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arXiv 0901.0415astro-ph.GAastro-ph.CO
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后发座星系团内尘埃发射的制约因素

Constraints on the Intracluster Dust Emission in the Coma Cluster of Galaxies

T. Kitayama, Y. Ito, Y. Okada, H. Kaneda, H. Takahashi, N. Ota, T. Onaka, Y. Y. Tajiri, H. Nagata, K. Yamada

摘要:

我们利用斯皮策多波段成像光度计对后发座星系团内尘埃的红外辐射进行了研究。我们的观测产生了有史以来最深的星系团的中红外和远红外图像。在这三个波段中的每一个波段中,我们都没有探测到中心多余分量的特征,这与红外空间天文台(ISO)先前的探测报告相反。我们仍然发现70和160微米之间的亮度比显示出中心过量的边缘符号,与ISO结果定性一致。我们的分析表明,过量的比例更可能是由于微弱的红外源躺在起伏的卷云前景。我们的观测结果表明,在24、70和160微米处,在距离星系团中心100 kpc的范围内,过量辐射的2 σ上限分别为5 x 10^-3 MJy/sr、6 x 10^-2 MJy/sr和7 x 10^-2 MJy/sr。这些值与其他星系团中发现的值一致,表明与星际介质相比,星团中心附近的尘埃不足3个数量级以上。

英文摘要:

We have undertaken a search for the infrared emission from the intracluster dust in the Coma cluster of galaxies by the Multiband Imaging Photometer for Spitzer. Our observations yield the deepest mid and far-infrared images of a galaxy cluster ever achieved. In each of the three bands, we have not detected a signature of the central excess component in contrast to the previous report on the detection by Infrared Space Observatory (ISO). We still find that the brightness ratio between 70 and 160 microns shows a marginal sign of the central excess, in qualitative agreement with the ISO result. Our analysis suggests that the excess ratio is more likely due to faint infrared sources lying on fluctuating cirrus foreground. Our observations yield the 2 sigma upper limits on the excess emission within 100 kpc of the cluster center as 5 x 10^-3 MJy/sr, 6 x 10^-2 MJy/sr, and 7 x 10^-2 MJy/sr, at 24, 70, and 160 microns, respectively. These values are in agreement with those found in other galaxy clusters and suggest that dust is deficient near the cluster center by more than 3 orders of magnitude compared to the interstellar medium.

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