Black hole binary systems

From dynamics to accretion

M.Sc. Cristián Maureira-Fredes

Max-Planck-Institut für Gravitationsphysik
Leibniz Universität Hannover

Outline

  • Background and motivation
  • Projects
    • Stellar systems dynamics
    • The importance of how to accrete
    • How to form gaseous structures?
  • Conclusions

Background

Black holes

"The most exciting, yet unknown, region of space-time with an unimaginable strong gravitational effect".


NASA/JPL-Caltech
http://www.nasa.gov/mission_pages/nustar/multimedia/pia16695.html

Motivation

Gravitational Wave Astronomy

Motivation

Why binaries of black holes?

    A simple way to form a system able to emit a Gravitational Wave.

Motivation

How do we create a BH binary?

Stellar evolution
Stellar dynamics

Motivation

Stellar dynamics

  • Dense stellar systems (GC and GN)
    • $N\approx 10^{6-7} \star/\textrm{pc}^{3}$ (1 pc ~ 3.26 light-year)
  • Stellar black hole binaries from detections!

Motivation

Stellar dynamics - not that easy!

Just solving
this ~300 years old equation:

$$\ddot {\mathbf r}_i= -G \sum_{j=1,\,j \neq i}^{j=N} m_j \frac{\left({\mathbf r}_i - {\mathbf r}_j \right)} {\left|{\mathbf r}_i - {\mathbf r}_j\right|^3}$$
The N-body problem
(Newtonian gravity)

Motivation

Stellar dynamics - Schemes

Collisionless
  • Tree code $O(N\ log\ N)$,
    Barnes and Hut 1986
  • Fast multipole method $O(N)$ Greengard 1987

Goals of this thesis

From dynamics to accretion

  • Dynamical evolution of GCs and BHBs.
  • Writing a code from scratch.

Stellar systems dynamics

GraviDy, a GPU modular, parallel direct-summation N-body
integrator: dynamics with softening


C. Maureira-Fredes & P. Amaro-Seoane
Monthly Notices of the Royal Astronomical Society,
Volume 473, Issue 3, p.3113-3127.

Stellar systems dynamics

Introduction


GraviDyView - $N-$body visualisation tool
https://gravidy.xyz/include/gravidy-view.html

Stellar systems dynamics

Experiments - Performance

Stellar systems dynamics

Experiments - Verification

Stellar systems dynamics

Experiments - Core collapse representation

Stellar systems dynamics

Experiments - Core collapse

Stellar systems dynamics

Experiments - Softening impact

Stellar systems dynamics

Results

Code structure diagram.

Stellar systems dynamics

Summary

  • The softening is a critical parameter.
  • New $N-$body integrator.
    • Includes post-Newtonian expansion terms for binary evolution

Motivation

What about Gas?

Point-particles are an idealisation of the system.

Goals of this thesis

From dynamics to Accretion


  • Understanding the formation and evolution of BHBs

  • The importance of accretion
    • longer phase compared to the GW-driven,
    • decides of the orbital configuration,
    • and defines the priors for data analysis.

Artist impression accretion disc around the BH Gargantua.
(http://dneg.com)

The importance of how to accrete

Retrograde binaries of massive black holes
in circum-binary accretion discs.


P. Amaro-Seoane, C. Maureira-Fredes, M. Dotti & M. Colpi
Astronomy & Astrophysics,
Volume 591, id.A114, 12 pp.

The importance of how to accrete

Motivation

Galaxy Collision Animation
Author: James Webb Space Telescope (JWST) Date: 27 October 2010

The importance of how to accrete

Introduction

  • Co-rotating circum-binary discs.


  • Main considerations
    • counter-rotating is more interesting.
      • resonances are either absent or weak Nixon & Lubow 2015
      • gas remove more angular momentum

The importance of how to accrete

Initial setup

  • 2D simulations (Fargo)
    • hydrodynamical grid
  • 3D simulations (Gadget)
    • Smoothed-particle hydrodynamics (SPH)

The importance of how to accrete

Experiments - Accretion prescriptions


Roche Lobe* - Fixed radius - Bound.

The importance of how to accrete

Results - Circular orbit

The importance of how to accrete

Results - Eccentric orbit

The importance of how to accrete

Results - 2D/3D distance

The importance of how to accrete

Summary

  • The assumption of using Roche Lobe accretion
    • not suitable for all scenarios.

  • Accreting bound particles improves this issue, but:
    • additional physics to be taken into account.

Motivation

The origin of the gas: interacting galaxies

  • Structure formation (Modern Cosmology)
  • Types or mergers
    • Major
      • Mayer et al. 2007, Colpi et al. 2009, Colpi & Dotti 2011
    • Unequal
      • Callegari et al. 2009, 2011, Khan et al. 2012
    • Minor
      • Callegari et al. 2011, Khan et al 2012.

The Antennae galaxies (Chandra X-ray Observatory, Hubble Space Telescope and Spitzer Space Telescope)

But does gas really distribute
around SMBHB in the shape of a disc?

How to form gaseous structures?

Accretion of clumpy cold gas onto massive black hole binaries:
the challenging formation of extended circum-binary structures


C. Maureira-Fredes, F.G. Goicovic, P. Amaro-Seoane & A. Sesana
Monthly Notices of the Royal Astronomical Society | Volume 478, Issue 2, p1726-1748.


Accretion of clumpy cold gas onto massive black hole binaries:
a possible fast route to binary coalescence


F. G. Goicovic, C. Maureira-Fredes, A. Sesana, P. Amaro-Seoane & J. Cuadra
Monthly Notices of the Royal Astronomical Society | Accepted

How to form gaseous structures?

Motivation

Cuadra et al. 2009

How to form gaseous structures?

Introduction

  • There are two main ideas regarding accretion
    • in a coherent way (Dotti et al. 2010)
    • stochastically (King et al. 2005, King & Pringle 2006)
      • Observational evidence! Tremblay et al. 2016, Macagni et al. 2018

  • Accretion of single clouds
    • Dunhill et al. 2014, Goicovic et al. 2016, 2017

How to form gaseous structures?

Experiments - Initial Setup

How to form gaseous structures?

Experiments - Distribution

Run A

Run B

How to form gaseous structures?

Experiments - Scenario (RunA, mostly co-rotating)

How to form gaseous structures?

Results - Number of gas particles

How to form gaseous structures?

Results - Mass evolution

How to form gaseous structures?

Experiments - Results

How to form gaseous structures?

Results - Structures

How to form gaseous structures?

Summary

  • First time of multiple infalling clouds onto MBHBs simulation
  • Main findings
    • Difficult to form stable circum-binary structures
    • Counter-rotating rings
    • Mini-discs formation
    • Accretion on the MBHB
    • Post interaction relaxation
  • http://multipleclouds.xyz

Conclusions

Stellar dynamics is a well-defined way to form BHB

    1. Developed from scratch a direct-summation integrator with relativistic corrections
    2. Studied the impact of softening on the global evolution: dangerous
    3. By detecting GWs from BHs formed this way, we can reverse-engineer and subtract information about the host cluster, invisible to our old friend the photon.
    4. Estimation of the prior distribution of binaries of BHs: boost in data analysis algorithms

Conclusions

The role of gas in binaries

    1. The previous is an idealisation, in particular for SMBHBs
    2. Accretion of counter-rotating systems must be defined using my findings, otherwise you derive a wrong evolution of all orbital parameters
    3. Gas does not distribute of SMBHBs in the shape of a disc. This is the 0-th order assumption of hundreds of papers on this topic. I show the kind of architectures the gas follows in reality, which are far away from a disc.
    4. This has a crucial impact on the ulterior evolution of the binary when it detaches from the gas, so that the prior distribution would be radically different.

Acknowledgements

  • Deutsche Forschungsgemeinschaft (DFG)
    • Gravitational Wave Astronomy
    • Supermassive black holes, accretion discs, stellar dynamics and tidal disruptions
  • The AEI, but above all the IMPRS.

Black hole binary systems

From dynamics to accretion

M.Sc. Cristián Maureira-Fredes

Max-Planck-Institut für Gravitationsphysik
Leibniz Universität Hannover

Conclusions

    1. New $N-$body code + PN terms
    2. Impact of softening
    3. Feedback from GW detections
    4. Boost in data analysis algorithms

    1. Don't forget about the gas in SMBHB
    2. Accretion of counter-rotating systems
    3. Difficult to get a shape of a disc.
    4. Crucial impact for GW-driven phase.


Black hole binary systems - C. Maureira-Fredes