The Physics of Protoplanetesimal Dust Agglomerates. II. Low‐Velocity Collision Properties

Langkowski, Doreen; Teiser, Jens; Blum, Jürgen

doi:10.1086/525841

Cited by 59 publications

(70 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is much less than the collision velocity achieved in protoplanetary disks. Our estimation on u col,crit for silicate aggregates is consistent with several laboratory experiments and numerical simulations for silicate aggregates (e.g., Blum & Wurm 2000Langkowski et al 2008;Güttler et al 2010;Paszun & Dominik 2009;Seizinger & Kley 2013), suggesting the difficulty of silicate dust growth.…”

Section: Introductionsupporting

confidence: 89%

Growth efficiency of dust aggregates through collisions with high mass ratios

Wada

Tanaka

Okuzumi

et al. 2013

A&A

169

198

View full text Add to dashboard Cite

Context. Collisional growth of dust aggregates is an essential process in forming planetesimals in protoplanetary disks, but disruption through high-velocity collisions (disruption barrier) could prohibit the dust growth. Mass transfer through very different-sized collisions has been suggested as a way to circumvent the disruption barrier. Aims. We examine how the collisional growth efficiency of dust aggregates with different impact parameters depends on the size and the mass ratio of colliding aggregates. Methods. We used an N-body code to numerically simulate the collisions of different-sized aggregates. Results. Our results show that high values for the impact parameter are important and that the growth efficiency averaged over the impact parameter does not depend on the aggregate size, although the growth efficiency for nearly head-on collisions increases with size. We also find that the averaged growth efficiency tends to increase with increasing mass ratio of colliding aggregates. However, the critical collision velocity, above which the growth efficiency becomes negative, does not strongly depend on the mass ratio. These results indicate that icy dust can grow through high-velocity offset collisions at several tens of m s −1 , the maximum collision velocity experienced in protoplanetary disks, whereas it is still difficult for silicate dust to grow in protoplanetary disks.

show abstract

Section: Introductionsupporting

confidence: 89%

Growth efficiency of dust aggregates through collisions with high mass ratios

Wada

Tanaka

Okuzumi

et al. 2013

A&A

169

198

View full text Add to dashboard Cite

show abstract

“…This is a crucial assumption in which collisional outcomes like bouncing are a priori not possible because these do not take place at the low-N part of the simulations. Bouncing of aggregates is observed in laboratory experiments (Blum & Münch 1993;Blum 2006;Langkowski et al 2008;Weidling et al 2009), whereas it does not occur in our simulations. For silicates, bouncing occurs at sizes above approximately 100 μm (i.e., N > 10 9 particles) and is not fully understood from a microphysical perspective.…”

Section: B4 Limitations Of the Collision Recipecontrasting

confidence: 68%

Dust coagulation and fragmentation in molecular clouds

Ormel¹,

Paszun²,

Dominik³

et al. 2009

A&A

253

337

View full text Add to dashboard Cite

The cores in molecular clouds are the densest and coldest regions of the interstellar medium (ISM). In these regions ISM-dust grains have the potential to coagulate. This study investigates the collisional evolution of the dust population by combining two models: a binary model that simulates the collision between two aggregates and a coagulation model that computes the dust size distribution with time. In the first, results from a parameter study quantify the outcome of the collision -sticking, fragmentation (shattering, breakage, and erosion) -and the effects on the internal structure of the particles in tabular format. These tables are then used as input for the dust evolution model, which is applied to an homogeneous and static cloud of temperature 10 K and gas densities between 10 3 and 10 7 cm −3 . The coagulation is followed locally on timescales of ∼10 7 yr. We find that the growth can be divided into two stages: a growth dominated phase and a fragmentation dominated phase. Initially, the mass distribution is relatively narrow and shifts to larger sizes with time. At a certain point, dependent on the material properties of the grains as well as on the gas density, collision velocities will become sufficiently energetic to fragment particles, halting the growth and replenishing particles of lower mass. Eventually, a steady state is reached, where the mass distribution is characterized by a mass spectrum of approximately equal amount of mass per logarithmic size bin. The amount of growth that is achieved depends on the cloud's lifetime. If clouds exist on free-fall timescales the effects of coagulation on the dust size distribution are very minor. On the other hand, if clouds have long-term support mechanisms, the impact of coagulation is important, resulting in a significant decrease of the opacity on timescales longer than the initial collision timescale between big grains.

show abstract

“…Wada et al (2011) obtained similar results when performing molecular dynamics simulations of collisions of CPE aggregates featuring a hard sphere. Langkowski et al (2008) found that molding an aggregate significantly alters the outcome of a collision experiment. However, Kothe et al (2013) analyzed aggregates used in their collision experiments with X-ray computer tomography imaging and could not find any compacted outer layers.…”

Section: Discussionmentioning

confidence: 99%

Bouncing behavior of microscopic dust aggregates

Seizinger

Kley

2013

A&A

View full text Add to dashboard Cite

Context. Bouncing collisions of dust aggregates within the protoplanetary disk may have a significant impact on the growth process of planetesimals. Yet, the conditions that result in bouncing are not very well understood. Existing simulations studying the bouncing behavior used aggregates with an artificial, very regular internal structure. Aims. Here, we study the bouncing behavior of sub-mm dust aggregates that are constructed applying different sample preparation methods. We analyze how the internal structure of the aggregate alters the collisional outcome and we determine the influence of aggregate size, porosity, collision velocity, and impact parameter. Methods. We use molecular dynamics simulations where the individual aggregates are treated as spheres that are made up of several hundred thousand individual monomers. The simulations are run on graphic cards (GPUs). Results. Statistical bulk properties and thus bouncing behavior of sub-mm dust aggregates depend heavily on the preparation method. In particular, there is no unique relation between the average volume filling factor and the coordination number of the aggregate. Realistic aggregates bounce only if their volume filling factor exceeds 0.5 and collision velocities are below 0.1 ms −1 . Conclusions. For dust particles in the protoplanetary nebula we suggest that the bouncing barrier may not be such a strong handicap in the growth phase of dust agglomerates, at least in the size range of ≈100 µm.

show abstract

The Physics of Protoplanetesimal Dust Agglomerates. II. Low‐Velocity Collision Properties

Cited by 59 publications

References 28 publications

Growth efficiency of dust aggregates through collisions with high mass ratios

Growth efficiency of dust aggregates through collisions with high mass ratios

Dust coagulation and fragmentation in molecular clouds

Bouncing behavior of microscopic dust aggregates

Contact Info

Product

Resources

About