The first spectroscopic dust reverberation programme on active galactic nuclei: the torus in NGC 5548

Autor: Bradley M. Peterson, R. J. Wilman, Johannes Esser, Hartmut Winkler, Gary J. Ferland, Thaisa Storchi-Bergmann, Andy Lawrence, Michael Fausnaugh, Deepak Malhotra, Aaron J. Barth, D. A. Starkey, Chris Packham, Jörg-Uwe Pott, Daniel Kynoch, Martin Ward, Keith Horne, Hermine Landt, Rogemar A. Riffel, Carolin Villforth
Přispěvatelé: Science & Technology Facilities Council, University of St Andrews. School of Physics and Astronomy, University of St Andrews. St Andrews Centre for Exoplanet Science
Rok vydání: 2019
Předmět:
Seyfert [Galaxies]
Active galactic nucleus
Astrophysics::High Energy Astrophysical Phenomena
astro-ph.GA
FOS: Physical sciences
Astrophysics
Astrophysics::Cosmology and Extragalactic Astrophysics
01 natural sciences
Photometry (optics)
Astronomia infravermelha
emission lines [Quasars]
galaxies [Infrared]
0103 physical sciences
Emissivity
QB Astronomy
Astrophysics::Solar and Stellar Astrophysics
Black-body radiation
010303 astronomy & astrophysics
Quasars
QC
Astrophysics::Galaxy Astrophysics
QB
Physics
Luminous infrared galaxy
Galáxia NGC 5548
010308 nuclear & particles physics
Astronomy and Astrophysics
Torus
Quasar
DAS
Radius
Astrophysics - Astrophysics of Galaxies
Galaxias seyfert
QC Physics
13. Climate action
Space and Planetary Science
Astrophysics of Galaxies (astro-ph.GA)
Astrophysics::Earth and Planetary Astrophysics
individual: NGC 5548 [Quasars]
Zdroj: Monthly Notices of the Royal Astronomical Society
Monthly notices of the Royal Astronomical Society, 2019, Vol.489(2), pp.1572-1589 [Peer Reviewed Journal]
Landt, H, Ward, M J, Kynoch, D, Packham, C, Ferland, G J, Lawrence, A, Pott, J-U, Esser, J, Horne, K, Starkey, D A, Malhotra, D, Fausnaugh, M M, Peterson, B M, Wilman, R J, Riffel, R A, Storchi-Bergmann, T, Barth, A J, Villforth, C & Winkler, H 2019, ' The first spectroscopic dust reverberation programme on active galactic nuclei : the torus in NGC 5548 ', Monthly Notices of the Royal Astronomical Society, vol. 489, no. 2, pp. 1572-1589 . https://doi.org/10.1093/mnras/stz2212
Repositório Institucional da UFRGS
Universidade Federal do Rio Grande do Sul (UFRGS)
instacron:UFRGS
DOI: 10.1093/mnras/stz2212
Popis: We have recently initiated the first spectroscopic dust reverberation programme on active galactic nuclei (AGN) in the near-infrared. Spectroscopy enables measurement of dust properties, such as flux, temperature and covering factor, with higher precision than photometry. In particular, it enables measurement of both luminosity-based dust radii and dust response times. Here we report results from a one-year campaign on NGC 5548. The hot dust responds to changes in the irradiating flux with a lag time of ~70 light-days, similar to what was previously found in photometric reverberation campaigns. The mean and rms spectra are similar, implying that the same dust component dominates both the emission and the variations. The dust lag time is consistent with the luminosity-based dust radius only if we assume a wavelength-independent dust emissivity-law, i.e. a blackbody, which is appropriate for grains of large sizes (of a few microns). For such grains the dust temperature is ~1450 K. Therefore, silicate grains have most likely evaporated and carbon is the main chemical component. But the hot dust is not close to its sublimation temperature, contrary to popular belief. This is further supported by our observation of temperature variations largely consistent with a heating/cooling process. Therefore, the inner dust-free region is enlarged and the dusty torus rather a "dusty wall", whose inner radius is expected to be luminosity-invariant. The dust-destruction mechanism that enlarges the dust-free region seems to partly affect also the dusty region. We observe a cyclical decrease in dust mass with implied dust reformation times of ~5-6 months.
22 pages, 13 figures, accepted for publication in MNRAS
Databáze: OpenAIRE
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