SDSS J0159 as an outlier in the <i>M</i>BH–σ space: further clues to support a central tidal disruption event?

Zhang, Xueguang; Bao, Min; Yuan, Qirong

doi:10.1093/mnrasl/slz151

“…A similar argument can be made for the TDE PS18kh (Holoien et al 2019). Although it has a larger BH mass (M BH ≈ 10 6.9 M e ) than 1ES 1927+654, its Hα line is also broader (FWHM = 12,000 km s −1 ), such that their dynamical timescales end up being roughly comparable: (Zhang et al 2019), the dynamical timescale of SDSS J015957.64+003310.5 is close to twice that of 1ES 1927+654, or ∼7 yr. This is roughly comparable to the 10 yr timescale over which velocity changes were detected.…”

Section: Comparison With Other Tdessupporting

confidence: 64%

The Host Galaxy and Rapidly Evolving Broad-line Region in the Changing-look Active Galactic Nucleus 1ES 1927+654

Li

¹

,

Ho

²

,

Ricci

³

et al. 2022

ApJ

View full text Add to dashboard Cite

Changing-look active galactic nuclei (AGNs) present an important laboratory to understand the origin and physical properties of the broad-line region (BLR). We investigate follow-up optical spectroscopy spanning ∼500 days after the outburst of the changing-look AGN 1ES 1927+654. The emission lines displayed dramatic, systematic variations in intensity, velocity width, velocity shift, and symmetry. Analysis of optical spectra and multiband images indicates that the host galaxy contains a pseudobulge and a total stellar mass of 3.56 − 0.35 + 0.38 × 10 9 M ⊙ . Enhanced continuum radiation from the outburst produced an accretion disk wind, which condensed into BLR clouds in the region above and below the temporary eccentric disk. Broad Balmer lines emerged ∼100 days after the outburst, together with an unexpected, additional component of narrow-line emission. The newly formed BLR clouds then traveled along a similar eccentric orbit (e ≈ 0.6). The Balmer decrement of the BLR increased by a factor of ∼4–5 as a result of secular changes in cloud density. The drop in density at late times allowed the production of He i and He ii emission. The mass of the black hole cannot be derived from the broad emission lines because the BLR is not virialized. Instead, we use the stellar properties of the host galaxy to estimate M BH = 1.38 − 0.66 + 1.25 × 10 6 M ⊙ . The nucleus reached near or above its Eddington limit during the peak of the outburst. We discuss the nature of the changing-look AGN 1ES 1927+654 in the context of other tidal disruption events.

show abstract

“…Similar to what we have previously done in Zhang (2014), Zhang & Feng (2016), Zhang et al (2019), and Zhang (2021a, 2021b to describe the stellar lights included in SDSS spectra of BLAGN, we here exploit a power-law component α × λ β applied to describe the AGN continuum emissions and the 39 simple stellar population templates from Bruzual & Charlot (2003), which include a population age from 5 Myr to 12 Gyr, with three solar metallicities (Z = 0.008, 0.05, and 0.02). Then, through the Levenberg-Marquardt least-squares minimization method applied to the SDSS spectra with both narrow and broad emission lines being masked out, host-galaxy Note.…”

Section: Main Procedures Main Results and Main Discussionmentioning

confidence: 99%

“…There are seven model parameters in the elliptical accretion disk model: the inner boundary r 0 and outer boundary r 1 , in the units of R G (Schwarzschild radius), the inclination angle i of disk-like BLRs, the eccentricity e, the orientation angle f 0 of the elliptical rings, the local broadening velocity σ L , and the line emissivity slope q ( f r ∝ r − q ). Meanwhile, we have also applied the very familiar elliptical accretion disk model; see our studies on double-peaked lines in Wang et al (2005), Zhang (2013aZhang ( , 2015, and Zhang et al (2019). More detailed descriptions on the applied elliptical accretion disk model can be found in Eracleous et al (1995), Storchi-Bergmann et al (2003), and Strateva et al (2003, and as such no further discussions on the elliptical accretion disk model are given in this paper.…”

Section: Main Hypotheses For Estimating Upper Limits Of Sizes Ofmentioning

confidence: 99%

Dependence of Narrow-line Region Sizes on [O iii] Luminosity in Low-redshift Active Galactic Nuclei with Double-peaked Broad Balmer Emission Lines

Zhang¹

2022

ApJS

12

0

View full text Add to dashboard Cite

In this paper, simple but interesting results are reported on the upper limits of narrow-line region (NLR) sizes of a small sample of 38 low-redshift (z < 0.1) active galactic nuclei (AGN) with double-peaked broad emission lines (double-peaked BLAGN), in order to check whether the NLR sizes in type-1 AGN (broad line) and type-2 AGN (narrow line) obey a similar empirical dependence on [O iii] luminosity. In order to correct the inclination effects on projected NLR sizes of type-1 AGN, the accretion disk origin is commonly applied to describe the double-peaked broad Hα line, leading to the determined inclination angles of central disk-like broad-line regions of 38 double-peaked BLAGN. Then, considering the fixed Sloan Digital Sky Survey (SDSS) fiber radius, the upper limits of the NLR sizes of the 38 double-peaked BLAGN can be estimated. Meanwhile, a strong linear correlation between continuum luminosity and [O iii] luminosity is applied to confirm that the [O iii] emissions of the 38 double-peaked BLAGN are totally covered in the SDSS fibers. Considering the reddening-corrected measured [O iii] luminosity, the upper limits of the NLR sizes of the 38 double-peaked BLAGN are within a 99.9999% confidence interval of the expected results from the empirical relation between NLR size and [O iii] luminosity in type-2 AGN. In the current understanding, there are no challenges to the unified model of AGN through the space properties of NLRs.

show abstract

“…The method above to measure stellar velocity dispersions through a single stellar template spectrum is not appropriate to determine host-galaxy contributions. More detailed descriptions of the SSP method can be found in Bruzual & Charlot (2003), Kauffmann et al (2003b), Cid Fernandes et al (2005), Cappellari (2017, and in our previous paper, Zhang (2014), Zhang & Feng (2016), Rakshit et al (2017), Zhang et al (2019), Zhang (2021Zhang ( , 2021aZhang ( , 2021b. Here, we do not show further detailed discussions on the SSP method any longer, but a simple description of the SSP method follows.…”

Section: Methods To Measure the Stellar Velocity Dispersionsmentioning

confidence: 99%

“…Woo et al (2015) reported a virial factor relative to the FWHM as the broad-line width, considering narrow-line Seyfert 1 galaxies. Moreover, considering reverberation-mapped broad-line AGNs, there are some improved M BH -σ relations with quite different slopes, from 3.25 to 6.34, for different samples of objects listed and discussed in Bennert et al (2015), Batiste et al (2017), Zhang et al (2019), and Bennert et al (2021), which should lead to different BH masses of Type 2 AGNs with different M BH -σ relations used.…”

Section: Introductionmentioning

confidence: 99%

Are There Larger Stellar Velocity Dispersions in Low-redshift Type 1 AGNs than in Type 2 AGNs?

Zhang

¹

2022

ApJS

View full text Add to dashboard Cite

The main objective of this article is to check the Unified Model (UM) for the expected similar stellar velocity dispersions between Type 1 and Type 2 active galactic nuclei (AGNs) and then to provide further clues on black hole (BH) mass properties. Unlike previous comparisons of BH masses estimated from M BH–σ relations for Type 2 AGNs and from virial BH masses for Type 1 AGNs, reliable stellar velocity dispersions σ measured from absorption features around 4000 Å are directly compared between the thus far largest samples of 6260 low-redshift (z < 0.3) Type 1 AGNs and almost all Type 2 AGNs in SDSS DR12. Although half of Type 1 AGNs do not have a measured σ due to unapparent absorption features overwhelmed by AGN activities, both properties of the mean spectra of Type 1 AGNs with and without a measured σ and a positive dependence of σ on the [O iii] luminosity can lead to a statistically larger σ for all Type 1 AGNs compared to the 6260 Type 1 AGNs with measured stellar velocity dispersions. Then, direct σ comparisons can lead to a statistically larger σ in Type 1 AGNs, with a confidence level higher than 10σ, after considering the necessary effects of different redshifts and different central AGN activities. Although Type 1 AGNs have a σ of only about (9 ± 3)% larger than Type 2 AGNs, the difference cannot be well explained at the current stage. Unless there is strong evidence to support different M BH–σ relations or to support quite different evolutionary histories between Type 1 and Type 2 AGNs, the statistically larger σ in Type 1 AGNs provides a strong challenge to the UM of AGNs.

show abstract

SDSS J0159 as an outlier in the MBH–σ space: further clues to support a central tidal disruption event?

Cited by 18 publications

References 42 publications

The Host Galaxy and Rapidly Evolving Broad-line Region in the Changing-look Active Galactic Nucleus 1ES 1927+654

The Host Galaxy and Rapidly Evolving Broad-line Region in the Changing-look Active Galactic Nucleus 1ES 1927+654

Dependence of Narrow-line Region Sizes on [O iii] Luminosity in Low-redshift Active Galactic Nuclei with Double-peaked Broad Balmer Emission Lines

Are There Larger Stellar Velocity Dispersions in Low-redshift Type 1 AGNs than in Type 2 AGNs?

Contact Info

Product

Resources

About