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arXiv 1406.3891astro-ph.GA
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发光红外星系II的中红外特性:探测GOALS样品的尘埃和气体物理

Mid-Infrared Properties of Luminous Infrared Galaxies II: Probing the Dust and Gas Physics of the GOALS Sample

Sabrina Stierwalt, Lee Armus, Vassilis Charmandaris, Tanio Diaz-Santos, Jason Marshall, Aaron Evans, Sebastian Haan, Justin Howell, Kazushi Iwasawa, Dongchan Ki… 展开作者

Sabrina Stierwalt, Lee Armus, Vassilis Charmandaris, Tanio Diaz-Santos, Jason Marshall, Aaron Evans, Sebastian Haan, Justin Howell, Kazushi Iwasawa, Dongchan Kim, Eric J. Murphy, Jeff A. Rich, Henrik W. W. Spoon, Hanae Inami, Andreea Petric, Vivian U

摘要:

大天文台全天LIRG巡天(GOALS)是对局部宇宙中的亮红外星系(LIRGs)进行的全面,多波长研究。本文给出了244个LIRG核5- 38 μ m低分辨中红外Spitzer IRS谱的多组分谱分解分析结果。详细的拟合和高质量的光谱允许表征的个人PAH功能,温暖的分子氢发射,和光学深度的硅酸盐尘埃颗粒和水冰。我们发现,星暴LIRGs,这构成了大多数的GOALS,是非常一致的,在它们的MIR特性(即tau_9.7um,τ_ice,氖线和PAH特征比)。然而,由于它们的PAH EQW减少,通常是一个越来越占主导地位的活动星系核的指标,LIRG涵盖了这些MIR参数的更大范围。多环芳烃对LIRGs中总L(IR)的贡献在2-29%之间变化,LIRGs在第一次遇到前平均显示出较高的L(PAH)/L(IR)比值。我们观察到的强度之间的相关性的星暴(IR 8)和PAH馏分在8微米,但不是与7.7至11.3 PAH的比例,这表明分数PDR的排放,而不是整体的粮食性质,是与上升IR 8的星系的星暴主序星。我们在6%的样品中检测到结晶硅酸盐特征,但仅在最模糊的源中(s_9.7um < -1.24)。在11%(56%)的目标激光陀螺(ULIRG)中观察到冰吸收特征。大多数GOALS LIRGs的L(H2)/L(PAH)比高于正常恒星形成星系的L(H2)/L(PAH)比,并且随着L(H2)的增加,L(H2)/L(PAH)比呈现增加的趋势。虽然恒星的形成似乎是主要的过程,负责激发H2在大多数的GOALS星系,一个子集的LIRG(10%)显示过量的H2排放与PDR模型不一致,可能是由冲击或活动星系核引起的外流。

英文摘要:

The Great Observatories All-Sky LIRG Survey (GOALS) is a comprehensive, multiwavelength study of luminous infrared galaxies (LIRGs) in the local universe. Here we present the results of a multi-component, spectral decomposition analysis of the low resolution mid-IR Spitzer IRS spectra from 5-38um of 244 LIRG nuclei. The detailed fits and high quality spectra allow for characterization of the individual PAH features, warm molecular hydrogen emission, and optical depths for silicate dust grains and water ices. We find that starbursting LIRGs, which make up the majority of GOALS, are very consistent in their MIR properties (i.e. tau_9.7um, tau_ice, neon line and PAH feature ratios). However, as their PAH EQW decreases, usually an indicator of an increasingly dominant AGN, LIRGs cover a larger spread in these MIR parameters. The contribution from PAHs to the total L(IR) in LIRGs varies from 2-29% and LIRGs prior to their first encounter show higher L(PAH)/L(IR) ratios on average. We observe a correlation between the strength of the starburst (IR8) and the PAH fraction at 8um but not with the 7.7 to 11.3 PAH ratio, suggesting the fractional PDR emission, and not the overall grain properties, is associated with the rise in IR8 for galaxies off the starburst main sequence. We detect crystalline silicate features in 6% of the sample but only in the most obscured sources (s_9.7um < -1.24). Ice absorption features are observed in 11% (56%) of GOALS LIRGs (ULIRGs). Most GOALS LIRGs have L(H2)/L(PAH) ratios elevated above those observed for normal star-forming galaxies and exhibit a trend for increasing L(H2)/L(PAH) ratio with increasing L(H2). While star formation appears to be the dominant process responsible for exciting the H2 in most of the GOALS galaxies, a subset of LIRGs (10%) show excess H2 emission that is inconsistent with PDR models and may be excited by shocks or AGN-induced outflows.

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