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Title: VARIATION OF INNER RADIUS OF DUST TORUS IN NGC4151

Abstract

Long-term optical and near-infrared monitoring observations for a type 1 active galactic nucleus (AGN) NGC 4151 were carried out for six years from 2001 to 2006 by using the MAGNUM telescope, and delayed response of flux variations in the K(2.2 {mu}m) band to those in the V(0.55 {mu}m) band was clearly detected. Based on cross-correlation analysis, we precisely measured a lag time {delta}t for eight separate periods and we found that {delta}t is not constant, changing between 30 and 70 d during the monitoring period. Since {delta}t is the light travel time from the central energy source out to the surrounding dust torus, this is the first convincing evidence that the inner radius of the dust torus did change in an individual AGN. In order to relate such a change of {delta}t with a change of AGN luminosity L, we present a method of taking an average of the observed V-band fluxes that corresponds to the measured value of {delta}t, and we find that the time-changing track of NGC 4151 in the {delta}t versus L diagram during the monitoring period deviates from the relation {delta}t {proportional_to} L {sup 0.5} expected from dust reverberation. This result, combined with the elapsed timemore » from period to period for which {delta}t was measured, indicates that the timescale of dust formation is about one year, which should be taken into account as a new constraint in future studies of dust evolution in AGNs.« less

Authors:
; ;  [1]; ; ;  [2]; ;  [3];  [4];  [5]
  1. Department of Astronomy, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0013 (Japan)
  2. Institute of Astronomy, School of Science, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)
  3. National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
  4. Institute of Space and Astronomical Science, Japan Aerospace Exploration Agency, 3-1-1, Yoshinodai, Sagamihara, Kanagawa 229-8510 (Japan)
  5. Kiso Observatory, Institute of Astronomy, School of Science, University of Tokyo, 10762-30 Mitake, Kiso, Nagano 397-0101 (Japan)
Publication Date:
OSTI Identifier:
21313804
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal (Online)
Additional Journal Information:
Journal Volume: 700; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/700/2/L109; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1538-4357
Country of Publication:
United States
Language:
English
Subject:
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; DUSTS; ENERGY SOURCES; GALACTIC EVOLUTION; GALAXIES; LUMINOSITY; TELESCOPES

Citation Formats

Koshida, Shintaro, Sakata, Yu, Sugawara, Shota, Yoshii, Yuzuru, Minezaki, Takeo, Tomita, Hiroyuki, Kobayashi, Yukiyasu, Suganuma, Masahiro, Enya, Keigo, Aoki, Tsutomu, and Peterson, Bruce A. VARIATION OF INNER RADIUS OF DUST TORUS IN NGC4151. United States: N. p., 2009. Web. doi:10.1088/0004-637X/700/2/L109; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
Koshida, Shintaro, Sakata, Yu, Sugawara, Shota, Yoshii, Yuzuru, Minezaki, Takeo, Tomita, Hiroyuki, Kobayashi, Yukiyasu, Suganuma, Masahiro, Enya, Keigo, Aoki, Tsutomu, & Peterson, Bruce A. VARIATION OF INNER RADIUS OF DUST TORUS IN NGC4151. United States. https://doi.org/10.1088/0004-637X/700/2/L109; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)
Koshida, Shintaro, Sakata, Yu, Sugawara, Shota, Yoshii, Yuzuru, Minezaki, Takeo, Tomita, Hiroyuki, Kobayashi, Yukiyasu, Suganuma, Masahiro, Enya, Keigo, Aoki, Tsutomu, and Peterson, Bruce A. 2009. "VARIATION OF INNER RADIUS OF DUST TORUS IN NGC4151". United States. https://doi.org/10.1088/0004-637X/700/2/L109; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
@article{osti_21313804,
title = {VARIATION OF INNER RADIUS OF DUST TORUS IN NGC4151},
author = {Koshida, Shintaro and Sakata, Yu and Sugawara, Shota and Yoshii, Yuzuru and Minezaki, Takeo and Tomita, Hiroyuki and Kobayashi, Yukiyasu and Suganuma, Masahiro and Enya, Keigo and Aoki, Tsutomu and Peterson, Bruce A.},
abstractNote = {Long-term optical and near-infrared monitoring observations for a type 1 active galactic nucleus (AGN) NGC 4151 were carried out for six years from 2001 to 2006 by using the MAGNUM telescope, and delayed response of flux variations in the K(2.2 {mu}m) band to those in the V(0.55 {mu}m) band was clearly detected. Based on cross-correlation analysis, we precisely measured a lag time {delta}t for eight separate periods and we found that {delta}t is not constant, changing between 30 and 70 d during the monitoring period. Since {delta}t is the light travel time from the central energy source out to the surrounding dust torus, this is the first convincing evidence that the inner radius of the dust torus did change in an individual AGN. In order to relate such a change of {delta}t with a change of AGN luminosity L, we present a method of taking an average of the observed V-band fluxes that corresponds to the measured value of {delta}t, and we find that the time-changing track of NGC 4151 in the {delta}t versus L diagram during the monitoring period deviates from the relation {delta}t {proportional_to} L {sup 0.5} expected from dust reverberation. This result, combined with the elapsed time from period to period for which {delta}t was measured, indicates that the timescale of dust formation is about one year, which should be taken into account as a new constraint in future studies of dust evolution in AGNs.},
doi = {10.1088/0004-637X/700/2/L109; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)},
url = {https://www.osti.gov/biblio/21313804}, journal = {Astrophysical Journal (Online)},
issn = {1538-4357},
number = 2,
volume = 700,
place = {United States},
year = {Sat Aug 01 00:00:00 EDT 2009},
month = {Sat Aug 01 00:00:00 EDT 2009}
}