2003/11/18 by Takeo Minezaki, T. Minezaki, Yuzuru Yoshii +12 · 2 citations
Physics and Astronomy · #Active galactic nucleus #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Galaxy #Geometry #Infrared #Lag #Light curve #Physics #RADIUS #Reverberation mapping #Stellar, planetary, and galactic studies #Sublimation (psychology) #Time lag #Torus #astro-ph
paper · pdf · doi:10.1086/381364
published as Astrophys.J. 600 (2003) L35-L38 · Accepted for publication in ApJ Letters, 13 pages, 3 figures; Corrected typos
arxiv created 2003/11/18 · openalex publication_date 2003/12/12 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The most intense monitoring observations yet made were carried out on the Seyfert 1 galaxy NGC 4151 in the optical and near-infrared wave bands. A lag from the optical light curve to the near-infrared light curve was measured. The lag time between the V and K light curves at the flux minimum in 2001 was precisely 48 days, as determined by a cross-correlation analysis. The correlation between the optical luminosity of an active galactic nucleus (AGN) and the lag time between the UV/optical and the near-infrared light curves is presented for NGC 4151 in combination with previous lag-time measurements of NGC 4151 and other AGNs in the literature. This correlation is interpreted as thermal dust reverberation in an AGN, where the near-infrared emission from an AGN is expected to be the thermal reradiation from hot dust surrounding the central engine at a radius where the temperature equals that of the dust sublimation temperature. We find that the inner radius of the dust torus in NGC 4151 is ~0.04 pc corresponding to the measured lag time, well outside the broad-line region determined by other reverberation studies of the emission lines.