在并合阶段普遍存在由活动星系核（AGN）和星暴驱动的风。”,

ABSTRACT

Context. Ultraluminous infrared galaxies (ULIRGs) are characterised by extreme starburst (SB) and active galactic nucleus (AGN) activity, and are therefore ideal laboratories for studying the outflow phenomena and their feedback effects. We have recently started a project called Physics of ULIRGs with MUSE and ALMA (PUMA), which is a survey of 25 nearby ( z < 0.165) ULIRGs observed with the integral field spectrograph MUSE and the interferometer ALMA. This sample includes systems with both AGN and SB nuclear activity in the pre- and post-coalescence phases of major mergers. Aims. The main goals of the project are (i) to study the prevalence of (ionised, neutral, and molecular) outflows as a function of the galaxy properties, (ii) to constrain the driving mechanisms of the outflows (e.g. distinguish between SB and AGN winds), and (iii) to identify and characterise feedback effects on the host galaxy. In this first paper, we present details on the sample selection, MUSE observations, and data reduction, and derive first high-level data products. Methods. MUSE data cubes were analysed to study the dynamical status of each of the 21 ULIRGs observed so far, taking the stellar kinematics and the morphological properties inferred from MUSE narrow-band images into account. We also located the ULIRG nuclei, taking advantage of near-infrared (HST) and millimeter (ALMA) data, and studied their optical spectra to infer (i) the ionisation state through standard optical line ratio diagnostics, and (ii) outflows in both atomic ionised ([O III], H α ) and neutral (Na ID) gas. Results. We show that the morphological and stellar kinematic classifications are consistent: post-coalescence systems are more likely associated with ordered motions, while interacting (binary) systems are dominated by non-ordered and streaming motions. We also find broad and asymmetric [O III] and Na ID profiles in almost all nuclear spectra, with line widths in the range [300 − 2000] km s −1 , possibly associated with AGN- and SB-driven winds. This result reinforces previous findings that indicated that outflows are ubiquitous during the pre- and post-coalescence phases of major mergers.

研究动机与目标

• 研究电离、中性及分子喷流在ULIRGs中的普遍性及其与星系性质的关系。
• 在主要并合系统中区分活动星系核（AGN）驱动与星暴驱动的喷流机制。
• 表征并合前后阶段宿主星系中反馈效应的影响。
• 利用MUSE和ALMA数据建立高分辨率、多相态的星际介质（ISM）动力学图景。
• 通过BPT诊断图和高光谱分辨率数据，改进对ULIRG核区电离机制的分类。

提出的方法

• 对21个ULIRGs（z < 0.165）进行深度MUSE积分场光谱观测，以获得空间分辨的恒星与电离气体动力学特性。
• 应用pPXF恒星群体合成方法，从MUSE数据立方中提取恒星速度弥散度和动力学结构。
• 利用MUSE的窄带成像对形态和动力学状态（如有序旋转与流体运动）进行分类。
• 从ALMA和HST识别的核区提取31个核谱，通过BPT诊断图和线轮廓不对称性研究电离状态。
• 测量[O III]和Na ID线的速度弥散度，并与恒星速度弥散度（σ*）比较，以识别非引力运动。
• 结合MUSE与ALMA数据，交叉识别喷流并评估其在并合序列不同阶段的物理驱动机制。

实验结果

研究问题

• RQ1 ULIRGs的运动学特性（如有序运动与流体运动）与其并合阶段（并合前或并合后）之间有何关联？
• RQ2 电离气体和中性气体喷流在ULIRG核区的普遍存在程度如何？其中多大比例由AGN驱动，多大比例由星暴驱动？
• RQ3 发射线中的速度弥散度与恒星速度弥散度之间的关系是什么？这对星际介质动力学有何启示？
• RQ4 将BPT诊断图应用于高分辨率MUSE光谱，与基于长缝光谱数据的文献分类相比有何异同？
• RQ5 在主要并合阶段，喷流在调节ULIRGs中的恒星形成与反馈过程中的作用是什么？

主要发现

• 并合后的ULIRGs表现出有序的盘状恒星动力学，而相互作用（双星）系统则呈现非有序和流体运动特征。
• 在11个并合系统中，8个显示有序旋转模式；在10个相互作用系统中，7个表现出非有序动力学。
• 全部31个核谱均显示[O III]和Na ID发射线具有不对称性和展宽，速度宽度达300–2000 km/s。
• 在85%的核谱中，电离气体和中性气体的速度弥散度比恒星速度弥散度（σ*）高出超过0.15 dex，表明存在强烈的非引力运动。
• BPT诊断将11个核区分类为以恒星形成为主，9个为AGN主导，6个为LINER样；5个核区诊断结果不一致，提示存在混合电离机制。
• 在高AGN成分系统（αAGN > 0.5）中，中性喷流（Na ID）极为罕见，仅一个此类核区检测到可分辨喷流，凸显在AGN主导环境中观测的挑战。