Surprisingly Strong K-band Emission Found in Low-luminosity Active Galactic Nuclei

Dumont, Antoine; Seth, Anil; Strader, Jay; Greene, Jenny E.; Burtscher, L.; Neumayer, Nadine

doi:10.3847/1538-4357/ab5798

Cited by 9 publications

(6 citation statements)

References 94 publications

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“…Various physical mechanisms could be causing this extended continuum emission. The centrally-concentrated flux around the black hole overlaps with hot dust emission (≈950 K) observed in the near infrared (Seth et al 2010;Dumont et al 2020), the extended Hα source visible in Figure 3, and the small radio jet. We consider it likely that the majority of this emission is from the Rayleigh-Jeans tail of the dust continuum, as its flux is far higher than the pure-synchrotron extrapolation of the jet spectral energy distribution Figure 13.…”

Section: Continuum Emissionmentioning

confidence: 67%

Revealing the intermediate-mass black hole at the heart of the dwarf galaxy NGC 404 with sub-parsec resolution ALMA observations

Davis

Nguyen

Seth

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We estimate the mass of the intermediate-mass black hole at the heart of the dwarf elliptical galaxy NGC 404 using Atacama Large Millimetre/submillimetre Array (ALMA) observations of the molecular interstellar medium at an unprecedented linear resolution of ≈0.5 pc, in combination with existing stellar kinematic information. These ALMA observations reveal a central disc/torus of molecular gas clearly rotating around the black hole. This disc is surrounded by a morphologically and kinematically complex flocculent distribution of molecular clouds, that we resolve in detail. Continuum emission is detected from the central parts of NGC 404, likely arising from the Rayleigh–Jeans tail of emission from dust around the nucleus, and potentially from dusty massive star-forming clumps at discrete locations in the disc. Several dynamical measurements of the black hole mass in this system have been made in the past, but they do not agree. We show here that both the observed molecular gas and stellar kinematics independently require a ≈5 × 105 M⊙ black hole once we include the contribution of the molecular gas to the potential. Our best estimate comes from the high-resolution molecular gas kinematics, suggesting the black hole mass of this system is 5.5$^{+4.1}_{-3.8}\times 10^5$ M⊙ (at the 99 per cent confidence level), in good agreement with our revised stellar kinematic measurement and broadly consistent with extrapolations from the black hole mass–velocity dispersion and black hole mass–bulge mass relations. This highlights the need to accurately determine the mass and distribution of each dynamically important component around intermediate-mass black holes when attempting to estimate their masses.

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Section: Continuum Emissionmentioning

confidence: 67%

Revealing the intermediate-mass black hole at the heart of the dwarf galaxy NGC 404 with sub-parsec resolution ALMA observations

Davis

Nguyen

Seth

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…With the launch of JWST, a better census of NSCs in higher mass galaxies will be possible through high-resolution mid-infrared observations of dusty galaxy cores. Also, the identification of faint AGN enabled by JWST will aid in understanding the frequency of black hole/NSC co-existence in lower mass galaxies (e.g., Dumont et al 2019). LSST will also play an important role in characterizing the population of black holes in low-mass galaxies through statistics on tidal disruption events, and variability of AGN (e.g., Baldassare et al 2018).…”

Section: Nscs As Gravitational-wave Emittersmentioning

confidence: 99%

Nuclear star clusters

Neumayer

Seth

Böker³

2020

Astron Astrophys Rev

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289

270

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We review the current knowledge about nuclear star clusters (NSCs), the spectacularly dense and massive assemblies of stars found at the centers of most galaxies. Recent observational and theoretical works suggest that many NSC properties, including their masses, densities, and stellar populations, vary with the properties of their host galaxies. Understanding the formation, growth, and ultimate fate of NSCs, therefore, is crucial for a complete picture of galaxy evolution. Throughout the review, we attempt to combine and distill the available evidence into a coherent picture of NSC evolution. Combined, this evidence points to a clear transition mass in galaxies of $$\sim 10^9\,M_\odot$$ ∼ 10 9 M ⊙ where the characteristics of nuclear star clusters change. We argue that at lower masses, NSCs are formed primarily from globular clusters that inspiral into the center of the galaxy, while at higher masses, star formation within the nucleus forms the bulk of the NSC. We also discuss the co-existence of NSCs and central black holes, and how their growth may be linked. The extreme densities of NSCs and their interaction with massive black holes lead to a wide range of unique phenomena including tidal disruption and gravitational-wave events. Finally, we review the evidence that many NSCs end up in the halos of massive galaxies stripped of the stars that surrounded them, thus providing valuable tracers of the galaxies’ accretion histories.

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“…The K-band continuum of AGN can present a strong contribution of hot dust emission from the inner border of the torus (e.g. Riffel et al 2009c;Dumont et al 2020). This component is present in about 90 per cent of Seyfert 1 nuclei, while only about 25 per cent of Seyfert 2 nuclei present this component (Riffel et al 2009b).…”

Section: H2 Vibrational and Rotational Temperaturesmentioning

confidence: 99%

The AGNIFS survey: distribution and excitation of the hot molecular and ionized gas in the inner kpc of nearby AGN hosts

Riffel

Storchi‐Bergmann

Riffel

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We use the Gemini NIFS instrument to map the H2 2.1218 μm and Brγ flux distributions in the inner 0.04–2 kpc of a sample of 36 nearby active galaxies (0.001 ≲ z ≲ 0.056) at spatial resolutions from 4 to 250 pc. We find extended emission in 34 galaxies. In ∼55 per cent of them, the emission in both lines is most extended along the galaxy major axis, while in the other 45 per cent the extent follows a distinct orientation. The emission of H2 is less concentrated than that of Brγ, presenting a radius that contains half of the flux 60 per cent greater, on average. The H2 emission is driven by thermal processes – X-ray heating and shocks – at most locations for all galaxies, where $0.4<\rm H_2/Br\gamma <6$. For regions where H2/Brγ > 6 (seen in 40 per cent of the galaxies), shocks are the main H2 excitation mechanism, while in regions with H2/Brγ < 0.4 (25 per cent of the sample) the H2 emission is produced by fluorescence. The only difference we found between type 1 and type 2 AGN was in the nuclear emission-line equivalent widths, that are smaller in type 1 than in type 2 due to a larger contribution to the continuum from the hot dusty torus in the former. The gas masses in the inner 125 pc radius are in the range 101 − 104 M⊙ for the hot H2 and 103 − 106 M⊙ for the ionised gas and would be enough to power the AGN in our sample for 105 − 108 yr at their current accretion rates.

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Surprisingly Strong K-band Emission Found in Low-luminosity Active Galactic Nuclei

Cited by 9 publications

References 94 publications

Revealing the intermediate-mass black hole at the heart of the dwarf galaxy NGC 404 with sub-parsec resolution ALMA observations

Revealing the intermediate-mass black hole at the heart of the dwarf galaxy NGC 404 with sub-parsec resolution ALMA observations

Nuclear star clusters

The AGNIFS survey: distribution and excitation of the hot molecular and ionized gas in the inner kpc of nearby AGN hosts

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