Thermochemical modelling of brown dwarf discs

Greenwood, Aaron; Kamp, I.; Waters, L. B. F. M.; Woitke, P.; Rab, Ch.; Aresu, G.; Spaans, Marco

doi:10.1051/0004-6361/201629389

Cited by 13 publications

(14 citation statements)

References 65 publications

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“…On the contrary, for compact disk models 13 CO does not scale linearly with mass, even for the lower mass disk models. This is in line with the findings of Boneberg et al (2018) and Greenwood et al (2017), who, using thermochemical modelling of Brown Dwarfs (BDs) disks, show that CO observations of compact disks are insensitive to disk mass due to high optical depths. One would therefore need optically thinner tracers, such as C 18 O, to trace disk masses.…”

Section: Resultssupporting

confidence: 91%

Compact Disks: an explanation to faint CO emission in Lupus disks

Miotello,

Rosotti,

Ansdell

et al. 2021

Preprint

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Context. ALMA disk surveys have shown that a large fraction of observed protoplanetary disks in nearby Star-Forming Regions (SFRs) are fainter than expected in CO isotopologue emission. Disks not detected in 13 CO line emission are also faint and often unresolved in the continuum emission at an angular resolution of around 0.2 arcseconds. Aims. Focusing on the Lupus SFR, the aim of this work is to investigate whether this population comprises radially extended and low mass disks -as commonly assumed so far -or if it is of intrinsically radially compact disks, an interpretation that we propose in this paper. The latter scenario was already proposed for individual sources or small samples of disks, while this work targets a large population of disks in a single young SFR for which statistical arguments can be made. Methods. A new grid of physical-chemical models of compact disks has been run with the physical-chemical code DALI in order to cover a region of the parameter space that had not been explored before with this code. Such models have been compared with 12 CO and 13 CO ALMA observations of faint disks in the Lupus SFR. The simulated integrated continuum and CO isotopologue fluxes of the new grid of compact models are reported. Results. Lupus disks that are not detected in 13 CO emission and with faint or undetected 12 CO emission are consistent with compact disk models. For disks with a limited radial extent, the emission of CO isotopologues is mostly optically thick and it scales with the surface area: i.e., it is fainter for smaller objects. The fraction of compact disks is potentially between roughly 50% and 60% of the entire Lupus sample. Deeper observations of 12 CO and 13 CO at a moderate angular resolution will allow us to distinguish whether faint disks are intrinsically compact, or if they are extended but faint, without the need of resolving them. If the fainter end of the disk population observed by ALMA disk surveys is consistent with such objects being very compact, this will either create a tension with viscous spreading or require MHD winds or external processes to truncate the disks.

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Section: Resultssupporting

confidence: 91%

Compact Disks: an explanation to faint CO emission in Lupus disks

Miotello,

Rosotti,

Ansdell

et al. 2021

Preprint

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“…The CO gas observations are a better tracer of disk size than continuum observations, as in the (sub)mm the dust is less optically thick than the 12 CO line. Assuming that the temperature structure of the CPD is known reasonably well, this is even possible if the gas disk is not spatially resolved, as the flux of optically thick line emission scales with the size of the emitting area (see also Greenwood et al (2017) for brown-dwarf disks).…”

Section: Companion and Disk Propertiesmentioning

confidence: 99%

Observing the gas component of circumplanetary disks around wide-orbit planet-mass companions in the (sub)mm regime

Rab

Kamp

Ginski

et al. 2019

A&A

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Context. Several detections of wide-orbit planet-mass/substellar companions around young solar-like stars were reported in the last decade. The origin of those possible planets is still unclear, but accretion tracers and VLT/SPHERE observations indicate that they are surrounded by circumplanetary material or even a circumplanetary disk (CPD). Aims. We want to investigate if the gas component of disks around wide-orbit companions is detectable with current (ALMA) and future (ngVLA) (sub)mm telescopes and what constraints such gas observations can provide on the nature of the circumplanetary material and the mass of the companion. Methods. We applied the radiation thermochemical disk code PRODIMO to model the dust and gas component of passive CPDs and produced realistic synthetic observables. We considered different companion properties (mass, luminosity), disk parameters (mass, size, dust properties) and radiative environments (background fields) and compared the resulting synthetic observables to telescope sensitivities and existing dust observations. Results. The main criterion for a successful detection is the size of the CPD. At a distance of about 150 pc, a CPD with an outer radius of about 10 au is detectable with ALMA in about six hours in optically thick CO lines. Other aspects, such as the luminosity, disk inclination, and background radiation fields of the companion, are also relevant and should be considered to optimize the observing strategy for detection experiments.Conclusions. For most of the known wide-orbit planet-mass companions, their maximum theoretical disk size of one-third of the Hill radius would be sufficient to allow detection of CO lines. It is therefore feasible to detect their gas disks and constrain the mass of the companion through the kinematic signature. Even in the case of non-detections such observations provide stringent constraints on disk size and gas mass, and this information is crucial for formation theories.

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“…They find that from millimetre spectral indices, large grains actually seem to be present in these discs. Greenwood et al (2017) have recently performed thermochemical modelling of BD discs including predictions for future ALMA observations of molecular tracers such as CO, HCN and HCO + . Their models suggest that BD discs are similar to T Tauri discs and that similar (thermochemical) diagnostics can be used.…”

Section: Introductionmentioning

confidence: 99%

The extremely truncated circumstellar disc of V410 X-ray 1: a precursor to TRAPPIST-1?

Boneberg

Facchini

Clarke

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Protoplanetary discs around brown dwarfs and very low mass stars offer some of the best prospects for forming Earth-sized planets in their habitable zones. To this end, we study the nature of the disc around the very low mass star V410 X-ray 1, whose SED is indicative of an optically thick and very truncated dust disc, with our modelling suggesting an outer radius of only 0.6 au. We investigate two scenarios that could lead to such a truncation, and find that the observed SED is compatible with both. The first scenario involves the truncation of both the dust and gas in the disc, perhaps due to a previous dynamical interaction or the presence of an undetected companion. The second scenario involves the fact that a radial location of 0.6 au is close to the expected location of the H 2 O snowline in the disc. As such, a combination of efficient dust growth, radial migration, and subsequent fragmentation within the snowline leads to an optically thick inner dust disc and larger, optically thin outer dust disc. We find that a firm measurement of the CO J = 2-1 line flux would enable us to distinguish between these two scenarios, by enabling a measurement of the radial extent of gas in the disc. Many models we consider contain at least several Earth-masses of dust interior to 0.6 au, suggesting that V410 X-ray 1 could be a precursor to a system with tightly-packed inner planets, such as TRAPPIST-1.

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Thermochemical modelling of brown dwarf discs

Cited by 13 publications

References 65 publications

Compact Disks: an explanation to faint CO emission in Lupus disks

Compact Disks: an explanation to faint CO emission in Lupus disks

Observing the gas component of circumplanetary disks around wide-orbit planet-mass companions in the (sub)mm regime

The extremely truncated circumstellar disc of V410 X-ray 1: a precursor to TRAPPIST-1?

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