There are 40 billion billions of black holes in the universe

Date:
January 19, 2022
Source:
Scuola Internazionale Superiore di Studi Avanzati
Summary:
How many black holes are out there in the Universe? A new study
has investigated the demographics of stellar mass black holes,
which are black holes with masses between a few to some hundred
solar masses, that originated at the end of the life of massive
stars. According to the new piece of research, a remarkable amount
around 1% of the overall ordinary matter of the Universe is locked
up in stellar mass black holes.

Astonishingly, the researchers have found that the number of black
holes within the observable Universe (a sphere of diameter around
90 billions light years) at present time is about 40 trillions,
40 billion billions (i.e., about 40 x 1018, i.e. 4 followed by
19 zeros!).



FULL STORY ==========================================================================
How many black holes are out there in the Universe? This is one of
the most relevant and pressing questions in modern astrophysics and
cosmology. The intriguing issue has recently been addressed by the
SISSA Ph.D. student Alex Sicilia, supervised by Prof. Andrea Lapi and
Dr. Lumen Boco, together with other collaborators from SISSA and from
other national and international institutions. In a first paper of a
series just published in The Astrophysical Journal,the authors have investigated the demographics of stellar mass black holes, which are
black holes with masses between a few to some hundred solar masses, that originated at the end of the life of massive stars. According to the new research, a remarkable amount around 1% of the overall ordinary (baryonic) matter of the Universe is locked up in stellar mass black holes.

Astonishingly, the researchers have found that the number of black holes
within the observable Universe (a sphere of diameter around 90 billions
light years) at present time is about 40 trillions, 40 billion billions
(i.e., about 40 x 1018, i.e. 4 followed by 19 zeros!).


==========================================================================
A new method to calculate the number of black holes As the authors of
the research explain: "This important result has been obtained thanks
to an original approach which combines the state-of-the-art stellar and
binary evolution code SEVN developed by SISSA researcher Dr. Mario Spera
to empirical prescriptions for relevant physical properties of galaxies, especially the rate of star formation, the amount of stellar mass and the metallicity of the interstellar medium (which are all important elements
to define the number and the masses of stellar black holes). Exploiting
these crucial ingredients in a self-consistent approach, thanks to
their new computation approach, the researchers have then derived the
number of stellar black holes and their mass distribution across the
whole history of the Universe. Alex Sicilia, first author of the study, comments: "The innovative character of this work is in the coupling of
a detailed model of stellar and binary evolution with advanced recipes
for star formation and metal enrichment in individual galaxies. This is
one of the first, and one of the most robust, ab initio computation of
the stellar black hole mass function across cosmic history." Origin of
most massive stellar black holes The estimate of the number of black
holes in the observable Universe is not the only issue investigated
by the scientists in this piece of research. In collaboration with
Dr. Ugo Di Carlo and Prof. Michela Mapelli from University of Padova,
they have also explored the various formation channels for black holes
of different masses, like isolated stars, binary systems and stellar
clusters. According to their work, the most massive stellar black holes originate mainly from dynamical events in stellar clusters. Specifically,
the researchers have shown that such events are required to explain the
mass function of coalescing black holes as estimated from gravitational
wave observations by the LIGO/Virgo collaboration.

Lumen Boco, co-author of the paper, comments: "Our work provides a robust theory for the generation of light seeds for (super)massive black holes
at high redshift, and can constitute a starting point to investigate
the origin of 'heavy seeds', that we will pursue in a forthcoming paper.

Prof. Andrea Lapi, Sicilia's supervisor and coordinator of the Ph.D. in Astrophysics and Cosmology at SISSA, adds: "This research is really multidisciplinary, covering aspects of, and requiring expertise in stellar astrophysics, galaxy formation and evolution, gravitational wave and
multi- messenger astrophysics; as such it needs collaborative efforts
from various members of the SISSA Astrophysics and Cosmology group,
and a strong networking with external collaborators." Alex Sicilia's
work occurs in the context of an Innovative Training Network Project
"BiD4BESt -- Big Data Application for Black Hole Evolution Studies" co-
PIed by Prof. Andrea Lapi from SISSA (H2020-MSCAITN-2019 Project 860744),
that has been funded by the European Union with about 3.5 million Euros overall; it involves several academic and industrial partners, to provide
Ph.D. training to 13 early stage researchers in the area of black hole formation and evolution, by exploiting advanced data science techniques.

========================================================================== Story Source: Materials provided by Scuola_Internazionale_Superiore_di_Studi_Avanzati. Note: Content may be
edited for style and length.


========================================================================== Journal Reference:
1. Alex Sicilia, Andrea Lapi, Lumen Boco, Mario Spera, Ugo N. Di Carlo,
Michela Mapelli, Francesco Shankar, David M. Alexander, Alessandro
Bressan, Luigi Danese. The Black Hole Mass Function Across Cosmic
Times.

I. Stellar Black Holes and Light Seed Distribution. The
Astrophysical Journal, 2022; 924 (2): 56 DOI:
10.3847/1538-4357/ac34fb ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220119155213.htm

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