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arXiv 1206.4063astro-ph.COastro-ph.HE
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z~2处的重遮蔽类星体主星系团是双星系团,而不是大合并

Heavily Obscured Quasar Host Galaxies at z~2 are Disks, Not Major Mergers

Kevin Schawinski, Brooke D. Simmons, Megan Urry, Ezequiel Treister, Eilat Glikman

摘要:

利用哈勃空间望远镜WFC 3/IR深空成像技术对28个尘埃暗星系(DOG)进行了观测,研究了z~2处严重遮蔽类星体宿主星系的性质,探讨了主要合并在驱动黑洞生长中的作用.为这项研究选择的类星体的高水平遮蔽充当了天然的日冕,阻挡了类星体的光,并允许清晰地看到下面的宿主星系。严重遮蔽的类星体样本代表了超大质量黑洞上宇宙质量吸积的一个重要部分,因为类星体已经推断出类星体光度函数破裂周围的热光度。我们发现,只有一小部分(4%,最多11-25%)的类星体宿主星系是主要的合并。与其表面亮度轮廓的拟合表明,90%的宿主星系要么是盘主导的,要么有一个重要的盘。这种盘状的宿主形态,以及相应的凸起弱点,是反对大合并的证据,并表明长期过程是大规模黑洞增长的主要驱动力。最后,我们认为,合并和活动星系核活动的重合是光度依赖的,只有最明亮的类星体被触发的主要合并。

英文摘要:

We explore the nature of heavily obscured quasar host galaxies at z~2 using deep Hubble Space Telescope WFC3/IR imaging of 28 Dust Obscured Galaxies (DOGs) to investigate the role of major mergers in driving black hole growth. The high levels of obscuration of the quasars selected for this study act as a natural coronagraph, blocking the quasar light and allowing a clear view of the underlying host galaxy. The sample of heavily obscured quasars represents a significant fraction of the cosmic mass accretion on supermassive black holes as the quasars have inferred bolometric luminosities around the break of the quasar luminosity function. We find that only a small fraction (4%, at most 11-25%) of the quasar host galaxies are major mergers. Fits to their surface brightness profiles indicate that 90% of the host galaxies are either disk dominated, or have a significant disk. This disk-like host morphology, and the corresponding weakness of bulges, is evidence against major mergers and suggests that secular processes are the predominant driver of massive black hole growth. Finally, we suggest that the co-incidence of mergers and AGN activity is luminosity dependent, with only the most luminous quasars being triggered mostly by major mergers.

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