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arXiv 1302.4477astro-ph.CO
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近红外发光镓的中红外性质I:GOALS样品的Spitzer IRS光谱

Mid-Infrared Properties of Nearby Luminous Infrared Galaxies I: Spitzer IRS Spectra for the GOALS Sample

S. Stierwalt, L. Armus, J. A. Surace, H. Inami, A. O. Petric, T. Diaz-Santos, S. Haan, V. Charmandaris, J. Howell, D. C. Kim, J. Marshall, J. M. Mazzarella, H. … 展开作者

S. Stierwalt, L. Armus, J. A. Surace, H. Inami, A. O. Petric, T. Diaz-Santos, S. Haan, V. Charmandaris, J. Howell, D. C. Kim, J. Marshall, J. M. Mazzarella, H. W. W. Spoon, S. Veilleux, A. Evans, D. B. Sanders, P. Appleton, G. Bothun, C. R. Bridge, B. Chan, D. Frayer, K. Iwasawa, L. J. Kewley, S. Lord, B. F. Madore, J. E. Melbourne, E. J. Murphy, J. A. Rich, B. Schulz, E. Sturm, V. U, T. Vavilkin, K. Xu

摘要:

大天文台全天LIRG巡天(GOALS)是对本地宇宙中的亮红外星系(LIRGs)进行的多波长研究。在这里,我们提出了低分辨率的斯皮策光谱覆盖5- 38微米,并提供了一个基本的分析附近的LIRGs的中红外光谱特性。在配套文件中,我们讨论了详细的适合的光谱。GOALS样本的244个原子核在180个发光和22个超亮红外星系代表了一个完整的子集的IRAS RBGS,并涵盖了一系列的合并阶段,形态和光谱类型。大多数(>60%)的GOALS LIRG具有高的6.2um PAH等效宽度(EQW > 0.4um)和低水平的硅酸盐吸收(s_9.7um >-1.0)。在U/LIRG中,硅酸盐深度和MIR斜率随LIR增加而增加。U/LIRGs在合并的后期也有平均更陡峭的MIR斜率和更高水平的尘埃遮蔽。这些趋势共同表明,随着气体和尘埃向合并的中心汇集,原子核变得更加紧凑和模糊。偏离这些相关性的源具有非常低的PAH EQW(EQW <0.1 μ m),这与它们的MIR发射由活动星系核主导一致。最严重的尘埃遮蔽源是最紧凑的,在他们的MIR发射,这表明模糊(冷)的尘埃是与外部地区的星暴。随着合并的进展,高EQW(恒星形成主导)源的比例显着下降,而复合源的比例增加,但活动星系核主导源的比例仍然很低。与z~2处的亚毫米星系(SMG)的MIR谱相比,GOALSLIRG在9.7 μ m处有更多的吸收,并有更多的PAH发射。然而,当活动星系核对本地LIRG和高z SMG的贡献被移除时,平均本地星暴LIRG非常类似于星暴SMG。

英文摘要:

The Great Observatories All-Sky LIRG Survey (GOALS) is a multiwavelength study of luminous infrared galaxies (LIRGs) in the local universe. Here we present low resolution Spitzer spectra covering 5-38um and provide a basic analysis of the mid-IR spectral properties for nearby LIRGs. In a companion paper, we discuss detailed fits to the spectra. The GOALS sample of 244 nuclei in 180 luminous and 22 ultraluminous IR galaxies represents a complete subset of the IRAS RBGS and covers a range of merger stages, morphologies and spectral types. The majority (>60%) of GOALS LIRGs have high 6.2um PAH equivalent widths (EQW > 0.4um) and low levels of silicate absorption (s_9.7um >-1.0). There is a general trend among the U/LIRGs for silicate depth and MIR slope to increase with LIR. U/LIRGs in the late stages of a merger also have on average steeper MIR slopes and higher levels of dust obscuration. Together these trends suggest that as gas & dust is funneled towards the center of a coalescing merger, the nuclei become more compact and obscured. The sources that depart from these correlations have very low PAH EQW (EQW < 0.1um) consistent with their MIR emission being dominated by an AGN. The most heavily dust obscured sources are the most compact in their MIR emission, suggesting that the obscuring (cool) dust is associated with the outer regions of the starburst. As the merger progresses a marked decline is seen for the fraction of high EQW (star formation dominated) sources while the fraction of composite sources increases but the fraction of AGN-dominated sources remains low. When compared to the MIR spectra of submillimeter galaxies (SMGs) at z~2, the average GOALS LIRG is more absorbed at 9.7um and has more PAH emission. However, when the AGN contributions to both the local LIRGs and the high-z SMGs are removed, the average local starbursting LIRG closely resembles the starbursting SMGs.

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