Efficiency tests for estimating the gas and stellar population parameters in Type 2 objects

Bon, N.; Bon, E.

doi:10.1016/j.asr.2014.06.040

Cited by 8 publications

(16 citation statements)

References 45 publications

(52 reference statements)

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“…The fitting is implemented using the ULySS code 6 (Koleva et al 2009). More details of the spectral decomposition were described in Bon et al (2014Bon et al ( , 2016. Furthermore, Denissyuk et al (2015) collected spectroscopic monitoring data of Ark 120 over 1976-2013 using a 70-cm telescope.…”

Section: Hβ Profile Variationsmentioning

confidence: 99%

A Possible ∼20 yr Periodicity in Long-term Optical Photometric and Spectral Variations of the Nearby Radio-quiet Active Galactic Nucleus Ark 120

Wang

Zhang

et al. 2019

ApJS

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We study the long-term variability in the optical monitoring database of Ark 120, a nearby radio-quiet active galactic nucleus (AGN) at a distance of 143 Mpc (z = 0.03271). We compiled the historical archival photometric and spectroscopic data since 1974 and conducted a new two-year monitoring campaign in 2015-2017, resulting in a total temporal baseline over four decades. The long-term variations in the optical continuum exhibit a wave-like pattern and the Hβ integrated flux series varies with a similar behaviour. The broad Hβ profiles have asymmetric double peaks, which change strongly with time and tend to merge into a single peak during some epochs. The period in the optical continuum determined from various period-search methods is about 20 years and the estimated false alarm probability with null hypothesis simulations is about 1 × 10 −3 . The overall variations of the broad Hβ profiles also follow the same period. However, the present database only covers two cycles of the suggested period, which strongly encourages continued monitoring to track more cycles and confirm the periodicity. Nevertheless, in light of the possible periodicity and the complicated Hβ profile, Ark 120 is one candidate of the nearest radio-quiet AGNs with possible periodic variability and it is thereby a potential candidate host for a sub-parsec supermassive black hole binary. (15) the All-Sky Automated Survey for Supernovae database (Shappee et al. 2014; Kochanek et al. 2017). a The flux of [O III] λ5007 used for absolute calibration of spectra in the dataset. b The photometric data of all the datasets are at V -band, except for dataset M79 at B-band.c This dataset has no temporal overlap with the other datasets so that it is impossible to do intercalibration. We simply adjust the fluxes to make the mean and standard deviation to be at the same scales as those of the other datasets. We do not use this dataset for periodicity analysis.d This dataset includes 15 additional observations (50,863-52,282) that have not been public.e There is a large flux difference with respect to the other datasets. We offset the fluxes by −20.0 × 10 −15 erg s −1 cm −2 Å −1 before performing intercalibration.f This dataset has a poor temporal overlap with the other datasets and we simply fix ϕ = 1.

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Section: Hβ Profile Variationsmentioning

confidence: 99%

A Possible ∼20 yr Periodicity in Long-term Optical Photometric and Spectral Variations of the Nearby Radio-quiet Active Galactic Nucleus Ark 120

Wang

Zhang

et al. 2019

ApJS

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“…This is the first time the package has been used to analyze spectra of broad lines in AGNs, while before it was used for (i) determining stellar atmospheric parameters using the models of stellar atmosphere (Wu et al 2011) and (ii) studying the history of stellar populations (Bouchard et al 2010;Koleva et al 2011Koleva et al , 2013. Recently, Bon et al (2014) tested the accuracy of the code in recovering stellar population and gas parameters in Type 2 AGNs.…”

Section: Methods Of Analysismentioning

confidence: 99%

“…Since it is very difficult to fit stellar population in the spectra of Sy1 galaxies with broad emission lines, in the first step we fitted spectra of NGC 5548 in the minimum of activity with all free parameters of the model (defined with equation 3.1), and with multiplicative polynomials of the 15th order (as in Bon et al 2014). We find that a single stellar population with age of 7200 Myr and metallicity [Fe/H]=0.2 fits the best spectra in the minimum.…”

Section: Line and Continuum Fittingsmentioning

confidence: 99%

Evidence for Periodicity in 43 Year-Long Monitoring of NGC 5548

Bon¹,

Zucker²,

Netzer³

et al. 2016

ApJS

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113

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We present an analysis of 43 years (1972 to 2015) of spectroscopic observations of the Seyfert 1 galaxy NGC 5548. This includes 12 years of new unpublished observations (2003 to 2015). We compiled about 1600 Hβ spectra and analyzed the long-term spectral variations of the 5100Å continuum and the Hβ line. Our analysis is based on standard procedures, including the LombScargle method, which is known to be rather limited to such heterogeneous data sets, and a new method developed specifically for this project that is more robust and reveals a -2 -∼5700 day periodicity in the continuum light curve, the Hβ light curve, and the radial velocity curve of the red wing of the Hβ line. The data are consistent with orbital motion inside the broad emission line region of the source. We discuss several possible mechanisms that can explain this periodicity, including orbiting dusty and dust-free clouds, a binary black hole system, tidal disruption events, and the effect of an orbiting star periodically passing through an accretion disk.

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“…The very few works existing in this regard (e.g. Bon, Popović & Bon 2014;Hayward & Smith 2015;Ciesla et al 2015;) yield a variety of conclusions.…”

Section: Introductionmentioning

confidence: 99%

Impact of an AGN featureless continuum on estimation of stellar population properties

Cardoso

Gomes

Papaderos

2017

A&A

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The effect of the featureless power-law (PL) continuum of an active galactic nucleus (AGN) on the estimation of physical properties of galaxies with optical population spectral synthesis (PSS) remains largely unknown. With the goal of a quantitative examination of this issue, we fit synthetic galaxy spectra representing a wide range of galaxy star formation histories (SFHs) and including distinct PL contributions of the form F ν ∝ ν −α with the PSS code Starlight to study to which extent various inferred quantities (e.g. stellar mass, mean age, and mean metallicity) match the input. The synthetic spectral energy distributions (SEDs) computed with our evolutionary spectral synthesis code include an AGN PL component with 0.5 ≤ α ≤ 2 and a fractional contribution 0.2 ≤ x AGN ≤ 0.8 to the monochromatic flux at 4020 Å. At the empirical AGN detection threshold x AGN 0.26 that we previously inferred in a pilot study on this subject, our results show that the neglect of a PL component in spectral fitting can lead to an overestimation by ∼2 dex in stellar mass and by up to ∼1 and ∼4 dex in the light-and mass-weighted mean stellar age, respectively, whereas the light-and mass-weighted mean stellar metallicity are underestimated by up to ∼0.3 and ∼0.6 dex, respectively. These biases, which become more severe with increasing x AGN , are essentially independent of the adopted SFH and show a complex behaviour with evolutionary time and α. Other fitting set-ups including either a single PL or multiple PLs in the base reveal, on average, much lower unsystematic uncertainties of the order of those typically found when fitting purely stellar SEDs with stellar templates, however, reaching locally up to ∼1, 3 and 0.4 dex in mass, age and metallicity, respectively. Our results underscore the importance of an accurate modelling of the AGN spectral contribution in PSS fits as a minimum requirement for the recovery of the physical and evolutionary properties of stellar populations in active galaxies. In particular, this study draws attention to the fact that the neglect of a PL in spectral modelling of these systems may lead to substantial overestimates in stellar mass and age, thereby leading to potentially significant biases in our understanding of the co-evolution of AGN with their galaxy hosts.

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Efficiency tests for estimating the gas and stellar population parameters in Type 2 objects

Cited by 8 publications

References 45 publications

A Possible ∼20 yr Periodicity in Long-term Optical Photometric and Spectral Variations of the Nearby Radio-quiet Active Galactic Nucleus Ark 120

A Possible ∼20 yr Periodicity in Long-term Optical Photometric and Spectral Variations of the Nearby Radio-quiet Active Galactic Nucleus Ark 120

Evidence for Periodicity in 43 Year-Long Monitoring of NGC 5548

Impact of an AGN featureless continuum on estimation of stellar population properties

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