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arXiv 1809.04788astro-ph.GA
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早期合并中的分子气体和恒星形成性质:SMA CO(2-1)LIRGs NGC 3110和NGC 232的观测

Molecular gas and Star Formation Properties in Early Stage Mergers: SMA CO(2-1) Observations of the LIRGs NGC 3110 and NGC 232

D. Espada, S. Martin, S. Verley, A. R. Pettitt, S. Matsushita, M. Argudo-Fernandez, Z. Randriamanakoto, P. -Y. Hsieh, T. Saito, R. E. Miura, Y. Kawana, J. Sabat… 展开作者

D. Espada, S. Martin, S. Verley, A. R. Pettitt, S. Matsushita, M. Argudo-Fernandez, Z. Randriamanakoto, P. -Y. Hsieh, T. Saito, R. E. Miura, Y. Kawana, J. Sabater, L. Verdes-Montenegro, P. T. P. Ho, R. Kawabe, D. Iono

摘要:

星系的合并是星系演化的一个重要模式,因为它们可以有效地触发强大的星暴。然而,在其早期阶段的分子气体性质的观测研究是稀缺的。本文给出了用亚毫米波阵列(SMA)获得的两个亮红外星系(NGC 3110和NGC 232)的CO(2-1)干涉图,分辨率约为1 kpc。虽然NGC 3110是一个与次要(14:1恒星质量)伴星相互作用的螺旋星系,但NGC 232正在与一个类似大小的物体相互作用。我们发现,这种相互作用可能会导致在这些星系中的分子气体含量和中心浓度的增强,部分以牺牲原子气体。得到的分子气体表面密度在其环核区域是$Σ_{\rm mol}~\gtrsim10^{2.5}$ M $_\odot$ pc $^{-2}$,高于非相互作用的对象的数量级。气体耗尽时间~ 0.5 - 1 Gyr的不同区域,躺在之间的非相互作用盘星系和星暴序列。在NGC 3110的情况下,如果我们假设类似的H $_2$ -CO转换因子,则螺旋臂的耗尽时间比环核区域平均短0.5 dex。我们发现,即使在早期阶段的相互作用与一个小的同伴,星暴形成沿环核区域和旋臂,在那里发现了大量的SSC(~350),并在同一时间,一个大的中央气体浓度正在建立这可能是燃料的活动星系核。NGC 3110系统的主要形态学特性通过我们的数值模拟再现,并使我们能够估计当前的相互作用时代是在最近的方法后约1.5亿年。

英文摘要:

Mergers of galaxies are an important mode for galaxy evolution because they serve as an efficient trigger of powerful starbursts. However, observational studies of the molecular gas properties during their early stages are scarce. We present interferometric CO(2-1) maps of two luminous infrared galaxies (LIRGs), NGC 3110 and NGC 232, obtained with the Submillimeter Array (SMA) with ~ 1 kpc resolution. While NGC 3110 is a spiral galaxy interacting with a minor (14:1 stellar mass) companion, NGC 232 is interacting with a similarly sized object. We find that such interactions have likely induced in these galaxies enhancements in the molecular gas content and central concentrations, partly at the expense of atomic gas. The obtained molecular gas surface densities in their circumnuclear regions are $Σ_{\rm mol}~\gtrsim10^{2.5}$ M$_\odot$ pc$^{-2}$, higher than in non-interacting objects by an order of magnitude. Gas depletion times of ~ 0.5 - 1 Gyr are found for the different regions, lying in between non-interacting disk galaxies and the starburst sequence. In the case of NGC 3110, the spiral arms show on average 0.5 dex shorter depletion times than in the circumnuclear regions if we assume a similar H$_2$-CO conversion factor. We show that even in the early stages of the interaction with a minor companion, a starburst is formed along the circumnuclear region and spiral arms, where a large population of SSCs is found (~350), and at the same time a large central gas concentration is building up which might be the fuel for an active galactic nucleus. The main morphological properties of the NGC 3110 system are reproduced by our numerical simulations and allow us to estimate that the current epoch of the interaction is at ~ 150 Myrs after closest approach.

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