2025/10/06 by Ashutosh Tomar, Tomar, Ashutosh, Suvendu Rakshit +5
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Astrophysics of Galaxies (astro-ph.GA) #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #High Energy Astrophysical Phenomena (astro-ph.HE)
paper · pdf · doi:10.48550/arxiv.2510.04517
openalex publication_date 2025/10/06 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/03
We present measurements of the dusty torus sizes of 51 active galactic nuclei (AGNs) with a redshift of z< 0.8. Our analysis utilizes about 16 years of optical photometric data of 146 AGNs from various time-domain surveys, including ASAS-SN, CRTS, and ZTF, along with 14 years of infrared data in the W1 (∼ 3.4 μm) and W2 (∼ 4.6 μm) bands obtained from the Wide-Field Infrared Survey Explorer (WISE). The estimated dust torus size ranges from 1000 to 3000 days, using both the cross-correlation analysis and lightcurve modeling through `MICA'. The measured lag has been corrected by (1+z)-0.37, to account for cosmological time dilation and the torus temperature-gradient scaling. We conduct a linear regression analysis for both the W1 and W2 bands to examine the radius--luminosity (R--LBOL) relationship under two conditions: one where the slope is fixed at 0.5 and one where it is allowed to vary. For the fixed slope of 0.5, we find the ratio of RBLR: RW1: RW2 to be 1: 9: 12, indicating that the torus lies outside the BLR and that its size increases with wavelength. Furthermore, we determine the relationship between torus size and LBOL, yielding best-fit slopes of 0.413±0.047 for the W1 band and 0.397±0.058 for the W2 band. Both slopes are shallower than predicted by the dust radiation equilibrium model. Furthermore, our findings indicate that the torus size systematically decreases as the Eddington ratio increases, a trend that can be explained by the self-shadowing effects of slim disks.