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arXiv 0803.2229astro-ph
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在发光红外线星系中理解亚角秒尺度上8微米与Pa-α的关系

Understanding the 8 micron vs. Pa-alpha relationship on sub-arcsecond scales in Luminous Infrared Galaxies

Tanio Diaz-Santos, Almudena Alonso-Herrero, Luis Colina, Christopher Packham, James T. Radomski, Charles M. Telesco

摘要:

这项工作详细探讨了在10个低z LIRG样品中确定的122个HII区域的8微米和Pa-α发射之间的关系,这些低z LIRG具有几乎恒定的金属丰度(12 + log(O/H)~ 8.8)。我们使用Gemini/T-ReCS高空间分辨率(<~ 0.4”~ 120 pc,我们的样品的平均距离为60 Mpc)中红外成像(8.7微米或10.3微米)以及HST/NICMOS连续谱和Pa-α图像。LIRG HII区将高金属丰度SINGS星系中HII结的L_8微米与L_Pa-α关系扩展了约两个数量级。由于LIRG样品的金属丰度几乎是恒定的,我们可以排除这种影响作为关系中看到的散射的原因。反过来,它归因于两个效应:年龄和PAH特征。在LIRG HII区,L_8 μ m/L_Pa-α比值的变化为10倍,这一比值由瞬时恒星形成和年龄为400万~ 750万年的模型再现。对于给定的年龄,模型预测周围的剩余分散可能是由于PAH特征(在我们的情况下为8.6微米)对星系之间8微米发射的不同贡献。

英文摘要:

This work explores in detail the relation between the 8 micron and the Pa-alpha emissions for 122 HII regions identified in a sample of 10 low-z LIRGs with nearly constant metallicity (12 + log (O/H) ~ 8.8). We use Gemini/T-ReCS high-spatial resolution (<~ 0.4" ~ 120 pc for the average distance of 60 Mpc of our sample) mid-infrared imaging (at 8.7 micron or 10.3 micron) together with HST/NICMOS continuum and Pa-alpha images. The LIRG HII regions extend the L_8micron vs. L_Pa-alpha relation found for HII knots in the high-metallicity SINGS galaxies by about two orders of magnitude to higher luminosities. Since the metallicity of the LIRG sample is nearly constant, we can rule out this effect as a cause for the scatter seen in the relationship. In turn, it is attributed to two effects: age and PAH features. The L_8micron/L_Pa-alpha ratio, which varies by a factor of ten for the LIRG HII regions, is reproduced by a model with instantaneous star formation and ages ranging from ~ 4 to 7.5 Myr. The remaining dispersion around the model predictions for a given age is probably due to differential contributions of the PAH features (the 8.6 micron, in our case) to the 8 micron emission from galaxy to galaxy.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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