Michael Küffmeier (Carlsberg reintegration fellow)
On the role of infall on planet-forming disks
SU Aur
SU Aur
synthetic image
C. Granzow Holm, T. Haugbølle (NBI), J. Pineda (MPE), D. Segura-Cox (Rochester), S. Reißl, C. P. Dullemond (ITA)
Ginski et al. 2021
Krieger et al. 2021
History of modeling disk formation
spherical core collapse:
rotation
magnetization (mass-to-flux ratio)
non-ideal MHD effects
dust evolution
turbulence
useful for parameter studies
\rho(r) = \frac{\rho_{\rm c} R_{\rm c}^2}{R_{\rm c}^2 + r^2}
Bonnor-Ebert sphere
or uniform density
\rho(r) = \rho_{0}
What about magnetic fields?
Help! Where is the disk?!
Ohmic, Ambipolar, Hall
Turbulence
Santos-Lima et al. 2012
Hydro
ideal MHD
non-ideal MHD
turbulence + MHD
History of modeling disk formation
for more references, see Patrick Hennebelle's talk and review articles:
Wurster & Li 2018, Zhao et al. 2020, Tsukamoto et al. 2023, Küffmeier 2024
We did learn a lot from spherical collapse models.
It is not the full picture though.
Credit: ALMA (ESO/NAOJ/NRAO)
Ginski et al. 2021
Yen et al. 2019
Garufi et al. 2021
Pineda et al. 2020
50 au
BHB1 (Alves et al. 2020), GM Aur (Huang et al. 2021), IRS 63 (Podio et al. 2024, Segura-Cox in prep.), AB Aur (Grady et al. 1999 / Fukagawa et al. 2004), M512 Grant et al. 2021, Gupta et al. 2024, Cacciapuoti et al. 2024), PPVII review by Pineda et al. 2023, Antonio Garufi's talks
Per-emb-50
Valdivia-Mena et al. 2022 (see poster!)
Streamers:
Model star formation in a Molecular Cloud
isothermal magnetohydrodynamical (MHD) with driven turbulence
adaptive mesh refinement (AMR) simulations with RAMSES
maximum resolution: ≈25 au (level of refinement: 15), root grid about ≈1600 au (level 9)
Total mass: 3000 solar masses
periodic boundary conditions
altogether 321 sink particles at last snapshot (2 Myr after the formation of the first star)
simulation setup including detailed description of sink recipe presented in Haugbølle+2018
Küffmeier, Jensen & Haugbølle '23
Two phase accretion process
Initial collapse followed by varying amount of post-collapse infall
(see also Smith+ 2011, Padoan et al. 2020, Pelkonen+ 2021)
Küffmeier, Jensen & Haugbølle '23
Zoom-in on early phase
The cloud
Christian G. Holm
Poster in S19
Zoom-in on the cores
Christian G. Holm
similar approach as in Küffmeier et al. 2017
How does (early) infall shape disk formation?
Christian G. Holm
Zoom-in simulation with DISPATCH, ~1 au resolution in disk, barotropic equation of state
Visualizations: Berlok
Zoom-in on the forming disk
Christian G. Holm
Young embedded disks
Christian G. Holm
Zoom-in simulation with DISPATCH, ~1 au resolution in disk, barotropic equation of state
Poster in S19
Christian G. Holm
Infall fuels outflows
comparison of models (see also Lebreuilly et al. 2024) with observations (e.g., ALMA-DOT)
The post-collapse phase aka "late infall"
Post-collapse infall is common
On average, even solar mass stars gain ~50 % of their final mass through accretion of initially unbound material
Note that some protostars still accrete after 1.2 Myr
Küffmeier, Jensen & Haugbølle '23
(Pelkonen et al. 2021)
YSOs can appear younger than they really are
How old is the protostar?
Küffmeier, Jensen & Haugbølle '23
Class I
Class 0
Class II
Origin of accreting gas
"In the case of the more massive stars, accretion from the environment outside the original core volume is even more important than that from the core itself. [...]
The assumption of spherical symmetry cannot be applied to the majority of collapsing cores, and is never a good description of how stars accrete gas from outside the original core radius."
(Smith et al. 2011)
Spreading vs wind-driven?
Manara et al. 2023
Caveat!
Infall matters. Disks can easily be wind-driven and yet grow in size through infall of gas with high angular momentum.
Long et al. 2022
?
Angular momentum budget
- Large scatter of ang. mom.
- Increasing specific angular momentum for increasing final stellar mass
Specific angular momentum computed from all accreting tracer particles at the first snapshot after star formation
- subtle correlation with mass (inherited by disks?), important for WG7 (Miguel Vioque's talks)
"We find marginal relationships between disk sizes and M*." (Long+ 2022)
Küffmeier, Jensen & Haugbølle 2023
Long et al. 2022
see also recent papers by Padon et al. 2024, Winter et al. 2024
On average, stars with increasing final mass undergo prolonged infall
Orientation of star-disk systems can change substantially
Orientation of infall
Küffmeier, Haugbølle, Pineda & Segura-Cox 2024
How to quantify anisotropy of accretion?
FA = 0: perfectly isotropic accretion
FA = 1: maximally anisotropic accretion
Küffmeier, Haugbølle, Pineda & Segura-Cox 2024
Fractional anisotropy based on tracer particles
Post-collapse infall is more anisotropic than initial collapse
Post-collapse accretion phase resembles Bondi-Hoyle
Post-collapse infall is more anisotropic than initial collapse
Anisotropic accretion
FA = 0: perfectly isotropic accretion
FA = 1: maximum anisotropic accretion
Küffmeier, Haugbølle, Pineda & Segura-Cox 2024
Late infall is more anisotropic than early collapse
\mathrm{FA} = \sqrt{ \frac{1}{2}} \frac{\sqrt{(\lambda_1 - \lambda_2)^2 + (\lambda_2 - \lambda_3)^2 + (\lambda_3 - \lambda_1)^2}}{\sqrt{\lambda_1^2 + \lambda_2^2 + \lambda_3^2}}
Fractional anisotropy (FA) serves as a good measure for the (an-)isotropy of accretion.
FA=0: perfectly isotropic accretion, FA=1: maximally anisotropic
\frac{\Delta t_{\rm single}}{\Delta t_{\rm single}+\Delta t_{\rm mult}}
1
0
FA can also be a useful measure to compare (an)isotropy of stellar spins in clusters
Streamers (and shadows) as signs of infall
Formation of misaligned configuration
Observable as shadows in outer disk
Küffmeier, Dullemond, Reissl & Goicovic 2021
SU Aur (Ginski et al. 2021)
300 au
Krieger, Küffmeier et al. 2024
Do we really know disk "lifetimes"?
Polnitzky et al. 2024 in prep
Fraction reflecting occurrence of infall events instead of disk age?
Summary
Disks are replenished, distorted or even destroyed by misaligned infall
Protostellar environment and multiplicity matters
Star formation is a two-phase process consisting of mandatory initial collapse and post-collapse infall phase
Küffmeier 2024, credit: Lützen
(although barely covered in this talk)
Planet-forming disks are not isolated entities
- Is the disk solely replenished with fresh material?
- Does infall frequently lead to the formation of a new misaligned outer disk (and if yes, for how long)?
- Is (late) infall catastrophic? Does a completely new disk form?
Some questions to be addressed in upcoming work
Effect of ionization on disk size
increasing ionization rate
enhanced magnetic braking
smaller disks
see also Wurster et al. 2018
Küffmeier, Zhao & Caselli 2020
What fraction of the gas and dust returns to the disk after being ejected by an outflow?
Key question
Credit: Tsukamoto et al. 2021
"Ash-fall" scenario aka conveyor belt
Increase in dust-to-gas ratio because dust can grow in disk and return
Tsukamoto et al. 2021
Zoom-in on embedded stars
Küffmeier et al.
2019
Küffmeier et al. 2018
Küffmeier, Reißl et al. 2020
bridge structure similar to IRAS 16293--2422 (e.g. Sadavoy+ 2018, van der Wiel+ 2019, Maureira+ 2020)
~1500 AU
Pro: self-consistent initial and boundary conditions for star formation
Con: computationally more expensive, more difficult analysis
for a similar concept, see also Lebreuilly et al. 2024
Christian G. Holm
star A, t = 13 kyr
star A, t = 25 kyr
strong magnetic braking,
strong outflow
Gas accretes through the disk (little polar accretion)
Christian G. Holm
How do outflows affect disk formation?
star A, t = 13 kyr
star A, t = 25 kyr
strong magnetic braking,
strong outflow
Prospect to compare with observations of outflows (e.g., ALMA-DOT, PI: Podio)
Credit: NASA/ESA Hubble space telescope &
ALMA (ESO/NAOJ/NRAO)
The big challenge:
link planet to star formation
50 au
Implications for Al-26 heterogeneity
Küffmeier et al. 2016
- Gas is well-mixed within core, and hence Al-26 abundance is fixed during CAI formation (t<~100 kyr).
- BUT: significant deviations in Al-26 abundance beyond the core may likely be imprinted on disk afterwards!
Christian G. Holm
How do infall and outflow affect the disk?
Angular momentum transport via magnetic braking
Zoom-in on embedded protostars
Küffmeier, Calcutt & Kristensen 2019
bridge structure similar to IRAS 16293--2422 (e.g. Sadavoy+ 2018, van der Wiel+ 2019, Maureira+ 2020)
Küffmeier, Reißl et al. 2020
~1500 AU
Küffmeier et al. 2018
magnetohydrodynamics
\frac{\partial \mathbf{B}}{\partial t} = \nabla\times (\mathbf{v}\times\mathbf{B})
ideal MHD
\color{red}-\nabla\times[\eta_{\rm O} (\nabla \times \mathbf{B})]
\color{purple}-\nabla\times \{\eta_{\rm H} [(\nabla \times \mathbf{B}) \times \mathbf{B}/B] \}
\color{blue}-\nabla\times \{\eta_{\rm AD} \mathbf{B}/B \times [(\nabla \times \mathbf{B}) \times \mathbf{B}/B] \}
Ohmic dissipation
Hall
ambipolar diffusion
Non-ideal
COST kick-off: On the role of infall on planet-forming disks
By kuffmeier
