揭示尘埃：希克森致密群星系核的中红外活动
The Revealing Dust: Mid-Infrared Activity in Hickson Compact Group Galaxy Nuclei
摘要：
我们提供了一个来自12个邻近（z<4500 km/s）Hickson紧致群（HCGs）的46个星系核的样品，并使用了一套完整的1-24 μ m 2 MASS +Spitzer核测光。对于样本中的所有物体，来自恒星光球的蓝色发射在通过3.6微米IRAC波段的近红外中占主导地位。46个星系核中的25个（54%）显示出红色的中红外连续光谱，这是由正在进行的恒星形成和/或吸积到中央黑洞上的热尘埃提供动力的特征。我们介绍了alpha_{IRAC}，一个幂律拟合的4.5-8.0微米IRAC数据的光谱指数，并证明它干净地分离中红外活性和非活性HCG核。这个参数对于识别低到中等亮度的中红外活动比其他测量方法更有效，其他测量方法包括可能由恒星光球发射主导的静止帧λ <3.6微米的数据。虽然HCG星系在这个参数空间中明显具有双峰分布，但斯皮策邻近星系巡天（SINGS）在J波段总星系光度中匹配的比较样本是连续分布的。第二个诊断，24微米发射的分数超过预期的从静止星系，f_{24D}，揭示了额外的3个核是活跃的24微米。比较这两个中红外诊断的核活动，从文献中的光学光谱鉴定揭示了一些差异，我们讨论了区分这些和其他低光度系统的电离辐射源的挑战。我们发现一个显着的中红外活跃星系的分数和总HI质量在一个组之间的相关性，并调查可能的解释，这些结果在一个紧凑的组环境的高度互动的系统中的星系演化。
英文摘要：
We present a sample of 46 galaxy nuclei from 12 nearby (z<4500 km/s) Hickson Compact Groups (HCGs) with a complete suite of 1-24 micron 2MASS+Spitzer nuclear photometry. For all objects in the sample, blue emission from stellar photospheres dominates in the near-IR through the 3.6 micron IRAC band. Twenty-five of 46 (54%) galaxy nuclei show red, mid-IR continua characteristic of hot dust powered by ongoing star formation and/or accretion onto a central black hole. We introduce alpha_{IRAC}, the spectral index of a power-law fit to the 4.5-8.0 micron IRAC data, and demonstrate that it cleanly separates the mid-IR active and non-active HCG nuclei. This parameter is more powerful for identifying low to moderate-luminosity mid-IR activity than other measures which include data at rest-frame lambda<3.6 micron that may be dominated by stellar photospheric emission. While the HCG galaxies clearly have a bimodal distribution in this parameter space, a comparison sample from the Spitzer Nearby Galaxy Survey (SINGS) matched in J-band total galaxy luminosity is continuously distributed. A second diagnostic, the fraction of 24 micron emission in excess of that expected from quiescent galaxies, f_{24D}, reveals an additional 3 nuclei to be active at 24 micron. Comparing these two mid-IR diagnostics of nuclear activity to optical spectroscopic identifications from the literature reveals some discrepancies, and we discuss the challenges of distinguishing the source of ionizing radiation in these and other lower luminosity systems. We find a significant correlation between the fraction of mid-IR active galaxies and the total HI mass in a group, and investigate possible interpretations of these results in light of galaxy evolution in the highly interactive system of a compact group environment.
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。
