The nature of massive black hole binary candidates – I. Spectral properties and evolution

Decarli, Roberto; Dotti, Massimo; Fumagalli, Michele; Tsalmantza, P.; Montuori, C.; Lusso, Elisabeta; Hogg, David W.; Prochaska, J. Xavier

doi:10.1093/mnras/stt831

Cited by 57 publications

(69 citation statements)

References 49 publications

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“…We discussed details of these observations in Decarli et al (2013). Briefly, we adopted the T05 and T07 grisms on the blue and red arms respectively, providing spectral coverage in the ranges 3700-5000Å and 5500-11000Å, with a spectral resolution λ/∆λ ≈ 1300 (1 ′′ slit).…”

Section: Calar Alto Observationsmentioning

confidence: 99%

New insights on the recoiling/binary black hole candidate J0927+2943 via molecular gas observations

Decarli

Dotti

Mazzucchelli

et al. 2014

Monthly Notices of the Royal Astronomical Society

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The peculiar QSO J0927+2943 shows multiple sets of emission lines in its optical spectrum. This signature has been interpreted as the relative motion between a black hole, either recoiling or bound in a binary system, and its host galaxy, or as a superposition of two galaxies along the line of sight. In order to test these scenarios, we have collected 2mm CO(2-1) observations using the IRAM Plateau de Bure Interferometer, and optical images and spectroscopy at the Calar Alto observatory. Together with archival HST images, these data provide unique insights on the nature of this system. The recoiling/binary black hole scenarios are ruled out by the clear detection of a galactic-scale molecular gas reservoir at the same redshift of the QSO broad lines. The observations presented here also disfavour the superposition model, although with less constraints. Thus, the origin of the second, bright set of narrow emission lines in J0927+2943 is still unknown.

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Section: Calar Alto Observationsmentioning

confidence: 99%

New insights on the recoiling/binary black hole candidate J0927+2943 via molecular gas observations

Decarli

Dotti

Mazzucchelli

et al. 2014

Monthly Notices of the Royal Astronomical Society

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“…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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“…An examination of the observed emission-line profiles from SBHB candidates presented by Eracleous et al (2012), Decarli et al (2013), Liu et al (2014), and Li et al (2016), shows that these profiles can be asymmetric and offset, but are usually quite smooth and characterized by one or two peaks, unlike some of the profiles in our database with complex structure and up to sixpeaks. Admittedly, the fraction of profiles with such ahigh number of peaks is relatively small in our database and they are more common for eccentric binaries.…”

Section: Can Modeled Emission-line Profiles Be Compared To the Observmentioning

confidence: 81%

“…To address this ambiguity a new generation of spectroscopic searches has been designed to monitor the offset of the broad emission-line profiles over multiple epochs and target sources in which modulations in the offset are consistent with the binary orbital motion (Bon et al 2012;Eracleous et al 2012;Decarli et al 2013;Ju et al 2013;Liu et al 2014;Shen et al 2013;Li et al 2016). For example, Eracleous et al (2012) searched for < z 0.7 SDSS quasars whose broad b H lines are offset by  -1000 km s 1 and selected 88 quasars for observational followup from the initial group of ∼16,000 objects.…”

Section: Status Of Spectroscopic Searches For Sbhbsmentioning

confidence: 99%

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

Nguyen

Bogdanović

2016

ApJ

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Motivated by advances in observational searches for sub-parsec supermassive black hole binaries (SBHBs) made in the past few years, we develop a semi-analytic model to describe spectral emission-line signatures of these systems. The goal of this study is to aid the interpretation of spectroscopic searches for binaries and tohelp test one of the leading models of binary accretion flows in the literature: SBHB in a circumbinary disk. In this work, we present the methodology and a comparison of the preliminary model with the data. We model SBHB accretion flows as a set of three accretion disks: two mini-disks that are gravitationally bound to the individual black holes and a circumbinary disk. Given a physically motivated parameter space occupied by sub-parsec SBHBs, we calculate a synthetic database of nearly 15 million broad optical emission-line profiles and explore the dependence of the profile shapes on characteristic properties of SBHBs. We 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. This suggests that the broad emission-line profiles from SBHB systems can in principle be used to infer the distribution of these parameters and as such merit further investigation. Calculated profiles are more morphologically heterogeneous than the broad emission lines in observed SBHB candidates and we discuss improved treatment of radiative transfer effects, which will allow adirect statistical comparison of the two groups.

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The nature of massive black hole binary candidates – I. Spectral properties and evolution

Cited by 57 publications

References 49 publications

New insights on the recoiling/binary black hole candidate J0927+2943 via molecular gas observations

New insights on the recoiling/binary black hole candidate J0927+2943 via molecular gas observations

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

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

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