Spitzer space telescope measurements of dust reverberation lags in the Seyfert 1 galaxy NGC 6418
MetadataShow full item record
We present results from a 15 month campaign of high-cadence (∼3 days) mid-infrared Spitzer and optical (B and V) monitoring of the Seyfert 1 galaxy NGC 6418, with the objective of determining the characteristic size of the dusty torus in this active galactic nucleus (AGN). We find that the 3.6 and 4.5 μm flux variations lag behind those of the optical continuum by days and days, respectively. We report a cross-correlation time lag between the 4.5 and 3.6 μm flux of days. The lags indicate that the dust emitting at 3.6 and 4.5 μm is located at a distance light-month () from the source of the AGN UV-optical continuum. The reverberation radii are consistent with the inferred lower limit to the sublimation radius for pure graphite grains at 1800 K, but smaller by a factor of ∼2 than the corresponding lower limit for silicate grains; this is similar to what has been found for near-infrared (K-band) lags in other AGNs. The 3.6 and 4.5 μm reverberation radii fall above the K-band size-luminosity relationship by factors and , respectively, while the 4.5 μm reverberation radius is only 27% larger than the 3.6 μm radius. This is broadly consistent with clumpy torus models, in which individual optically thick clouds emit strongly over a broad wavelength range.
Vazquez , B , Grant , P , Richmond , M , Robinson , A , Axon , D J , Horne , K , Almeyda , T , Fausnaugh , M , Peterson , B M , Bottorff , M , Gallimore , J , Eltizur , M , Netzer , H , Storchi-Bergmann , T , Marconi , A , Capetti , A , Batcheldor , D , Buchanan , C , Stirpe , G , Kishimoto , M , Packham , C , Perez , E , Tadhunter , C , Upton , J & Estrada-Carpenter , V 2015 , ' Spitzer space telescope measurements of dust reverberation lags in the Seyfert 1 galaxy NGC 6418 ' Astrophysical Journal , vol 801 , no. 2 . DOI: 10.1088/0004-637X/801/2/127
© 2015. The American Astronomical Society. All rights reserved. Reproduced in accordance with AAS copyright policy.
Items in the St Andrews Research Repository are protected by copyright, with all rights reserved, unless otherwise indicated.
Showing items related by title, author, creator and subject.
Mendez Abreu, Jairo; Debattista, V. P.; Corsini, E. M.; Aguerri, J. A. L. (2014-12) - Journal articleContext. Historically, galaxy bulges were thought to be single-component objects at the center of galaxies. However, this picture is now questioned since different bulge types with different formation paths, namely classical ...
The UV continua and inferred stellar populations of galaxies at z ≃ 7-9 revealed by the Hubble Ultra-Deep Field 2012 campaign Dunlop, J. S.; Rogers, A. B.; McLure, R. J.; Ellis, R. S.; Robertson, B. E.; Koekemoer, A.; Dayal, P.; Curtis-Lake, E.; Wild, Vivienne; Charlot, S.; Bowler, R. A. A.; Schenker, M. A.; Ouchi, M.; Ono, Y.; Cirasuolo, M.; Furlanetto, S. R.; Stark, D. P.; Targett, T. A.; Schneider, E. (2013-07-11) - Journal articleWe use the new ultra-deep, near-infrared imaging of the Hubble Ultra-Deep Field (HUDF) provided by our UDF12 Hubble Space Telescope (HST) Wide Field Camera 3/IR campaign to explore the rest-frame ultraviolet (UV) properties ...
Galaxy And Mass Assembly (GAMA) : the wavelength-dependent sizes and profiles of galaxies revealed by MegaMorph Vulcani, Benedetta; Bamford, Steven P.; Haeussler, Boris; Vika, Marina; Rojas, Alex; Agius, Nicola K.; Baldry, Ivan; Bauer, Amanda E.; Brown, Michael J. I.; Driver, Simon; Graham, Alister W.; Kelvin, Lee S.; Liske, Jochen; Loveday, Jon; Popescu, Cristina C.; Robotham, Aaron S. G.; Tuffs, Richard J. (2014-06) - Journal articleWe investigate the relationship between colour and structure within galaxies using a large, volume-limited sample of bright, low-redshift galaxies with optical-near-infrared imaging from the Galaxy And Mass Assembly survey. ...