We have newly identified a substantial number of type 1 active galactic
nuclei (AGN) featuring weak broad-line regions (BLRs) at z < 0.2 from detailed
analysis of galaxy spectra in the Sloan Digital Sky Survey Data Release 7.
These objects predominantly show a stellar continuum but also a broad H-alpha
emission line, indicating the presence of a low-luminosity AGN oriented so that
we are viewing the central engine directly without significant obscuration.
These accreting black holes have previously eluded detection due to their weak
nature. The new BLR AGNs we found increased the number of known type 1 AGNs by
49%. Some of these new BLR AGNs were detected at the Chandra X-ray Observatory,
and their X-ray properties confirm that they are indeed type 1 AGN. Based on
our new and more complete catalogue of type 1 AGNs, we derived the type 1
fraction of AGNs as a function of [OIII] 5007 emission luminosity and explored
the possible dilution effect on the obscured AGN due to star-formation. The new
type 1 AGN fraction shows much more complex behavior with respect to black hole
mass and bolometric luminosity than suggested by the existing receding torus
model. The type 1 AGN fraction is sensitive to both of these factors, and there
seems to be a sweet spot (ridge) in the diagram of black hole mass and
bolometric luminosity. Furthermore, we present a hint that the Eddington ratio
plays a role in determining the opening angles.

在斯隆数字天文巡天数据发布 7 中，我们新鉴定了大量 z < 0.2 的特 1 活动星系核（AGN），它们有弱的宽带线区域（BLRs），主要表现出恒星连续体和宽 H-alpha 发射线并由其低辐射力 AGN 控制；通过对这些 AGN 进行更全面的分类，研究发现黑洞质量和辐射通量对特 1 AGN 的作用，Eddington 比例在决定开口角度时也十分重要。