Michael Küffmeier (Marie Skłodowska-Curie global fellow)

Rejuvenating infall: an overlooked source of mass and angular momentum

Sigurd Jensen, Jaime Pineda, Paola Caselli (all MPE), Troels Haugbølle (NBI)

Let's go back in time to the year 2014

The classical picture

credit: M. Persson

star formation

planet formation

Is this the full picture?

Credit: ALMA (ESO/NAOJ/NRAO)

Ginski et al. 2021

Yen et al. 2019

Garufi et al. 2021

Pineda et al. 2020

50 au

see also:

BHB1 (Alves et al. 2020), GM Aur (Huang et al. 2021), IRS 63 (Segura-Cox in prep.), AB Aur (Grady et al. 1999 / Fukagawa et al. 2004), ...

Per-emb-50

Valdivia-Mena et al. 2022

Science question:

Can we get better (statistical) constraints on the relevance and importance of (late) infall from existing simulation data? 

Streamers: recall S. Heigl's talk

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

Late infall is common for stars*

 *unless they remain tiny

On average, stars with final masses of more than 1 solar mass accrete more than 50 % of their mass after 500 kyr

Note that some protostars still accrete after 1.2 Myr

Küffmeier, Jensen & Haugbølle '23

Origin of accreting gas

The accretion reservoir can extend beyond the core

(see also Smith+ 2011, Kuznetsova et al. 2020, Pelkonen+ 2021)

Two phase process:

Initial collapse followed by varying amount of post-collapse infall

Results:

Possibility of replenishing and refreshing the mass and chemical budget

Küffmeier, Jensen & Haugbølle '23

YSOs can appear younger than they really are

How old is the protostar?

Küffmeier, Jensen & Haugbølle '23

A poor analogy to a conference

Session start

Coffee break!

Streamers (and shadows?) as signs of infall

Formation of misaligned configuration

Observable as shadows in outer disk

Küffmeier, Dullemond, Reissl & Goicovic 2021

Ginski et al. 2021 (see also poster#32 by Labdon)

300 au

in agreement with Bate 2018

Summary

Pineda ... Küffmeier et al. 'Protostars and Planets VII'

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Segura-Cox et al. in prep.

Star & disk can be replenished by infall of initially unbound material

YSOs can be rejuvenated

talks by Bate, Price and Elsender; posters by Koumpia and Ambrose

talks by S. Federmann and M. Reiter

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

The connection to the larger scales

Küffmeier, Haugbølle & Nordlund 2017

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??)

"We find marginal relationships between disk sizes and M*." (Long+ 2022)

Küffmeier, Jensen & Haugbølle '23

Accretion of a binary system

zoom-in with maximum resolution of 3 AU; polytropic equation of state; ideal MHD

1000 au

Accretion of a binary system

Caveat: zoom-in with only maximum resolution of 3 AU; polytropic equation of state; ideal MHD; no radiative transfer (more to be done, but intriguing)

about 30 % of accreting mass goes through the star's own disk

almost 10 % of accreting mass of companion goes through the primary star's disk

Late infall happens more often than assumed

For solar mass stars ~50 % of final mass from beyond prestellar core! (Pelkonen et al. 2021)

Can disks be rejuvenated?

Küffmeier et al. 2022 in prep

Possibility of replenishing and refreshing the mass and chemical budget

It's fun to work on cosmic rays,

instead of catching Covid waves.

 Does cosmic-ray ionization play a crucial role in disk formation?

The connection to the larger scales

Küffmeier et al. 2017 / 2022 in prep.

Gas from beyond the prestellar core can fall onto the star-disk system

Simulate cloudlet infall onto disk

AREPO, pure hydrodynamical

R_{\rm i,d}=50\, \rm au
\Sigma(r) = 170 \left(\frac{\rm g}{\rm cm}\right)^{2} \left( \frac{r}{1 \rm au} \right)^{-3/2}
M_{\rm cloudlet}(R_{\rm cloudlet}) = 0.01 {\rm M}_{\odot} \left( \frac{R_{\rm cloudlet}}{5000 \rm au}\right)^{2.3}
R_{\rm cloudlet} = 887\, \rm au

isothermal gas

vary infalling angle

\alpha = 0^{\circ} (35^{\circ}, 60^{\circ}, 90^{\circ})
b = 1774\, \rm au

vary rotation (prograde, retrograde)

Küffmeier, Dullemond, Reißl, Goicovic et al. 2021

M_{*}=2.5\, \mathrm{M}_{\odot}

Outer disk forms around inner disk

Küffmeier et al. 2021

Prograde vs. retrograde infall

Retrograde infall causes:

  • counter-rotating inner and outer disk 
  • shrinking of inner disk
  • enhanced accretion
  • larger and deeper gap between disks

see also Vorobyov+ 2016

Küffmeier et al. 2021

Inner disk orientation

M_{\rm i, disk}=4 \ M_{\rm cloudlet}
M_{\rm cloudlet} = 1.87 \times 10^{-4} \ \mathrm{M}_{\odot}
M_{\rm i,disk} = 24 M_{\rm cloudlet}
M_{\rm i,disk}=4 \ M_{\rm cloudlet}
M_{\rm i,disk} = 0.4 \ M_{\rm cloudlet}

Küffmeier et al. 2021