Ionization: a possible explanation for the difference of mean disk sizes in star-forming regions

Küffmeier, M.; Zhao, Bo; Caselli, P.

doi:10.1051/0004-6361/201937328

Cited by 42 publications

(33 citation statements)

References 100 publications

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“…These authors suggest the local cloud environment could have a substantial effect on the disk masses in a given region. For example, Kuffmeier et al (2020) find that ionization can decrease disk size: disks may be "born" with smaller masses in star-forming regions with higher ionization rates. Figure 6 plots the locations of the Ophiuchus BDs in this sample along with the locations of the TTS disks from Williams et al (2019).…”

Section: Discussionmentioning

confidence: 99%

Disk Masses and Dust Evolution of Protoplanetary Disks Around Brown Dwarfs

Rilinger,

Espaillat

2021

Preprint

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We present the largest sample of brown dwarf (BD) protoplanetary disk spectral energy distributions modeled to date. We compile 49 objects with ALMA observations from four star-forming regions: ρ Ophiuchus, Taurus, Lupus, and Upper Scorpius. Studying multiple regions with various ages enables us to probe disk evolution over time. Specifically, from our models we obtain values for dust grain sizes, dust settling, and disk mass; we compare how each of these parameters vary between the regions. We find that disk mass decreases with age. We also find evidence of disk evolution (i.e., grain growth and significant dust settling) in all four regions, indicating that planet formation and disk evolution may begin to occur at earlier stages. We generally find these disks contain too little mass to form planetary companions, though we cannot rule out that planet formation may have already occurred. Finally, we examine the disk mass -host mass relationship and find that BD disks are largely consistent with previously-determined relationships for disks around T Tauri stars.

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Section: Discussionmentioning

confidence: 99%

Disk Masses and Dust Evolution of Protoplanetary Disks Around Brown Dwarfs

Rilinger,

Espaillat

2021

Preprint

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“…We have explored models with even higher ζ H 2 0 , and find that when ζ H 2 0 is above 2-3×10 −16 s −1 , η AD and η H becomes comparable to that of the MRN models, so that disc formation is strongly suppressed in such axisymmetric set-ups. Note that the conditions of ζ H 2 0 for disc formation is slightly more stringent if Hall effect is excluded, with a threshold of a few 10 −17 s −1 derived in Zhao et al (2016, see also Kuffmeier et al 2020).…”

Section: High Cosmic-ray Ionization Rate: Reduced Ion-neutral Drift A...mentioning

confidence: 94%

The Interplay between Ambipolar Diffusion and Hall Effect on Magnetic Field Decoupling and Protostellar Disc Formation

Zhao,

Caselli,

et al. 2020

Preprint

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Non-ideal MHD effects have been shown recently as a robust mechanism of averting the magnetic braking "catastrophe" and promoting protostellar disc formation. However, the magnetic diffusivities that determine the efficiency of non-ideal MHD effects are highly sensitive to microphysics. We carry out non-ideal MHD simulations to explore the role of microphysics on disc formation and the interplay between ambipolar diffusion (AD) and Hall effect during the protostellar collapse. We find that removing the smallest grain population ( 10 nm) from the standard MRN size distribution is sufficient for enabling disc formation. Further varying the grain sizes can result in either a Hall-dominated or an AD-dominated collapse; both form discs of tens of AU in size regardless of the magnetic field polarity. The direction of disc rotation is bimodal in the Hall dominated collapse but unimodal in the AD-dominated collapse. We also find that AD and Hall effect can operate either with or against each other in both radial and azimuthal directions, yet the combined effect of AD and Hall is to move the magnetic field radially outward relative to the infalling envelope matter. In addition, microphysics and magnetic field polarity can leave profound imprints both on observables (e.g., outflow morphology, disc to stellar mass ratio) and on the magnetic field characteristics of protoplanetary discs. Including Hall effect relaxes the requirements on microphysics for disc formation, so that prestellar cores with cosmic-ray ionization rate of 2-3×10 −16 s −1 can still form small discs of 10 AU radius. We conclude that disc formation should be relatively common for typical prestellar core conditions, and that microphysics in the protostellar envelope is essential to not only disc formation, but also protoplanetary disc evolution.

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“…Thus, the absence of a clear dependence of the disk radii on the initial turbulence, misalignment, and magnetic field strengths on the core scale in our results is consistent with the expectation from these non-ideal MHD simulations, and could support that the nonideal MHD effects play a more important role in disk formation compared to other parameters, like turbulence, mis-alignment, and magnetic field strengths. In this case, the disk radii could more depend on the magnetic diffusivities of the non-ideal MHD effects, which are related to cosmicray ionization rates and grain size distributions in protostellar sources (Padovani et al 2014;Zhao et al 2016Zhao et al , 2018Dzyurkevich et al 2017;Koga et al 2019;Kuffmeier et al 2020;Tsukamoto et al 2020). Nevertheless, turbulence and misalignment could still prompt angular momentum transfer from large to small scales in protostellar sources.…”

Section: Effects Of Turbulence and Magnetic Fieldmentioning

confidence: 99%

No impact of core-scale magnetic field, turbulence, or velocity gradient on sizes of protostellar disks in Orion A

Yen,

Zhao,

Koch

et al. 2021

Preprint

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We compared the sizes and fluxes of a sample of protostellar disks in Orion A measured with the ALMA 0.87 mm continuum data from the VANDAM survey with the physical properties of their ambient environments on the core scale of 0.6 pc estimated with the GBT GAS NH 3 and JCMT SCUPOL polarimetric data. We did not find any significant dependence of the disk radii and continuum fluxes on a single parameter on the core scale, such as the non-thermal line width, magnetic field orientation and strength, or magnitude and orientation of the velocity gradient. Among these parameters, we only found a positive correlation between the magnitude of the velocity gradient and the non-thermal line width. Thus, the observed velocity gradients are more likely related to turbulent motion but not large-scale rotation. Our results of no clear dependence of the disk radii on these parameters are more consistent with the expectation from non-ideal MHD simulations of disk formation in collapsing cores, where the disk size is self-regulated by magnetic braking and diffusion, compared to other simulations which only include turbulence and/or a magnetic field misaligned with the rotational axis. Therefore, our results could hint that the non-ideal MHD effects play a more important role in the disk formation. Nevertheless, we cannot exclude the influences on the observed disk size distribution by dynamical interaction in a stellar cluster or amounts of angular momentum on the core scale, which cannot be probed with the current data.

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Ionization: a possible explanation for the difference of mean disk sizes in star-forming regions

Cited by 42 publications

References 100 publications

Disk Masses and Dust Evolution of Protoplanetary Disks Around Brown Dwarfs

Disk Masses and Dust Evolution of Protoplanetary Disks Around Brown Dwarfs

The Interplay between Ambipolar Diffusion and Hall Effect on Magnetic Field Decoupling and Protostellar Disc Formation

No impact of core-scale magnetic field, turbulence, or velocity gradient on sizes of protostellar disks in Orion A

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