Revealing the intermediate-mass black hole at the heart of the dwarf galaxy NGC404 with sub-parsec resolution ALMA observations
Journal article, 2020

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 approximate to 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 approximate to 5 x 10(5) M-circle dot 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(-3.8)(+4.1) x 10(5) M-circle dot (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 massbulge 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.

ISM-galaxies: kinematics and dynamics

galaxies: individual: NGC 404-galaxies

galaxies: evolution

galaxies: elliptical and lenticular, cD

galaxies: dwarf


Timothy A. Davis

Cardiff University

Dieu D. Nguyen

National Institutes of Natural Sciences

Anil C. Seth

University of Utah

Jenny E. Greene

Princeton University

Kristina Nyland

US Naval Res Lab, 4555 Overlook Ave SW

Aaron J. Barth

University of California at Irvine (UCI)

Martin Bureau

Yonsei University

University of Oxford

Michele Cappellari

University of Oxford

Mark den Brok

Leibniz Institute for Astrophysics Potsdam

Satoru Iguchi

The Graduate University for Advanced Studies (SOKENDAI)

National Institutes of Natural Sciences

Federico Lelli

Cardiff University

Lijie Liu

University of Oxford

Nadine Neumayer

Max Planck Society


Cardiff University

Kyoko Onishi

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Extragalactic Astrophysics

Marc Sarzi

Annagh Observ & Planetarium

Mark D. Smith

University of Oxford

Thomas G. Williams

Max Planck Society

Monthly Notices of the Royal Astronomical Society

0035-8711 (ISSN) 1365-2966 (eISSN)

Vol. 496 4 4061-4078

Subject Categories

Subatomic Physics

Analytical Chemistry

Astronomy, Astrophysics and Cosmology



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