INSPIRALLING SUPERMASSIVE BLACK HOLES: A NEW SIGNPOST FOR GALAXY MERGERS
INSPIRALLING SUPERMASSIVE BLACK HOLES: A NEW SIGNPOST FOR GALAXY MERGERS
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DOI：
10.1088/0004-637x/698/1/956
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发表时间：
2008-10
期刊：
影响因子：
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通讯作者：
J. Comerford;B. Gerke;J. Newman;M. Davis;R. Yan;M. Cooper;S. Faber;D. Koo;A. Coil;A. Coil-A
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文献类型：
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作者：
J. Comerford;B. Gerke;J. Newman;M. Davis;R. Yan;M. Cooper;S. Faber;D. Koo;A. Coil;A. Coil-A
我们提出了一种新的技术，观测识别星系合并光谱，而不是通过主机星系成像。我们的技术利用超大质量黑洞（SMBHs）的动力学的活动星系核（AGN）的合并残余星系。因为宇宙的结构是通过星系合并建立起来的，几乎所有的星系都有一个中央SMBH，一些星系应该在它们的中心附近拥有两个SMBH，作为最近合并的结果。这些SMBH螺旋形地到达合并后的残余星系的中心，其中一个或两个SMBH可能为活动星系核提供能量。利用DEEP 2星系红移巡天，我们观测了1881个红星系，其中91个具有[O iii]和Hβ发射线，表明Seyfert 2活动。其中，32个活动星系核的[O iii]发射线红移与宿主星系的恒星红移明显不同，对应的速度偏移为1050 km s-1至10300 km s-1。其中两个活动星系核呈现双峰[O iii]发射线，而其余30个活动星系核每个都呈现一组速度偏移[O iii]发射线。在探索了这些速度偏移的各种物理模型后，我们认为最有可能的解释是合并残余星系中的螺旋SMBHs。基于这种解释，我们发现大约一半的红色星系的活动星系核也合并残留物，这意味着合并可能会触发活动星系核活动的红色星系。我们发现的活动星系核速度偏移意味着在红移为0.34 < z < 0.82的红星系中，合并分数为1.30%，合并率为1.33合并Gyr−1。
We present a new technique for observationally identifying galaxy mergers spectroscopically rather than through host galaxy imaging. Our technique exploits the dynamics of supermassive black holes (SMBHs) powering active galactic nuclei (AGNs) in merger-remnant galaxies. Because structure in the universe is built up through galaxy mergers and nearly all galaxies host a central SMBH, some galaxies should possess two SMBHs near their centers as the result of a recent merger. These SMBHs spiral to the center of the resultant merger-remnant galaxy, and one or both of the SMBHs may power AGNs. Using the DEEP2 Galaxy Redshift Survey, we have examined 1881 red galaxies, of which 91 exhibit [O iii] and Hβ emission lines indicative of Seyfert 2 activity. Of these, 32 AGNs have [O iii] emission-line redshifts significantly different from the redshifts of the host galaxies' stars, corresponding to velocity offsets of ∼50 km s−1 to ∼300 km s−1. Two of these AGNs exhibit double-peaked [O iii] emission lines, while the remaining 30 AGNs each exhibit a single set of velocity-offset [O iii] emission lines. After exploring a variety of physical models for these velocity offsets, we argue that the most likely explanation is inspiralling SMBHs in merger-remnant galaxies. Based on this interpretation, we find that roughly half of the red galaxies hosting AGNs are also merger remnants, which implies that mergers may trigger AGN activity in red galaxies. The AGN velocity offsets we find imply a merger fraction of ∼30% and a merger rate of ∼3 mergers Gyr−1 for red galaxies at redshifts 0.34 < z < 0.82.