Talk detail

Participant	Arca Sedda, Manuel
Institution	Astronomisches Rechen Institut, ZAH-Heidelberg University - Monchhofstrasse 12-14 - Heidelberg - Baden-Wurttemberg - Germany

Session	GW1	Accepted	Yes	Order	6	Time	18:35	25'
Talk	Oral abstract	Title	Using merged BHs spins and masses to infer the formation history of their progenitors
Coauthors	Bemacquista, M.
Abstract	In this talk we investigate how the observed remnant masses and spins of merged black holes (BHs) can be used to constrain the progenitor binary black hole (BBH) formation history. Exploring different models, we found that the observed population of merged BHs is hard to reconcile with high-mass stellar BHs formed in metal poor environments. We find that if the LIGO sources were isolated BBHs, their components should have been characterised by mildly misaligned spins. The sources GW170104 and GW170814 may have formed through this channel. On another hand, a dynamical origin does a better job of explaining the origin of GW170608 and GW151226, likely formed from stars with nearly solar metallicities. Finally, we discuss the possibility that GW150914 may have originated from multiple merger events in a dense cluster.
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Session	BH2	Accepted	Yes	Order	8	Time	19:05	20'
Talk	Oral abstract	Title	Dancing in the dark: how to unveil a black hole subsystem sitting in the centre of a globular cluster
Coauthors	Askar, A. ; Giersz, M.
Abstract	In this talk, we discuss how globular clusters (GCs) structural and observational properties can be used to infer the presence of a black hole system (BHS) inhabiting their inner regions. We propose a novel way to identify the BHS size, defined as the GC radius containing a mass contributed equally from stars and stellar BHs. Using this definition, similar to the well-known concept of ``influence radius'', we found a ``fundamental plane'' connecting the BHS typical density with the GC central surface density profile, total luminosity and observational half-mass radius. Our approach allows us to define a unique way to connect the observational GCs parameters with their dark content. Comparing our results with observed Milky Way GCs, we found that many of them likely host, at the present time, as many as several hundreds of BHs. These BHS are characterized by a relatively low typical density, $\rho_\bhs \sim 10-10^5\Ms$ pc$^{-3}$ and composed of relatively massive BHs, with average masses in the range $m_\bhs = 14-22\Ms$. We showed also that a similar approach can be used to find Milky Way GCs potentially hosting an intermediate-mass black hole.
Pdf file