Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session H14: Dynamical Formation of Binary Black HolesRecordings Available Undergrad Friendly
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Sponsoring Units: DAP Chair: Salvatore Vitale, Massachusetts Institute of Technology Room: Soho |
Sunday, April 10, 2022 10:45AM - 10:57AM |
H14.00001: Binary Black Hole mergers and galaxies' central black holes Antonella Palmese, Christopher Conselice, Maya Fishbach, James T Annis The origin of the binary black hole (BBH) mergers that LIGO/Virgo have detected is unclear, and it is likely that multiple formation mechanisms are at play. In this talk, I will present a new formation channel for LIGO/Virgo BBHs, which places such black holes at the center of very low mass dwarf galaxies. Another interesting possibility is that stellar mass BBHs merge around more massive central black holes, in Active Galactic Nuclei (AGN) disks. I will mention how both of these scenarios are relevant for to the most massive binary black hole merger detected to date, GW190521, and how confident associations and cosmological contraints can be placed with future gravitational wave detections and AGN catalogs or follow-up observations. |
Sunday, April 10, 2022 10:57AM - 11:09AM |
H14.00002: The Formation, Evolution, Destruction, and Gravitational-wave production of Star Clusters in a Milky Way-mass Galaxy Carl Rodriguez The formation of binary black holes is an urgent issue in gravitational-wave astrophysics. One particular scenario--dynamical formation in dense star clusters--has emerged as a leading candidate to explain many of LIGO/Virgo/KAGRA's detections, because of its robust predictions and limited number of uncertainties. But where do these dense clusters come from, and how is their evolution related to that of the galaxies that host them? I will describe a project combining cluster formation in a cosmological context with detailed N-body models of star clusters. Starting from collapsing giant molecular clouds in a Milky Way-mass galaxy simulation and informed by high-resolution models of cloud collapse and cluster formation, we create a catalog of young star clusters with masses, metallicities, ages, radii, concentrations, and tidal fields taken directly from the host galaxy. These clusters are then integrated forward to z=0 with our Cluster Monte Carlo Code, allowing us to model an entire system of star clusters in a Milky Way-mass galaxy. I will describe the binary black hole population formed by clusters and isolated binaries in this galaxy, and show how both populations and their observable properties are deeply linked to the evolutionary history of their host galaxy. |
Sunday, April 10, 2022 11:09AM - 11:21AM |
H14.00003: Dynamical evolution of young star clusters, runaway collisions, and massive black hole formation Kuldeep Sharma, Carl Rodriguez The radial surface brightness profiles of old star clusters, such as globular clusters, are typically fitted with the well-known King profile. However, such profiles do not appear to represent the young star clusters nearly as well. We study the evolution of the density profile of star clusters from an Elson in young massive clusters to a King profile in the later evolutionary stages. A compact star cluster with a flatter density profile has a higher dynamical interaction rate among its stars compared to a typical King profile. These dense young clusters can undergo collisional runaway mergers of stars forming intermediate-mass black holes (IMBHs), which cannot form through the stellar evolution of standalone stars. We present a suite of N-body simulations performed using the CMC cluster dynamics code across a grid of initial conditions in cluster metallicity, physical sizes, masses, and initial density profiles. We find that low metallicity, compact massive clusters are more efficient at forming IMBHs with masses M>200Μ?. We will discuss the specific regions of parameter space that facilitate the formation of these massive black holes and their implications for LIGO/Virgo. |
Sunday, April 10, 2022 11:21AM - 11:33AM |
H14.00004: Closing the gap in the black hole mass spectrum with new detections of intermediate-mass black holes Giacomo Fragione, Frederic A Rasio, Abraham Loeb, Bence Kocsis, Joseph Silk Very little is known about the formation, evolution, and demographics of intermediate-mass black holes (IMBHs). While the classical approach to prove their existence based on the use of optical and infrared data is limited to nearby systems, gravitational wave (GW) missions have the potential to shed light on IMBHs up to the distant Universe. IMBH sources are most likely to be produced in dense stellar environments, where IMBHs can form GW-emitting binaries through dynamical interactions with other compact objects. The intermediate mass-ratio inspiral of a stellar compact remnant into an IMBH is a potential target for multi-band detection, since LISA measurements will alert astronomers of an incoming merger detectable within the next few years by LIGO/Virgo/Kagra, Einstein Telescope, and Cosmic Explorer. I will discuss how the properties of the host stellar environment affect the IMBH dynamics and growth, and characterize the typical GW signal expected for current and upcoming missions, which offer for the first time the opportunity to demonstrate the existence of IMBHs beyond any reasonable doubt and to fill the gap in the BH-mass spectrum. The next decade may bring hundreds of events, promising a spectacular range of new science from stellar evolution to cosmology. |
Sunday, April 10, 2022 11:33AM - 11:45AM |
H14.00005: The Stability of a One Dimensional Gravitational Cluster Amador C Muriel Recent observations reporting 60 globular clusters or faint galaxies orbiting the Milky Way (J.D. Simon and M. Geha, Physics Today, November 2021) raise the issue of the stability of globular clusters. We begin a program of studying the evaporation of stars from clusters. To start modestly, we consider a simple one-dimensional gravitational cluster. Our analytic approach will use the first two terms of a six-term time evolution equation for the one-particle distribution function (A. Muriel, Results in Physics, 2016) using the gravitational pair potential in one dimension. The resulting expressions are interpreted to be the Vlassov collisionless regime. The density of the cluster as a function of position and time is calculated by integration over momentum. We will display the time evolution of the density for various initial conditions and comment on the stability of the cluster. With insight from this one dimensional model, we outline the analysis for a 3-d globular cluster with spherical symmetry, effectively one dimensional as well. |
Sunday, April 10, 2022 11:45AM - 11:57AM |
H14.00006: Never two without three: binary black hole mergers via three-body encounters in young, globular, and nuclear star clusters Marco Dall'Amico, Michela Mapelli Since the first detection of gravitational waves in 2015, the population of compact binary objects has grown year after year, counting now more than 60 confirmed binary black hole (BBH) mergers. With such a rapidly increasing population, more and more questions are arising. The detection of massive black holes (BH) in the 60-120 M⊙ mass range, the spin discrepancy with the BH population in X-ray binaries, and the observation of possible processing BBHs are only a few of these open issues that urgently seek an answer. In my talk, I will show how three-body encounters between BHs may represent a way out to solve this BH population puzzle. Three-body interactions are the most frequent kind of encounters that can take place between BHs inside crowded stellar environments. Starting from the results of my N-body simulations, I will present how these interactions differently affect the BH population of young, globular, and nuclear star clusters and what is their role in the formation of BBH mergers. The mass, spin, and eccentricity of the BH binaries are strongly influenced by these interactions and by the hosting environment. Different properties may therefore be used as fingerprints to derive the birthplace of these mergers from the observations, and to solve these still-open issues. |
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