Constrain the Size of Broad Line Region in NGC 1068 Using Sub-millimeter Excess
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.
Versions
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BibTeX
@misc{guo2026constrain,
title = {{Constrain the Size of Broad Line Region in NGC 1068 Using Sub-millimeter Excess}},
author = {Qi Guo and Junzhi Wang and Lingrui Lin and Yuqiang Li and Zhi-yu Zhang and Fengyao Zhu},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.20260},
eprint = {2610.20260},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.20260},
}
RIS
TY - UNPB
TI - Constrain the Size of Broad Line Region in NGC 1068 Using Sub-millimeter Excess
AU - Qi Guo
AU - Junzhi Wang
AU - Lingrui Lin
AU - Yuqiang Li
AU - Zhi-yu Zhang
AU - Fengyao Zhu
PY - 2026
DA - 2026/10/16
PB - arXiv
DO - 10.48550/arxiv.2610.20260
UR - https://arxiv.org/abs/2610.20260
AB - 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.
ER -