Supermassive Black Holes, Ultralight Dark Matter, and Gravitational Waves from a First Order Phase Transition

There is controversy surrounding the origin and evolution of our universe's largest supermassive black holes (SMBHs). In this study, we consider the possibility that some of these black holes formed from the direct collapse of primordial density perturbations. Since the mass of a primordial black hole is limited by the size of the cosmological horizon at the time of collapse, these SMBHs must form rather late, and are naively in conflict with constraints from CMB spectral distortions. These limits can be avoided, however, if the distribution of primordial curvature perturbations is highly non-Gaussian. After quantifying the departure from Gaussianity needed to evade these bounds, we explore a model of multi-field inflation — a non-minimal, self-interacting curvaton model — which has all the necessary ingredients to yield such dramatic non-Gaussianities. We leave the detailed model building and numerics to a future study, however, as our goal is to highlight the challenges associated with forming SMBHs from direct collapse and to identify features that a successful model would need to have. This study is particularly timely in light of recent observations of high-redshift massive galaxy candidates by the James Webb Space Telescope as well as evidence from the NANOGrav experiment for a stochastic gravitational wave background consistent with SMBH mergers.

“…The prospect of primordial SMBHs from these mechanisms is discussed in ref. [36] and ref. [37], respectively.…”

Section: Jcap04(2024)021mentioning

confidence: 99%

Supermassive primordial black holes from inflation

Hooper,

Ireland,

Krnjaic

et al. 2024

“…A SMBH production mechanism relying on a first order phase transition has been recently advanced [99], which is in tension with heavy quasar superradiance bounds [83]. Our model instead avoids these bounds for large enough m a .…”

Section: Jcap02(2023)031mentioning

confidence: 99%

Catastrogenesis: DM, GWs, and PBHs from ALP string-wall networks

Gelmini

Simpson²,

Vitagliano³

2023

Axion-like particles (ALPs), a compelling candidate for dark matter (DM), are the pseudo Nambu-Goldstone bosons of a spontaneously and explicitly broken global U(1) symmetry. When the symmetry breaking happens after inflation, the ALP cosmology predicts the formation of a string-wall network which must annihilate early enough, producing gravitational waves (GWs) and primordial black holes (PBHs), as well as non-relativistic ALPs. We call this process catastrogenesis. We show that, under the generic assumption that the potential has several degenerate minima, GWs from string-wall annihilation at temperatures below 100 eV could be detected by future CMB and astrometry probes, for ALPs with mass from 10-16 to 106 eV. In this case, structure formation could limit ALPs to constitute a fraction of the DM and the annihilation would produce mostly “stupendously large” PBHs. For larger annihilation temperatures, ALPs can constitute 100% of DM, and the annihilation could produce supermassive black holes with a mass of up to 109 M ⊙ as found at the center of large galaxies. Therefore our model can solve two mysteries, the nature of the DM and the origin of these black holes.

“…Due to the intense gravitational field and instability mechanism such as superradiance, an axion cloud may be formed around a rotating BH [19][20][21]. It has been shown that the EHT observations can be used in order to constrain ultralight ALPs parameter space [22,23]. A cloud of ultralight bosons around BHs can be probed also through its gravitational-wave (GW) signatures [24,25] or through the study of the dynamics of SMBH [26].…”

Section: Introductionmentioning

confidence: 99%

Probing axions via light circular polarization and event horizon telescope

Shakeri

Hajkarim

2023

The impact of axion-like particles on the light polarization around the horizon of supermassive black hole (SMBH) is discussed in the light of the latest polarization measurement of the Event Horizon Telescope (EHT). We investigate different sources of the polarization due to axion interaction with photons and the magnetic field of SMBH. These can modify the linear and circular polarization parameters of the emitted light. We have shown that a significant circular polarization can be produced via the photon scattering from the background magnetic field with axions as off-shell particles. This can further constrain the parameter space of ultralight axion-like particles and their couplings with photons. The future precise measurements of circular polarization can probe the features of ultralight axions in the near vicinity of SMBH.