期刊
ASTROPHYSICAL JOURNAL LETTERS
卷 724, 期 1, 页码 L59-L63出版社
IOP PUBLISHING LTD
DOI: 10.1088/2041-8205/724/1/L59
关键词
galaxies: evolution; quasars: general
资金
- NASA [GO7-8136A, NAS8-39073]
- ASI/INAF [I/023/05]
We report a sizable class of type 1 active galactic nuclei (AGNs) with unusually weak near-infrared (1-3 mu m) emission in the XMM-COSMOS type 1 AGN sample. The fraction of these hot-dust-poor AGNs increases with redshift from 6% at lowredshift (z < 2) to 20% at moderate high redshift (2 < z < 3.5). There is no clear trend of the fraction with other parameters: bolometric luminosity, Eddington ratio, black hole mass, and X-ray luminosity. The 3 mu m emission relative to the 1 mu m emission is a factor of 2-4 smaller than the typical Elvis et al. AGN spectral energy distribution (SED), which indicates a torus covering factor of 2%-29%, a factor of 3-40 smaller than required by unified models. The weak hot dust emission seems to expose an extension of the accretion disk continuum in some of the source SEDs. We estimate the outer edge of their accretion disks to lie at (0.3-2.0) x 10(4) Schwarzschild radii, similar to 10-23 times the gravitational stability radii. Formation scenarios for these sources are discussed.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据