為了要理解黑洞與星系間的共同演化，在宇宙中找尋活躍星系核是非常重要的，因為當今的研究普遍認為，在每個超大質量黑洞中都有一個活躍星系核。然而，光學、紫外光及軟Ｘ射線的天文觀測常常會錯失第二型活躍星系核，因為活躍星系核常被宇宙間的塵埃所包覆，因此這些觀測沒有辦法探查到第二型活躍星系核。紅外線望遠鏡之探測可以幫助我們解決這個問題，因為可以穿透星際塵埃。先前的大型紅外線光譜計畫，諸如WISE及Spitzer太空望遠鏡，在它們的濾鏡間都有無法被觀測到的波長。因此，運用這些望遠鏡來進行恆星生成星系及活躍星系核的分類是受到限制的。AKARI紅赤外太空望遠鏡具有非常獨特的連續九個波長帶的濾鏡，覆蓋範圍由近紅外線至遠紅外線。AKARI的優勢可以提供給我們完整的恆星生成星系及活躍星系核的分類。擁有星系完整的紅外線光譜，輔以新穎的光譜能量分析擬合軟體，CIGALE，我們可以有效的找到紅外線活躍星系核。在本研究中，我們在AKARI/IRC北黃極場中找到了126個第二型活躍星系核，我們也分析這些活躍星系核對於整個星系紅外線亮度的貢獻，我們發現，在定值的紅外線亮度，當星系的紅移值變大時，活躍星系核的貢獻度也會隨之提高。在接下來的大型紅外線調查，例如詹姆斯·韋伯太空望遠鏡，我們期待可以發現更多的第二型活躍星系核，並且對黑洞與星系的共同演化有更全面性的了解。

In order to understand the interaction between the central black hole and the whole galaxy or their co-evolution history along with cosmic time, a complete census of active galactic nuclei (AGN) is crucial. However, AGNs are often missed in optical, UV and soft X-ray observations since they could be obscured by gas and dust. A mid-infrared (mid-IR) survey supported by multiwavelength data is one of the best ways to find obscured AGN activities because it suffers less from extinction. Previous large IR photometric surveys, e.g., WISE and Spitzer, have gaps between the mid-IR filters. Therefore, star forming galaxy (SFG)-AGN diagnostics in the mid-IR were limited. The AKARI satellite has a unique continuous 9-band filter coverage in the near to mid-IR wavelengths. In this work, we take advantage of the state-of-the-art spectral energy distribution (SED) modelling software,CIGALE, to find AGNs in mid-IR. We found 126 AGNs in the NEP-Wide field with this method. We also investigate the energy released from the AGN as a fraction of the total IR luminosity of a galaxy. We found that the AGN contribution is larger at higher redshifts for a given IR luminosity. With the upcoming deep IR surveys, e.g., JWST, we expect to find more AGNs with our method.

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