The luminosity-dependent contribution from the broad-line region to the wavelength-dependent lags in Mrk 110

Vincentelli, Federico; McHardy, I. M.; Santisteban, V. Hernández; Cackett, Edward M.; Gelbord, Jonathan; Horne, K.; Miller, Josephine B.; Lobban, A.

doi:10.1093/mnrasl/slac009

“…The Night 2 data strongly depart from the expected lag-wavelength trend in that the zband lag is shorter than the i-band lag, although the dominant reverberation behavior apparent in the combined Night 1+2 data follows the τ ∝ λ 4/3 model closely. Very few AGN have high-cadence continuum reverberation mapping data spanning timescales long enough to search for temporal changes in lags (one example is Mrk 110, which has shown evidence for a time-varying BLR contribution; Vincentelli et al 2022). In light of this unusual behavior, it would be particularly useful to carry out monitoring of NGC 4395 over a longer time baseline, and over a broader range of wavelengths (ideally including X-ray and UV observations) to better explore temporal changes in lag behavior, and test whether variations in lag are correlated with any other observable properties.…”

Section: Discussionmentioning

confidence: 99%

Optical Continuum Reverberation in the Dwarf Seyfert Nucleus of NGC 4395

Montano¹,

Guo²,

Barth³

et al. 2022

ApJL

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In order to constrain the size of the optical continuum emission region in the dwarf Seyfert 1 galaxy NGC 4395 through reverberation mapping, we carried out high-cadence photometric monitoring in the griz filter bands on two consecutive nights in 2022 April using the four-channel MuSCAT3 camera on the Faulkes Telescope North at Haleakalā Observatory. Correlated variability across the griz bands is clearly detected, and the r-, i-, and z-band light curves show lags of 7.72 − 1.09 + 1.01 , 14.16 − 1.25 + 1.22 , and 20.78 − 2.09 + 1.99 minutes with respect to the g band when measured using the full-duration light curves. When lags are measured for each night separately, the Night 2 data exhibit lower cross-correlation amplitudes and shorter lags than the Night 1 light curves. Using the full-duration lags, we find that the lag–wavelength relationship is consistent with the τ ∝ λ 4/3 dependence found for more luminous active galactic nuclei. Combining our results with continuum lags measured for other objects, the lag between g and z band scales with optical continuum luminosity as τ gz ∝ L 0.56±0.05, similar to the scaling of broad-line region size with luminosity, reinforcing recent evidence that diffuse continuum emission from the broad-line region may contribute substantially to optical continuum variability and reverberation lags.

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“…The Night 2 data strongly depart from the expected lag-wavelength trend in that the z-band lag is shorter than the i-band lag, although the dominant reverberation behavior apparent in the combined Night 1+2 data follows the τ ∝ λ 4/3 model closely. Very few AGN have high-cadence continuum reverberation mapping data spanning timescales long enough to search for temporal changes in lags (one example is Mrk 110 which has shown evidence for a time-varying BLR contribution; Vincentelli et al 2022). In light of this unusual behavior, it would be particularly useful to carry out monitoring of NGC 4395 over a longer time baseline, and over a broader range of wavelengths (ideally including X-ray and UV observations) to better explore temporal changes in lag behavior, and test whether variations in lag are correlated with any other observable properties.…”

Section: Discussionmentioning

confidence: 99%

Optical Continuum Reverberation in the Dwarf Seyfert Nucleus of NGC 4395

Montano,

Guo,

Barth

et al. 2022

Preprint

2

0

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The nearby dwarf spiral galaxy NGC 4395 contains a broad-lined active galactic nucleus (AGN) of exceptionally low luminosity powered by accretion onto a central black hole of very low mass (∼ 10 4 − 10 5 M ). In order to constrain the size of the optical continuum emission region through reverberation mapping, we carried out high-cadence photometric monitoring of NGC 4395 in the griz filter bands on two consecutive nights in 2022 April using the four-channel MuSCAT3 camera on the Faulkes Telescope North at Haleakalā Observatory. Correlated variability across the griz bands is clearly detected, and the r, i, and z band light curves show lags of 8.4 +1.0 −1.1 , 14.2 +1.2 −1.4 , and 20.4 +2.0 −2.1 minutes with respect to the g band when measured using the full-duration light curves. When lags are measured for each night separately, the Night 2 data exhibit lower cross-correlation amplitudes and shorter lags than the Night 1 light curves. Using the full-duration lags, we find that the lagwavelength relationship is consistent with the τ ∝ λ 4/3 dependence found for more luminous AGN. Combining our results with continuum lags measured for other objects, the lag between g and z band scales with optical continuum luminosity as τ gz ∝ L 0.56±0.05 , similar to the scaling of broad-line region size with luminosity, reinforcing recent evidence that diffuse continuum emission from the broad-line region may contribute substantially to optical continuum variability and reverberation lags.

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“…Interestingly, Vincentelli et al (2022), together with Vincentelli et al (2021), observed an opposite trend in two intensive reverberation monitoring campaigns on Mrk 110. They divided two campaigns into three intervals based on X-ray luminosity, and found that the U-band lag excess is not observed in the lowest X-ray state but is seen in two subsequent intervals with higher X-ray luminosities, which indicates an opposite luminosity-dependent diffuse BLR lag in Mrk 110.…”

Section: Larger-than-expected Disk Sizementioning

confidence: 96%

Active Galactic Nuclei Continuum Reverberation Mapping Based on Zwicky Transient Facility Light Curves

Guo

¹

,

Barth

²

,

Wang

³

2022

ApJ

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We perform a systematic survey of active galactic nuclei (AGNs) continuum lags using ∼3 days cadence gri-band light curves from the Zwicky Transient Facility. We select a sample of 94 type 1 AGNs at z < 0.8 with significant and consistent inter-band lags based on the interpolated cross-correlation function method and the Bayesian method JAVELIN. Within the framework of the “lamp-post” reprocessing model, our findings are: (1) The continuum emission (CE) sizes inferred from the data are larger than the disk sizes predicted by the standard thin-disk model. (2) For a subset of the sample, the CE size exceeds the theoretical limit of the self-gravity radius (12 lt-days) for geometrically thin disks. (3) The CE size scales with continuum luminosity as R CE ∝ L 0.48±0.04 with a scatter of 0.2 dex, analogous to the well-known radius–luminosity relation of broad Hβ. These findings suggest a significant contribution of diffuse continuum emission from the broad-line region (BLR) to AGN continuum lags. We find that the R CE–L relation can be explained by a photoionization model that assumes ∼23% of the total flux comes from the diffuse BLR emission. In addition, the ratio of the CE size and model-predicted disk size anticorrelates with the continuum luminosity, which is indicative of a potential nondisk BLR lag contribution evolving with the luminosity. Finally, a robust positive correlation between the CE size and black hole mass is detected.

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The luminosity-dependent contribution from the broad-line region to the wavelength-dependent lags in Mrk 110

Cited by 18 publications

References 51 publications

Optical Continuum Reverberation in the Dwarf Seyfert Nucleus of NGC 4395

Optical Continuum Reverberation in the Dwarf Seyfert Nucleus of NGC 4395

Optical Continuum Reverberation in the Dwarf Seyfert Nucleus of NGC 4395

Active Galactic Nuclei Continuum Reverberation Mapping Based on Zwicky Transient Facility Light Curves

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