Modelling photoionisationfeedback with MCRT/MCRHD

From massive star formation to diffuse ionised gas

Bert Vandenbroucke (bert.vandenbroucke@ugent.be)

Tübingen Spring Workshop 2020 on Modeling High-Mass Stellar Feedback

Overview

Method: MCRT/MCRHD

Bondi accretionDiffuse Ionised Gas

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Method: MCRT/MCRHD

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CMacIonize

Regular (or AMR) grid

Voronoi grid

𝐼𝑖 = න𝜈𝑡

∞4𝜋𝐽𝑖 𝜈

ℎ𝜈𝜎 𝜈 d𝜈

≈𝑄

𝑊𝑡𝑉𝑖

𝑗

𝑤𝑗𝑙𝑖𝑗𝜎 𝜈𝑗

BV &Wood (2018)

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Iterative ionization state calculation

Iteratively repeat until convergence(takes approx. 10 iterations)

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Example output

Uniform HII region Turbulent HII region

based on Wood et al. (2013),BV & Sartorio (in prep.)

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Example output (2)

BV et al. (2018)

Hα emission in SILCC DR2

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Algorithmic improvements

2.0Domain-decomposed task-based MCRT

BV, in prep.

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Algorithmic improvements (2)

2.0

BV, in prep.

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MCRHD

Do hydro step

Convert quantities

Do MCRTUpdate

pressure

𝑇 = 𝑇𝑛𝑥𝐻 + 𝑇𝑖 1 − 𝑥𝐻

𝑇𝑛 = 500 K

𝑇𝑖 = 8,000 K

BV & Wood (2018)

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Bondi accretion

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1D Bondi accretion

Isothermal, steady-state accretiononto a point mass

𝑣 𝑟 =−𝐶𝑠 −𝑊−1 −𝜔 𝑟 , 𝑟 ≤ 𝑅𝐵

−𝐶𝑠 −𝑊0 −𝜔 𝑟 , 𝑟 > 𝑅𝐵

𝜔 𝑟 =𝑅𝐵𝑟

4

exp 3 −4𝑅𝐵𝑟

𝜌 𝑟 = −𝜌𝐵𝑅𝐵

2𝐶𝑠𝑟2𝑣 𝑟

Bondi (1952), BV et al. (2019)

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Trapped HII regions

Two-temperature isothermal steady-state accretion

Mestel (1954), Keto (2002,2003), BV et al. (2019)

A similar, closed-form analyticexpression is available

𝑑𝑃

𝑑𝑟< −

𝐺𝑀

𝑟2

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However…

See Lund et al. (2019), BV et al. (2019) for details

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Instability/numerical issue?Slide 21 of 29

3D accretion: D-type expansion in disk

Sartorio et al. (2019)

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3D accretion: trapped HII regions

Sartorio et al. (2019)

Non-spherical trapped and semi-trappedHII regions also possible

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Critical luminosity

Sartorio et al. (2019)

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Diffuse Ionised Gas

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Diffuse Ionised Gas (DIG)

WHAM survey (2003)Dettmar (1990)

Milky Way: WIMNGC 891

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Modelling DIG

Girichidis et al. (2016) BV et al. (2018)

UV radiationfrom O/B stars

SILCC DR2 DIG model

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RHD modelsIonising luminosity per source

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Discussion

MCRT/MCRHD as a method

not so slow as one might think

1D Bondi: instability vs numerical issue

can someone try this with another method?

The DIG as a constraint for feedback

need discs that have a diffuse gas layer to ionize

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