BHI Colloquium


Monday, April 11, 2022, 11:00am to 12:00pm


BHI Meeting room

Nico Cappelluti (Astronomy) - University of Miami

Title: The Early Universe in a PBH-ΛCDM Cosmology: How a simple solution might solve several difficult problems

Abstract: We explore the observational implications of a model in which primordial black holes (PBHs) with a broad birth mass function ranging in mass from a fraction of a solar mass to ∼10^6 solar masses, consistent with current observational limits, constitute the dark matter component in the Universe. The formation and evolution of dark matter and baryonic matter in this PBH- LambdaCDM Universe are presented. In this picture, PBH DM mini-halos collapse earlier than in standard LambdaCDM, baryons cool to form stars at z∼ 15−20, and growing PBHs at these early epochs start to accrete through Bondi capture. The volume emissivity of these sources peaks at z∼20 and rapidly fades at lower redshifts. As a consequence, PBH DM could also provide a channel to make early black hole seeds and naturally account for the origin of an underlying dark matter halo - host galaxy and central black hole connection that manifests as the Mbh−sigma correlation. To estimate the luminosity function and contribution to integrated emission power spectrum from these high-redshift PBH DM halos, we develop a Halo Occupation Distribution (HOD) model. In addition to tracing the star formation and reionizaton history, it permits us to evaluate the Cosmic Infrared and X-ray Backgrounds (CIB and CXB). We find that accretion onto PBHs/AGN successfully accounts for the detected backgrounds and their cross-correlation, with the inclusion of an additional IR stellar emission component. Detection of the deep IR source count distribution by the JWST could reveal the existence of this population of high-redshift star-forming and accreting PBH DM.

Bio: Nico is an assistant Professor at the Physics department of University of Miami. He is interested in employing wide field multiwavelength surveys for finding observational proxies of the formation mechanisms of Super Massive Black holes in the Universe, determining the origin of Cosmic Backgrounds, studying Active Galactic Nuclei clustering and investigate the nature of Dark Matter. He obtained his PhD through the International Max-Planck Research School (IMPRS) at the Technische Universität of Munich (TUM) in Germany, working on the COSMOS survey  at the Max Planck Institute for Extraterrestial Physics (MPE). He was the YCAA prize fellow at Yale University.


See also: Astronomy