On the possibility that ultra-light boson haloes host and form supermassive black holes

Abstract

Several observations suggest the existence of super-massive black holes (SMBH) at the centers of giant galaxies. However the mechanism under which these objects form remains non completely understood. In this work we review an alternative mechanism of formation of galactic SMBHs. This is, the collapse of ultra-light scalar field configurations playing the role of dark matter halos. Several works have studied this scenario and investigated its plausibility. They demonstrate, by different techniques that a scalar field configuration with masses larger than 0.6 m 2 P l /m φ is able to form a black hole ( configurations made of ultra-light bosons with mass m φ ∼ 10 −22 eV /c 2 has a critical mass of collapse of 10 13 M ). I has been shown that the collapse into a SMBH occurs at a very slow rate, whilst the remaining forms the galactic halo and it is described by quasi-resonant solutions with cosmic lifetime. The theory of collapse of scalar field configurations into compact objects has been extensively studied in a full theoretical way mostly regarding to boson stars. In this work we extrapolate such results for models of galactic halos hosting central SMBHs. We construct the simplest setup of an ultralight scalar field configuration laying in a Schwarzschild space-time for modeling a galactic system with a SMBH in the quasi-static limit. This model is applicable to systems either out of their accretion-phase at late times or either for those undergoing into a very slow accretionphase, such as some early-type giant elliptic galaxies and bulges. On the other hand, very recent direct observation of Sagittarius A by the Event Horizon Telescope Ricarte & Dexter (2015) will open an era of explorations of the deep-inner galactic region of the Milky Way that will possible to test and distinguish various dark matter models. Thus we use our model to give a very first step towards that direction. We derive the stellar kinematics induced by this sort dark matter to obtain information of the black hole's influence into the observable features of the velocity field of visible matter deep inside the galaxy. Thus we compute the radial velocity, acceleration and velocity dispersion densities for some realistic cases.

Brief Review on Scalar Field Dark Matter Models

“…The masses of these SMBHs are in the range 10 4 − 10 6 M ⊙ , quite similar to the estimated 10 7 − 10 8 M ⊙ of the aforementioned soliton cores. Preliminary studies indicate a non-trivial interaction between black holes and scalar fields (Ureña-López and Liddle, 2002; Barranco and Bernal, 2011;Brito et al, 2017;Avilez et al, 2018), but so far it seems that there is not a significant absorption of the field for the values of the boson mass in the range 10 −22 −10 −21 eV, which are precisely of the most interest in cosmology and astrophysics.…”

Motion in time-periodic backgrounds with applications to ultralight dark matter halos at galactic centers

“…We should stress that our understanding of DM behaviour in the presence of the SMBH and during the galactic evolution timescales is still in its infancy and mostly focused on CDM [64,69] (but see also Refs. [10,13,26,70,71]). The core density estimate from Section V A may not apply in the sub-parsec region, since the SMBH can make the region denser, e.g.…”

Fuzzy dark matter soliton cores around supermassive black holes

“…Thus the impact of the SMBH on the density profile of the soliton merits study, and the exploration of this is the primary goal of our work. Scalar fields around black holes have been studied in a fully general relativistic context (Barranco et al 2017;Avilez et al 2018;Hui et al 2019), and seen to give rise to 'scalar wigs' surrounding the vicinity of 'no-hair' (2015) - 26 -25 -24 -23 -22 -21 -20 -19 -18 -17 -16 -26 -25 -24 -23 -22 -21 -20 -19 -18 -17 -16 Figure 1. Recent astrophysical constraints on FDM particle mass in the literature.…”