Magnetized Molecular Cloud Formation and Dynamics

Mordecai-Mark Mac Low Juan C. Ibáñez-Mejía

Joshua E. Wall Stephen McMillan Ralf S. Klessen

ESA/Herschel/PACS, SPIRE/Gould Belt survey Key Programme/Palmeirim et al. 2013

Ballesteros-Paredes+ 11

CO CS

Larson’s size-velocity relation has been argued to result from turbulent driving.

But, it only applies to a narrow range of column densities.

Ballesteros-Paredes+ 11

1/2 ]

normalization of Larson’s linewidth-size relation depends on column density

Modeling the turbulent ISM with FlashModel ingredients

20 k

pc

1 kpc

Gas self-gravity

Included at late times

Heating and coolingG0

T0 T1>T0

Ha

C+

C+

Ha

Ha

CO

CO

C+

C+

gstatic [pc / Myr2]

02.5

1.0

2.0

-2.5

-1.0

-2.0

random supernova & superbubbles

SN

SB

Magnetic fields

Ibáñez-Mejía + 16

Modeling the turbulent ISM with FlashMorphology

Ibáñez-Mejía et al. 2016

Modeling the turbulent ISM with FlashMorphology

Ibáñez-Mejía et al. 2016

Ibáñez-Mejía + 16

Ibáñez-Mejía + 16

Zooming-in to collapsing cloudsModel

1016

1017

1018

1019

1020

1021

Col

umn

dens

ity [

cm-2]

Δx = 0.06 pc

Δx = 0.12 pc Δx = 0.06 pc

Ibáñez-Mejía et al. 2017, in press, ArXiv:1705.01779

Evolution and collapse of a dense cloudResults

Ibáñez-Mejía et al. 2017, in press, ArXiv:1705.01779

Evolution and collapse of a dense cloudResults

Ibáñez-Mejía et al. 2017, in press, ArXiv:1705.01779

t = 0

Resolution study of energy: acceptable 25% variation

Ibáñez-Mejía et al. 2017, in press, ArXiv:1705.01779

1 pc

10 pc

100 pc

Ibáñez-Mejía, thesis & in prep +18M3e3

dx = 0.06 pc

Field angle varies Morphology

Dec

R. A.

20.7

21.6

22.5log10 (NH / cm -2)

b) c)

b) c)

Palmeirim et al. 2013, Narayanan et al., 2008, Ade et al. 2016. Planck XXXIII 2016Ibáñez-Mejía et al. 2018, in prep;

Field angle varies Morphology

Dec

R. A.

20.7

21.6

22.5log10 (NH / cm -2)

b) c)

b) c)

Ibáñez-Mejía et al. 2018, in prep;

blue data points from Crutcher +10

3

4 5

2

-1

10Ibáñez-Mejía, thesis, in prep +18

Dense clouds collapse quickly while accreting.Results

Ibáñez-Mejía et al. 2017, in press, ArXiv:1705.01779

Gravitational energy dominates cloud evolution.Results

Ibáñez-Mejía et al. 2017, in press, ArXiv:1705.01779

Contraction dominates over accretion for KE.Results

Ibáñez-Mejía et al. 2017, in press, ArXiv:1705.01779

Trans-Alfvénic envelope, super-Alfvénic coreResults

Cloud

Envelope

Ibáñez-Mejía et al. 2018, in prep

Histogram of relative orientations (HRO) between magnetic field and density gradient shows moderate alignment in envelope, none in core with n > 103 cm-3.

Ibáñez-Mejía, thesis & in prep +18

Soler+16

Crutcher+transitiondensity

Alfvénic Mach number inside and around a cloudResults

• Nearby SN feedback maintains the diffuse ISM super-Alfvénic.

• Cloud envelopes are mostly trans-Alfvénic to mildly super-Alfvénic.

• gravitational contraction drives fast, super-Alfvénic, motions inside the cloud

Cloud

Envelope

MA <1

MA ≈1

MA >1

Ibáñez-Mejía et al. 2018, in prep

Astrophysical MUlti-Purpose Software Environment

Wall, M-MML, McMillan, Klessen, Portegies-Zwart, in prep

Wall, M-MML, McMillan, Klessen, Portegies-Zwart, in prep

2400 AU resolution

104 M⊙

test cloud

Wall, M-MML, McMillan, Klessen, Portegies-Zwart, in prep

2400 AU resolution

104 M⊙

test cloud

Wall, M-MML, McMillan, Klessen, Portegies-Zwart, in prep

2400 AU resolution

104 M⊙

test cloud

Wall, M-MML, McMillan, Klessen, Portegies-Zwart, in prep

2000 AU resolution

103 M⊙

test cloud

Wall, M-MML, McMillan, Klessen, Portegies-Zwart, in prep

2000 AU resolution

103 M⊙

test cloud

Wall, M-MML, McMillan, Klessen, Portegies-Zwart, in prep

Wall, M-MML, McMillan, Klessen, Portegies-Zwart, in prep

Conclusionsconclusions

• In the absence of star formation and internal feedback, gravitational contraction seems to be the main driver of non-thermal motions inside dense clouds.

• Nearby SN explosions both compress the clouds’ envelopes, increasing mass accretion rates, and erode the surface and fragment the cloud.

• Gas flows around clouds are predominantly trans-Alfvénic, so magnetic fields play an active role regulating mass accretion rates.

• Magnetic fields inside dense clouds seem unable to prevent collapse. Hierarchical gravitational contraction drives super-Alfvénic internal motions.

• HII region expansion carries the field with it, but angle of observation matters.