HEP Colloquia 2024

by Filippo Santoliquido (Istituto Nazionale di Fisica Nucleare)

Friday 29 Nov 2024, 14:30 → 16:00 Europe/Rome

Sala Consiliare (Department of Physics)

Binary Black Holes mergers from Population III stars

Population III (Pop. III) stars, formed from pristine, metal-free gas in the aftermath of cosmic nucleosynthesis at redshift z > 20, are thought to have produced the Universe's first stellar-origin black holes. Binary Pop. III stars are likely responsible for the earliest binary black hole (BBH) mergers. In this seminar, I will explore the main uncertainties influencing the evolution of the merger rate density and mass spectrum of Pop. III BBHs. My analysis covers a broad range of parameters, including four different star formation histories. Depending on the rate of star formation, the peak merger rate density shifts from redshift z ~ 8 to as high as z ~ 16. For our fiducial binary population model, the maximum BBH merger rate density lies between 2 and 30 Gpc⁻³ yr⁻¹. Pop. III black holes tend to be significantly more massive (30–40 M⊙) compared to those born from metal-rich stars (8–10 M⊙). These early BBHs are prime candidates for detection by next-generation gravitational-wave observatories like the Einstein Telescope (ET). I will discuss the expected number of these high-redshift sources that ET could observe.