The local nanohertz gravitational-wave landscape from supermassive black hole binaries

Mingarelli, Chiara M. F.; Lazio, T. Joseph W.; Sesana, Alberto; Greene, Jenny E.; Ellis, Justin; Ma, Chung‐Pei; Croft, Steve; Burke-Spolaor, S.; Taylor, Stephen R.

doi:10.1038/s41550-017-0299-6

Cited by 155 publications

(176 citation statements)

References 58 publications

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“…The binary masses of the detected events range from ∼ 3 M to ∼ 60 M , which while interesting, will be dwarfed by supermassive massive black hole (SMBH) coalescence in the centres of galaxies. In the next decade, the low-frequency inspiral of the most massive SMBH binaries (SMBHBs), 10 8 M , is expected to be detected by Pulsar Timing Ar-E-mail: gogiya@uwaterloo.ca (GO) rays (PTA; Mingarelli et al 2017;Kelley et al 2018), while the final coalescence of SMBHs in the 10 4 − 10 7 M range will be accessible with the upcoming Laser Interferometer Space Antenna (LISA; Amaro-Seoane et al 2017), and is the subject of our study here.…”

Section: Introductionmentioning

confidence: 99%

Accelerated orbital decay of supermassive black hole binaries in merging nuclear star clusters

Ogiya

Hahn

Mingarelli

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The coalescence of supermassive black holes (SMBHs) should generate the strongest sources of gravitational waves (GWs) in the Universe. However, the dynamics of their coalescence is the subject of much debate. In this study, we use a suite of N-body simulations to follow the merger of two nuclear star clusters (NSCs), each hosting a SMBH in their centre. We find that the presence of distinct star clusters around each SMBH has important consequences for the dynamical evolution of the SMBH binary: (i) The separation between the SMBHs decreases by a few orders of magnitude in the first few Myrs by the combined effects of dynamical friction and a drag force caused by tidally stripped stars. In fact, this is a significant speedup for equal mass ratio binaries, and becomes extreme for unequal mass ratios, e.g. 1:10 or 1:100, which traditional dynamical friction alone would not permit to bind. (ii) The subsequent binary hardening is driven by the gravitational slingshots between the SMBH binary and stars, and also depends on the mass ratio between the SMBHs. Thus, with this additional drag force, we find that all SMBHs in our suite coalesce within a Hubble time. Given that about 50% of Milky Way sized galaxies host NSCs, our results are encouraging for upcoming GW observations with the Laser Interferometer Space Antenna -LISA -which will detect SMBH coalescence in the 10 4 − 10 7 M mass range.

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Section: Introductionmentioning

confidence: 99%

Accelerated orbital decay of supermassive black hole binaries in merging nuclear star clusters

Ogiya

Hahn

Mingarelli

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…Dual AGNs in advanced mergers represent the most observationally accessible progenitors of the SMBH binary phase, which likely produces the main source of gravitational waves (GWs) (Wyithe & Loeb 2003;Sesana et al 2004;Mingarelli et al 2017;Kelley et al 2017) detectable by Pulsar Timing Array campaigns (Verbiest et al 2016) and future spacedbased observations from the Laser Interferometer Space Antenna (LISA) (Amaro-Seoane et al 2017). However, SMBH binaries in realistic astrophysical environments can stall on parsec-scale orbits, resulting in merger timescales that exceed the age of the Universe.…”

Section: Introductionmentioning

confidence: 99%

A Triple AGN in a Mid-infrared Selected Late-stage Galaxy Merger

Pfeifle

Satyapal

Manzano-King

et al. 2019

ApJ

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The co-evolution of galaxies and the supermassive black holes (SMBHs) at their centers via hierarchical galaxy mergers is a key prediction of ΛCDM cosmology. As gas and dust are funneled to the SMBHs during the merger, the SMBHs light up as active galactic nuclei (AGNs). In some cases, a merger of two galaxies can encounter a third galaxy, leading to a triple merger, which would manifest as a triple AGN if all three SMBHs are simultaneously accreting. Using high-spatial resolution X-ray, near-IR, and optical spectroscopic diagnostics, we report here a compelling case of an AGN triplet with mutual separations <10 kpc in the advanced merger SDSS J084905.51+111447.2 at z = 0.077. The system exhibits three nuclear X-ray sources, optical spectroscopic line ratios consistent with AGN in each nucleus, a high excitation near-IR coronal line in one nucleus, and broad Paα detections in two nuclei. Hard X-ray spectral fitting reveals a high column density along the line of sight, consistent with the picture of late-stage mergers hosting heavily absorbed AGNs. Our multiwavelength diagnostics support a triple AGN scenario, and we rule out alternative explanations such as star formation activity, shock-driven emission, and emission from fewer than three AGN. The dynamics of gravitationally bound triple SMBH systems can dramatically reduce binary SMBH inspiral timescales, providing a possible means to surmount the "Final Parsec Problem." AGN triplets in advanced mergers are the only observational forerunner to bound triple SMBH systems and thus offer a glimpse of the accretion activity and environments of the AGNs prior to the gravitationally-bound triple phase.

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“…Unlike stellar mass binary black holes (which are advanced LIGO's primary targets, e.g., Abbott et al 2016) whose detection is largely limited to the local Universe, merging BSBHs would be detectable almost close to the edge of the observable Universe (e.g., Klein et al 2016). The more massive, low-redshift population (i.e., in the relatively nearby Universe) is being hunted by pulsar timing arrays (e.g., Zhu et al 2014 Guo et al 2016;Dvorkin & Barausse 2017;Kelley et al 2017b;Mingarelli et al 2017;Wang & Mohanty 2017;Aggarwal et al 2018;Holgado et al 2018;Sesana et al 2018), whereas the less massive, high-redshift population (i.e., in the earlier Universe) will be targeted by space-borne experiments in future (e.g., Babak et al 2011;.…”

Section: Introductionmentioning

confidence: 99%

Spectral energy distributions of candidate periodically variable quasars: testing the binary black hole hypothesis

Guo

Liu

Zafar

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Periodic quasars are candidates for binary supermassive black holes (BSBHs) efficiently emitting low frequency gravitational waves. Recently, ∼150 candidates were identified from optical synoptic surveys. However, they may be false positives caused by stochastic quasar variability given the few cycles covered (typically 1.5). To independently test the binary hypothesis, we search for evidence of truncated or gapped circumbinary accretion disks (CBDs) in their spectral energy distributions (SEDs). Our work is motivated by CBD simulations that predict flux deficits as cutoffs from central cavities opened by secondaries or notches from minidisks around both BHs. We find that candidate periodic quasars show SEDs similar to those of control quasars matched in redshift and luminosity. While seven of 138 candidates show a blue cutoff in the IR-optical-UV SED, which may represent CBDs with central cavities, the red SED fraction is similar to that in control quasars, suggesting no correlation between periodicity and SED anomaly. Alternatively, dust reddening may cause red SEDs. The fraction of extremely radio-loud quasars, i.e., blazars (with R > 100), is tentatively higher than that in control quasars (at 2.5σ). Our results suggest that, assuming most periodic candidates are robust, IR-optical-UV SEDs of CBDs are similar to those of accretion disks of single BHs, if the periodicity is driven by BSBHs; the higher blazar fraction may signal precessing radio jets. Alternatively, most current candidate periodic quasars identified from few-cycle light curves may be false positives. Their tentatively higher blazar fraction and lower Eddington ratios may both be caused by selection biases.

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The local nanohertz gravitational-wave landscape from supermassive black hole binaries

Cited by 155 publications

References 58 publications

Accelerated orbital decay of supermassive black hole binaries in merging nuclear star clusters

Accelerated orbital decay of supermassive black hole binaries in merging nuclear star clusters

A Triple AGN in a Mid-infrared Selected Late-stage Galaxy Merger

Spectral energy distributions of candidate periodically variable quasars: testing the binary black hole hypothesis

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