Scaling Relations of the Dusty Torus with Luminosity and the Broad-Line Region

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Main Authors: Ayubinia, Ashraf, Woo, Jong-Hak, Wang, Shu, Mandal, Amit Kumar, Son, Donghoon
Format: Preprint
Published: 2025
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author Ayubinia, Ashraf
Woo, Jong-Hak
Wang, Shu
Mandal, Amit Kumar
Son, Donghoon
author_facet Ayubinia, Ashraf
Woo, Jong-Hak
Wang, Shu
Mandal, Amit Kumar
Son, Donghoon
contents We measure and compare the size of the dusty torus with active galactic nucleus (AGN) luminosity and the size of the broad-line region (BLR), using a sample of 182 AGNs with the best H$β$ lag measurements. After correcting for accretion-disk contamination, torus sizes are determined from the time lags of the Wide-field Infrared Survey Explorer W1 and W2 band light curves relative to the optical band variability based on the interpolated cross-correlation function (ICCF) analysis and the Multiple and Inhomogeneous Component Analysis. We find that the torus size from the W1-band (W2-band) tightly correlates with the 5100~Å continuum luminosity with an intrinsic scatter of 0.15-0.16 dex and the best-fit slope of $0.35 \pm 0.03$ ($0.33 \pm 0.03$), which is clearly shallower than the expected 0.5 slope from the sublimation radius-luminosity relation. We find a moderate negative trend that higher Eddington AGNs tend to have smaller torus sizes than expected from the best-fit, suggesting the Eddington ratio plays a role in flattening the torus size-luminosity relation. By comparing the torus size with the H$β$ reverberation time lag for a subsample of 67 AGNs, we find that the torus size is a factor of $\sim 10$ and $\sim 14$ larger than the BLR size, respectively for W1 and W2 bands. The torus size based on the W1 (W2) band correlates with the BLR size with the best-fit slope of $1.28 \pm 0.16$ ($1.10 \pm 0.15$), which is comparable but slightly steeper than a linear correlation.
format Preprint
id arxiv_https___arxiv_org_abs_2509_07878
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Scaling Relations of the Dusty Torus with Luminosity and the Broad-Line Region
Ayubinia, Ashraf
Woo, Jong-Hak
Wang, Shu
Mandal, Amit Kumar
Son, Donghoon
Astrophysics of Galaxies
We measure and compare the size of the dusty torus with active galactic nucleus (AGN) luminosity and the size of the broad-line region (BLR), using a sample of 182 AGNs with the best H$β$ lag measurements. After correcting for accretion-disk contamination, torus sizes are determined from the time lags of the Wide-field Infrared Survey Explorer W1 and W2 band light curves relative to the optical band variability based on the interpolated cross-correlation function (ICCF) analysis and the Multiple and Inhomogeneous Component Analysis. We find that the torus size from the W1-band (W2-band) tightly correlates with the 5100~Å continuum luminosity with an intrinsic scatter of 0.15-0.16 dex and the best-fit slope of $0.35 \pm 0.03$ ($0.33 \pm 0.03$), which is clearly shallower than the expected 0.5 slope from the sublimation radius-luminosity relation. We find a moderate negative trend that higher Eddington AGNs tend to have smaller torus sizes than expected from the best-fit, suggesting the Eddington ratio plays a role in flattening the torus size-luminosity relation. By comparing the torus size with the H$β$ reverberation time lag for a subsample of 67 AGNs, we find that the torus size is a factor of $\sim 10$ and $\sim 14$ larger than the BLR size, respectively for W1 and W2 bands. The torus size based on the W1 (W2) band correlates with the BLR size with the best-fit slope of $1.28 \pm 0.16$ ($1.10 \pm 0.15$), which is comparable but slightly steeper than a linear correlation.
title Scaling Relations of the Dusty Torus with Luminosity and the Broad-Line Region
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2509.07878