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arXiv · 2610.20260

Constrain the Size of Broad Line Region in NGC 1068 Using Sub-millimeter Excess

Qi Guo·Junzhi Wang·Lingrui Lin·Yuqiang Li·Zhi-yu Zhang·Fengyao Zhu
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Abstract

Constraining the size of broad-line region (BLR) close to the accretion disk in active galactic nuclei (AGNs) is key to understand the central engine and evolution of AGN. We propose a new method to constrain the BLR size, based on millimeter to sub-millimeter spectral energy distribution (SED), from which a sub-millimeter excess may be found. Such excess can be used to determine the solid angle of the free-free emission region from BLR, as a region with high electron density and optically thick at sub-millimeter wavelength for free-free continuum. Millimeter to sub-millimeter SED analysis toward the central source S1 in a nearby type II AGN NGC 1068 was done, which gave an upper limit on the solid angle of BLR region as(4.94 +/- 0.61) *10^-6 arcsec^2, corresponding to a radius no more than 0.085 pc. Such a constraint on the BLR size is important for estimating the masses of central supermassive black holes in AGNs.

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Qi Guo, Junzhi Wang, Lingrui Lin, Yuqiang Li, Zhi-yu Zhang, Fengyao Zhu. 2026-10-14. Constrain the Size of Broad Line Region in NGC 1068 Using Sub-millimeter Excess. https://arxiv.org/abs/2610.20260

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