Journal article
Bondi or not Bondi: The impact of resolution on accretion and drag force modelling for Supermassive Black Holes
- Abstract:
- Whilst in galaxy-size simulations, supermassive black holes (SMBH) are entirely handled by sub-grid algorithms, computational power now allows the accretion radius of such objects to be resolved in smaller scale simulations. In this paper, we investigate the impact of resolution on two commonly used SMBH sub-grid algorithms; the Bondi-Hoyle-Lyttleton (BHL) formula for accretion onto a point mass, and the related estimate of the drag force exerted onto a point mass by a gaseous medium. We find that when the accretion region around the black hole scales with resolution, and the BHL formula is evaluated using local mass-averaged quantities, the accretion algorithm smoothly transitions from the analytic BHL formula (at low resolution) to a supply limited accretion (SLA) scheme (at high resolution). However, when a similar procedure is employed to estimate the drag force it can lead to significant errors in its magnitude, and/or apply this force in the wrong direction in highly resolved simulations. At high Mach numbers and for small accretors, we also find evidence of the advective-acoustic instability operating in the adiabatic case, and of an instability developing around the wake's stagnation point in the quasi-isothermal case. Moreover, at very high resolution, and Mach numbers above $\mathcal{M}_\infty \geq 3$, the flow behind the accretion bow shock becomes entirely dominated by these instabilities. As a result, accretion rates onto the black hole drop by about an order of magnitude in the adiabatic case, compared to the analytic BHL formula.
- Publication status:
- Published
- Peer review status:
- Peer reviewed
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(Preview, Version of record, pdf, 4.8MB, Terms of use)
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- Publisher copy:
- 10.1093/mnras/sty931
Authors
- Publisher:
- Oxford University Press
- Journal:
- Monthly Notices of the Royal Astronomical Society More from this journal
- Volume:
- 478
- Issue:
- 1
- Pages:
- 995–1016
- Publication date:
- 2018-04-18
- Acceptance date:
- 2018-04-11
- DOI:
- Keywords:
- Pubs id:
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pubs:828912
- UUID:
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uuid:f1656115-d6c5-4ce3-86c5-94a4e0100c4e
- Local pid:
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pubs:828912
- Source identifiers:
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828912
- Deposit date:
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2018-07-07
Terms of use
- Copyright holder:
- Slyz et al
- Copyright date:
- 2018
- Notes:
- © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices). This is the published version of the article. This is available online from Oxford University Press at: https://doi.org/10.1093/mnras/sty931
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