Variability of Seyfert galaxies in the near-infrared — II. The unusual starburst Seyfert NGC 7469

Glass, Ian S.

doi:10.1046/j.1365-8711.1998.01429.x

Cited by 12 publications

(5 citation statements)

References 13 publications

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“…Oknyanskij & Horne ( 2001) have taken the data of Glass (1998) and cross-correlated it with published and unpublished U photometry (e.g. Doroshenko, Lyutyi & Rakhimov, 1989;Chuvaev, Lyutyi & Doroshenko, 1990), finding that there are delays of 52±15d at K and 60±10d at L. The present data, using only the published U photometry, yield, with lower significance, a delay between U and L of ∼21d and between J and L of ∼40d.…”

Section: Ngc 7469supporting

confidence: 51%

“…Galaxies with nuclei that are clearly perceived to be obscured have redder variable components. The colours of the variable components have also been found to stay constant or very nearly constant in the nearinfrared (Glass, 1992), and a number of examples have already been published: NGC 3783 (Glass 1992), NGC 1068 (Glass 1995), NGC 2992 (Glass 1997a) and NGC 7469 (Glass 1998). Figs 4a-f, 5 and 6 give data in the form of flux-flux plots for many of the galaxies in this paper.…”

Section: Spectral Energy Distributions Of the Variable Componentsmentioning

confidence: 62%

“…As already mentioned, two very interesting cases of large amplitude short-term events are seen in NGC 2992, which seems to have experienced a substantial outburst (Glass, 1997a) and NGC 7469, whose nuclear source virtually shut off for a short period (Glass, 1998).…”

Section: Variability Patternsmentioning

confidence: 77%

“…Another example of this kind is NGC 7469, which was discussed in detail by Glass (1998). A circumnuclear ring exists in this galaxy and appears to constitute a non-variable contribution in addition to the ordinary galaxy stellar component.…”

Section: Other Constant Componentsmentioning

confidence: 97%

“…The infrared output of NGC 1068 was shown to have increased by a factor of two between the early 1970s and 1995 by Glass (1995). The galaxy NGC 2992 showed an energetic flare-like outburst with a decay time of about 900d (Glass, 1997a) and NGC 7469 showed a dramatic but relatively short-lived decline in its nuclear energy output in October 1989 (Glass 1998).…”

Section: Introductionmentioning

confidence: 99%

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Long-term infrared photometry of Seyferts

Glass

2004

Monthly Notices of the Royal Astronomical Society

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103

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Long‐term (up to 10 000 d) monitoring has been undertaken for 41 Seyferts in the near‐infrared (1.25–3.45 μm). All but two showed variability, with amplitudes at K in the range <0.1 to >1.1 mag. The time‐scale for detectable change is from about one week to a few years. Where contemporary observations of variability in X‐rays, ultraviolet (UV) or visible light exist, it is found that the near‐infrared varies in a similar way, though in some cases the shorter‐wavelength infrared (IR) bands are diluted by underlying galaxy radiation. A simple cross‐correlation study indicates that there is evidence for delays of up to several hundred d between the variations seen at the shortest wavelengths (U or J) and the longest (L) in many galaxies. In particular, the data for Fairall 9 now extend to twice the interval covered in earlier publications and the delay between its UV and IR outputs is seen to persist. An analysis of the fluxes shows that, for any given galaxy, the colours of the variable component of its nucleus are usually independent of the level of activity. The state of activity of the galaxy can be parameterized. Taken over the whole sample, the colours of the variable components fall within moderately narrow ranges. In particular, the H−K colour is appropriate to a blackbody of temperature 1600 K. The H−K excess for a heavily reddened nucleus can be determined and used to find EB−V, which can be compared to the values found from the visible region broad line ratios. Using flux–flux diagrams, the flux within the aperture from the underlying galaxies can often be determined without the need for model surface brightness profiles. In many galaxies it is apparent that there must be an additional constant contribution from warm dust.

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Section: Ngc 7469supporting

confidence: 51%

Section: Spectral Energy Distributions Of the Variable Componentsmentioning

confidence: 62%

Section: Variability Patternsmentioning

confidence: 77%

Section: Other Constant Componentsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Long-term infrared photometry of Seyferts

Glass

2004

Monthly Notices of the Royal Astronomical Society

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103

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Disentangling the optical AGN and host-galaxy luminosity with a probabilistic flux variation gradient

Gianniotis

Núñez

Polsterer

2022

A&A

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Context. We present a novel probabilistic flux variation gradient (PFVG) approach to separate the contributions of active galactic nuclei (AGN) and host galaxies in the context of photometric reverberation mapping (PRM) of AGN. Aims. We explored the ability of recovering the fractional contribution in a model-independent way using the entire set of light curves obtained through different filters and photometric apertures simultaneously. Methods. The method is based on the observed “bluer when brighter” phenomenon that is attributed to the superimposition of a two-component structure; the red host galaxy, which is constant in time, and the varying blue AGN. We describe the PFVG mathematical formalism and demonstrate its performance using simulated light curves and available PRM observations. Results. The new probabilistic approach is able to recover host-galaxy fluxes to within 1% precision as long as the light curves do not show a significant contribution from time delays. This represents a significant improvement with respect to previous applications of the traditional FVG method to PRM data. Conclusions. The proposed PFVG provides an efficient and accurate way to separate the AGN and host-galaxy luminosities in PRM monitoring data. The method will be especially helpful in the case of large upcoming photometric survey telescopes such as the public optical/near-infrared Legacy Survey of Space and Time (LSST) at the Vera C. Rubin Observatory. Finally, we have made the algorithms freely available as part of our Julia PFVG package.

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A high angular resolution view of the PAH emission in Seyfert galaxies using JWST/MRS data

García-Bernete

Rigopoulou

Alonso‐Herrero

et al. 2022

A&A

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Polycyclic aromatic hydrocarbons (PAHs) are carbon-based molecules that are ubiquitous in a variety of astrophysical objects and environments. In this work we use JWST/MIRI MRS spectroscopy of three Seyferts to compare their nuclear PAH emission with that of star-forming (SF) regions. This study represents the first of its kind to use sub-arcsecond angular resolution data of local luminous Seyferts (Lbol > 1044.46 erg s−1) with a wide wavelength coverage (4.9–28.1 μm). We present an analysis of their nuclear PAH properties by comparing the observed ratios with PAH diagnostic model grids derived from theoretical spectra. Our results show that a suite of PAH features is present in the innermost parts of luminous Seyfert galaxies (∼0.45″ at 12 μm; in the inner ∼142–245 pc). We find that the nuclear regions of active galactic nuclei (AGN) lie at different positions of the PAH diagnostic diagrams, whereas the SF regions are concentrated around the average values of SF galaxies. In particular, we find that the nuclear PAH emission mainly originates in neutral PAHs. In contrast, PAH emission originating in the SF regions favours ionised PAH grains. The observed PAH ratios in the nuclear region of the AGN-dominated galaxy NGC 6552 indicate the presence of larger PAH molecules compared with those of the SF regions. Therefore, our results provide evidence that the AGN have a significant impact on the ionisation state (and probably the size) of the PAH grains on scales of ∼142–245 pc.

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Variability of Seyfert galaxies in the near-infrared — II. The unusual starburst Seyfert NGC 7469

Cited by 12 publications

References 13 publications

Long-term infrared photometry of Seyferts

Long-term infrared photometry of Seyferts

Disentangling the optical AGN and host-galaxy luminosity with a probabilistic flux variation gradient

A high angular resolution view of the PAH emission in Seyfert galaxies using JWST/MRS data

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