The formation of brown dwarfs

Whitworth, A. P.; Stamatellos, Dimitris; Walch, Stefanie; Duffard, R.; Goodwin, S. P.; Hubber, D. A.; Parker, R. J.

doi:10.1017/s174392130999113x

Cited by 9 publications

(9 citation statements)

References 131 publications

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“…In the cool outer parts of the disc, the Rosseland mean opacity is related to temperature by κ ∝ T 2 (Whitworth et al 2010). Therefore our cooling rate now has a dependence Λ ∝ T 2 .…”

Section: Basic Modelmentioning

confidence: 99%

Directly observing continuum emission from self-gravitating spiral waves

Hall

Forgan

Rice

et al. 2016

Mon. Not. R. Astron. Soc.

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We use a simple, self-consistent, self-gravitating semi-analytic disc model to conduct an examination of the parameter space in which self-gravitating discs may exist. We then use Monte-Carlo radiative transfer to generate synthetic ALMA images of these self-gravitating discs to determine the subset of this parameter space in which they generate non-axisymmetric structure that is potentially detectable by ALMA. Recently, several transition discs have been observed to have non-axisymmetric structure that extends out to large radii. It has been suggested that one possible origin of these asymmetries could be spiral density waves induced by disc self-gravity. We use our simple model to see if these discs exist in the region of parameter space where self-gravity could feasibly explain these spiral features. We find that for self-gravity to play a role in these systems typically requires a disc mass around an order of magnitude higher than the observed disc masses for the systems. The spiral amplitudes produced by self-gravity in the local approximation are relatively weak when compared to amplitudes produced by tidal interactions, or spirals launched at Lindblad resonances due to embedded planets in the disc. As such, we ultimately caution against diagnosing spiral features as being due to self-gravity, unless the disc exists in the very narrow region of parameter space where the spiral wave amplitudes are large enough to produce detectable features, but not so large as to cause the disc to fragment.

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Section: Basic Modelmentioning

confidence: 99%

Directly observing continuum emission from self-gravitating spiral waves

Hall

Forgan

Rice

et al. 2016

Mon. Not. R. Astron. Soc.

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“…both at lower masses (below 40 M Jup ) and in spatial content, frequently focusing on the inner regions of clusters. It is therefore unknown whether, as one moves to lower masses, other formation mechanisms take over (e.g., Whitworth et al 2010). At the same time, the increasing capacity of numerical simulations to reproduce the collapse of entire molecular clouds is such that the comparison between simulations and observations starts to be hampered by our empirical knowledge based on small number statistics of the low-mass end of the brown dwarf regime (e.g., Bate 2009).…”

Section: Introductionmentioning

confidence: 99%

Spectroscopy of new brown dwarf members ofρ Ophiuchi and an updated initial mass function

Oliveira¹,

Moraux²,

Bouvier³

et al. 2012

A&A

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Aims. To investigate the universality hypothesis of the initial mass function in the substellar regime, the population of the ρ Ophiuchi molecular cloud is analysed by including a new sample of low-mass spectroscopically confirmed members. To that end, we have conducted a large spectroscopic follow-up of young substellar candidates uncovered in our previous photometric survey. Methods. The spectral types and extinction were derived for a newly found population of substellar objects, and its masses estimated by comparison to evolutionary models. A thoroughly literature search was conducted to provide an up-to-date census of the cluster, which was then used to derive the luminosity and mass functions, as well as the ratio of brown dwarfs to stars in the cluster. These results were then compared to other young clusters. Results. It is shown that the study of the substellar population of the ρ Ophiuchi molecular cloud is hampered only by the high extinction in the cluster ruling out an apparent paucity of brown dwarfs. The discovery of 16 new members of ρ Ophiuchi, 13 of them in the substellar regime, reveals the low-mass end of its population and shows the success of our photometric candidate selection with the WIRCam survey. The study of the brown dwarf population of the cluster reveals a high disk fraction of 76 +5 −8 %. Conclusions. Taking the characteristic peak mass of the derived mass function and the ratio of brown dwarfs to stars into account, we conclude that the mass function of ρ Ophiuchi is similar to other nearby young clusters.

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“…The various scenarios for the formation of very low mass objects have been recently reviewed by Whitworth et al (2007) in Protostars and Planets V, and we refer to that paper for a comprehensive discussion and references. As we have already mentioned, it is possible that brown dwarfs form in similar fashion to their more massive counterparts, if fragmentation of molecular clouds produces gravitationally unstable very low mass cores.…”

Section: The Formation Of Very Low Mass Objectsmentioning

confidence: 99%

“…Gravitational collapse of molecular cores is possible for cores of mass as low as ∼1-5 Jupiter masses (opacity limit; e.g., Whitworth et al (2007), provided that such cores are produced in molecular clouds and are gravitationally unstable. So far, it has been very difficult to identify and study very low mass cores, and a number of alternative scenarios for the formation of brown dwarfs have been proposed (Sect.…”

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confidence: 99%

The study of young substellar objects with ALMA

Natta

Testi

2007

Astrophys Space Sci

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We discuss the potential of ALMA for studying the formation of substellar objects. We first review briefly the various formation mechanisms proposed so far and stress the unique capability of ALMA to detect and study prebrown dwarf cores and to confirm the core-collapse scenario to the lowest possible masses. We then discuss the properties of disks around substellar objects. We show how it will be possible to detect with ALMA most disks around objects with mass as low as few Jupiter masses, and to resolve spatially their emission in the more favorable cases.

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The formation of brown dwarfs

Cited by 9 publications

References 131 publications

Directly observing continuum emission from self-gravitating spiral waves

Directly observing continuum emission from self-gravitating spiral waves

Spectroscopy of new brown dwarf members ofρ Ophiuchi and an updated initial mass function

The study of young substellar objects with ALMA

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