Emission Signatures From Sub-Parsec Binary Supermassive Black Holes. I. Diagnostic Power of Broad Emission Lines

Nguyen, Khai V.; Bogdanović, Tamara

doi:10.3847/0004-637x/828/2/68

Cited by 40 publications

(29 citation statements)

References 133 publications

(237 reference statements)

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“…Motivated by the described advances in observational searches for sub-parsec SMBHBs, Nguyen and Bogdanović (2016) have developed a semi-analytic model to describe spectral emission-line signatures of these systems. Based on this study, they find that the modeled profiles show distinct statistical properties as a function of the semimajor axis, mass ratio, eccentricity of the binary, and the degree of alignment of the triple disk system (including two mini-disks and a circumbinary disk).…”

Section: Radio Imaging Searches For Smbhbs With the Vlbimentioning

confidence: 99%

The quest for dual and binary supermassive black holes: A multi-messenger view

Rosa

Vignali

Bogdanović

et al. 2019

New Astronomy Reviews

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The quest for binary and dual supermassive black holes (SMBHs) at the dawn of the multi-messenger era is compelling. Detecting dual active galactic nuclei (AGN)-active SMBHs at projected separations larger than several parsecs-and binary AGN-probing the scale where SMBHs are bound in a Keplerian binary-is an observational challenge. The study of AGN pairs (either dual or binary) also represents an overarching theoretical problem in cosmology and astrophysics. The AGN triggering calls for detailed knowledge of the hydrodynamical conditions of gas in the imminent surroundings of the SMBHs and, at the same time, their duality calls for detailed knowledge on how galaxies assemble through major and minor mergers and grow fed by matter along the filaments of the cosmic web. This review describes the techniques used across the electromagnetic spectrum to detect dual and binary AGN candidates and proposes new avenues for their search. The current observational status is compared with the state-of-the-art numerical simulations and models for formation of dual and binary AGN. Binary SMBHs are among the loudest sources of gravitational waves (GWs) in the Universe. The search for a background of GWs at nHz frequencies from inspiralling SMBHs at low redshifts, and the direct detection of signals from their coalescence by the Laser Interferometer Space Antenna in the next decade, make this a theme of major interest for multi-messenger astrophysics. This review discusses the future facilities and observational strategies that are likely to significantly advance this fascinating field.

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Section: Radio Imaging Searches For Smbhbs With the Vlbimentioning

confidence: 99%

The quest for dual and binary supermassive black holes: A multi-messenger view

Rosa

Vignali

Bogdanović

et al. 2019

New Astronomy Reviews

Self Cite

201

123

View full text Add to dashboard Cite

show abstract

“…Alternatively, BSBH candidates may be identified by measuring the bulk radial velocity (RV) drifts as a function of time in quasar broad emission lines (e.g., Gaskell 1983;Bogdanović et al 2008;Gaskell 2010;Shen & Loeb 2010;Popović 2012;Bon et al 2012;Eracleous et al 2012;Decarli et al 2013;McKernan & Ford 2015;Nguyen & Bogdanović 2016;Simić & Popović 2016;Pflueger et al 2018), in analogy to RV searches for exoplanets (Figure 1). Only one of the two BHs in a BSBH is assumed to be active, powering its own broad-line region (BLR).…”

Section: Introductionmentioning

confidence: 99%

Constraining sub-parsec binary supermassive black holes in quasars with multi-epoch spectroscopy – III. Candidates from continued radial velocity tests

Guo

Liu

Shen

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Quasars whose broad emission lines show temporal, bulk radial velocity (RV) shifts have been proposed as candidate sub-parsec (sub-pc), binary supermassive black holes (BSBHs). We identified a sample of 16 BSBH candidates based on two-epoch spectroscopy among 52 quasars with significant RV shifts over a few rest-frame years. The candidates showed consistent velocity shifts independently measured from two broad lines (Hβ and Hα or Mg II) without significant changes in the broad-line profiles. Here in the third paper of the series, we present further third-and fourth-epoch spectroscopy for 12 of the 16 candidates for continued RV tests, spanning ∼5-15 yr in the quasars' rest frames. Cross-correlation analysis of the broad Hβ calibrated against [O III] λ5007 suggests that 5 of the 12 quasars remain valid as BSBH candidates. They show broad Hβ RV curves that are consistent with binary orbital motion without significant changes in the broad line profiles. Their broad Hα (or Mg II) lines display RV shifts that are either consistent with or smaller than those seen in broad Hβ. The RV shifts can be explained by a ∼0.05-0.1 pc BSBH with an orbital period of ∼40-130 yr, assuming a mass ratio of 0.5-2 and a circular orbit. However, the parameters are not well constrained given the few epochs that sample only a small portion of the hypothesized binary orbital cycle. The apparent occurrence rate of sub-pc BSBHs is 13±5% among all SDSS quasars, with no significant difference in the subsets with and without single-epoch broad line velocity offsets. Dedicated long-term spectroscopic monitoring is still needed to further confirm or reject these BSBH candidates.

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“…Decarli et al 2013), which may contaminate the velocity shift detections. A related method uses binary BH models to predict kinematic signatures of binarity in the broad lines (see Nguyen & Bogdanović 2016).…”

Section: Introductionmentioning

confidence: 99%

Searching for Binary Supermassive Black Holes via Variable Broad Emission Line Shifts: Low Binary Fraction

Wang

Greene

et al. 2017

ApJ

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Supermassive black hole binaries (SMBHs) are expected to result from galaxy mergers, and thus are natural byproducts (and probes) of hierarchical structure formation in the Universe. They are also the primary expected source of low-frequency gravitational wave emission. We search for binary BHs using time-variable velocity shifts in broad Mg ii emission lines of quasars with multi-epoch observations. First, we inspect velocity shifts of the binary SMBH candidates identified in Ju et al. (2013), using SDSS spectra with an additional epoch of data that lengthens the typical baseline to ∼ 10 yr. We find variations in the line-of-sight velocity shifts over 10 years that are comparable to the shifts observed over 1-2 years, ruling out the binary model for the bulk of our candidates. We then analyze 1438 objects with 8 yr median time baselines, from which we would expect to see velocity shifts > 1000 km s −1 from sub-pc binaries. We find only one object with an outlying velocity of 448 km s −1 , indicating, based on our modeling, that 1 per cent (the value varies with different assumptions) of SMBHs that are active as quasars reside in binaries with ∼ 0.1 pc separations. Binaries either sweep through these small separations rapidly or stall at larger radii.

show abstract

Emission Signatures From Sub-Parsec Binary Supermassive Black Holes. I. Diagnostic Power of Broad Emission Lines

Cited by 40 publications

References 133 publications

The quest for dual and binary supermassive black holes: A multi-messenger view

The quest for dual and binary supermassive black holes: A multi-messenger view

Constraining sub-parsec binary supermassive black holes in quasars with multi-epoch spectroscopy – III. Candidates from continued radial velocity tests

Searching for Binary Supermassive Black Holes via Variable Broad Emission Line Shifts: Low Binary Fraction

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