The central black hole in the dwarf spheroidal galaxy Leo I Not supermassive, at most an intermediate-mass candidate

Abstract

It has been recently claimed that a surprisingly massive black hole (BH) is present in the core of the dwarf spheroidal galaxy (dSph) Leo I. Based on integral field spectroscopy, this finding challenges the typical expectation of dSphs hosting BHs of intermediate-mass, since such a BH would better be classified as supermassive. Indeed, the analysis points toward Leo I harboring a BH with a lower mass limit exceeding a few $10^6{M}_{\odot }$ at $1\sigma$, and the no BH case excluded at 95\% significance. Such a value, comparable to the entire stellar mass of the galaxy, makes Leo I a unique system that warrants further investigations. Using equilibrium models based on distribution functions (DFs) depending on actions $f(\mathbf{J})$ coupled with the same integral field spectroscopy data and an extensive exploration of a very large parameter space, we demonstrate, within a comprehensive Bayesian framework of model-data comparison, that the posterior on the BH mass is flat towards the low-mass end and, thus, that the kinematics of the central galaxy region only imposes an upper limit on the BH mass of few $10^5{M}_{\odot }$ (at $3\sigma$). Such an upper limit brings back the putative BH of Leo I under the category of intermediate-mass BHs, and it is also in line with formation scenarios and expectations from scaling relations at the mass regime of dwarf galaxies.

Accepted for publication in A&A Letters

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Cited by in corpus (5)

• EDGE: Dark matter core creation depends on the timing of star formation
• Leo I: the classical dwarf spheroidal galaxy with the highest dark-matter density
• The tidal features of the classical Milky Way satellites: Expected in MOND but inconsistent with cold dark matter models
• Multi-component, axisymmetric dynamical models of dSphs based on distribution functions: inferences on dark matter and intermediate-mass black holes in Draco and Ursa Minor
• Distribution functions for spheroids