The formation of brown dwarfs

Whitworth, Anthony Peter; Goodwin, S. P.

doi:10.1002/asna.200510447

Cited by 10 publications

(12 citation statements)

References 39 publications

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“…In recent years there has been a particular emphasis on building a solid comprehension of the mechanisms by which very low‐mass stars, brown dwarfs and free‐floating planetary mass objects form (e.g. Boss 2001; Bate 2004; Goodwin, Whitworth & Ward‐Thompson 2004; Whitworth & Goodwin 2005). Nevertheless, one key question which remains unanswered is what is the lowest possible mass of object that can be manufactured by the star formation process?…”

Section: Introductionmentioning

confidence: 99%

Proper motion L and T dwarf candidate members of the Pleiades

Casewell¹,

Dobbie²,

Hodgkin³

et al. 2007

Monthly Notices of the Royal Astronomical Society

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We present the results of a deep optical-near-infrared multi-epoch survey covering 2.5 square degrees of the Pleiades open star cluster to search for new very-low-mass brown dwarf members. A significant (~ 5 year) epoch difference exists between the optical (CFH12k I-, Z-band) and near infrared (UKIRT WFCAM J-band) observations. We construct I,I-Z and Z,Z-J colour magnitude diagrams to select candidate cluster members. Proper motions are computed for all candidate members and compared to the background field objects to further refine the sample. We recover all known cluster members within the area of our survey. In addition, we have discovered 9 new candidate brown dwarf cluster members. The 7 faintest candidates have red Z-J colours and show blue near-infrared colours. These are consistent with being L and T-type Pleiads. Theoretical models predict their masses to be around 11 Jupiter masses. There is 1 errata for this paperComment: 12 pages, 9 figures, 4 tables, accepted for publication in MNRAS Errata: 1 tabl

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Section: Introductionmentioning

confidence: 99%

Proper motion L and T dwarf candidate members of the Pleiades

Casewell¹,

Dobbie²,

Hodgkin³

et al. 2007

Monthly Notices of the Royal Astronomical Society

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“…The formation of BDs is a matter of considerable dispute. They might have formed in the same way as (low-mass) stars from turbulent cloud fragmentation (Elmegreen 1999;Whitworth & Goodwin 2005;André et al 2012), which would imply a continuous extension of the IMF into the sub-stellar regime. On the other hand, BDs might form e.g.…”

Section: Introductionmentioning

confidence: 99%

Deep Near-Ir Observations of the Globular Cluster M4: Hunting for Brown Dwarfs

Dieball

Bedin

Knigge

et al. 2016

ApJ

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We present an analysis of deep HST/WFC3 near-IR (NIR) imaging data of the globular cluster M 4. The best-photometry NIR colour-magnitude diagram (CMD) clearly shows the main sequence extending towards the expected end of the Hydrogen-burning limit and going beyond this point towards fainter sources. The white dwarf sequence can be identified. As such, this is the deepest NIR CMD of a globular cluster to date. Archival HST optical data were used for proper-motion cleaning of the CMD and for distinguishing the white dwarfs (WDs) from brown dwarf (BD) candidates. Detection limits in the NIR are around F 110W ≈ 26.5 mag and F 160W ≈ 27 mag, and in the optical around F 775W ≈ 28 mag. Comparing our observed CMDs with theoretical models, we conclude that we have reached beyond the H-burning limit in our NIR CMD and are probably just above or around this limit in our optical-NIR CMDs. Thus, any faint NIR sources that have no optical counterpart are potential BD candidates, since the optical data are not deep enough to detect them. We visually inspected the positions of NIR sources which are fainter than the H-burning limit in F 110W and for which the optical photometry did not return a counterpart. We found in total five sources for which we did not get an optical measurement. For four of these five sources, a faint optical counterpart could be visually identified, and an upper optical magnitude was estimated. Based on these upper optical magnitude limits, we conclude that one source is likely a WD, one source could either be a WD or BD candidate, and the remaining two sources agree with being BD candidates. For only one source no optical counterpart could be detected, which makes this source a good BD candidate. We conclude that we found in total four good BD candidates.

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“…There are at least four different formation mechanisms that have been suggested, such as formation through the "ejection" of pre-stellar cores (Reipurth & Clarke 2001;Bate, Bonnell & Bromm 2002;Delgado-Donate, Clarke & Bate 2003;Sterzik et al 2003) or through "turbulence", or turbulent fragmentation (Padoan & Nordlund 2002;Padoan & Nordlund 2004). Other theories include that of "disc fragmentation", forming sub-stellar cores from an initially massive pre-stellar core via fragmentation of a large circumstellar disk (Boffin et al 1998;Bate, Bonnell & Bromm 2003;Whitworth & Goodwin 2005;Whitworth & Stamatellos 2006) and "photo-erosion", where sub-stellar objects form in the presence of a higher mass star embedded in a HII region (Whitworth & Zinnecker 2004). As the formation mechanisms could indeed be different for sub-stellar objects it is thus important to define the mass function and formation history in the sub-stellar regime if we wish to fully understand their contribution to the Galactic population.…”

Section: Introductionmentioning

confidence: 99%

The sub-stellar birth rate from UKIDSS★

Day-Jones

Marocco

Pinfield

et al. 2013

Monthly Notices of the Royal Astronomical Society

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We present a new sample of mid L to mid T dwarfs with effective temperatures of 1100 to 1700 K selected from the UKIDSS Large Area Survey and confirmed with infrared spectra from X-Shooter/VLT. This effective temperature range is especially sensitive to the formation history of Galactic brown dwarfs and allows us to constrain the form of the sub-stellar birth rate, with sensitivity to differentiate between a flat (stellar like) birth rate, and an exponentially declining form. We present the discovery of 63 new L and T dwarfs from the UKIDSS LAS DR7, including the identification of 12 likely unresolved binaries, which form the first complete sub-set from our program, covering 495 sq degrees of sky, complete to J=18.1. We compare our results for this sub-sample with simulations of differing birth rates for objects of mass 0.10-0.03M ⊙ and ages 1-10Gyrs. We find that the more extreme birth rates (e.g. a halo type form) can likely be excluded as the true form of the birth rate. In addition we find that although there is substantial scatter we find a preference for a mass function, with a power-law index, α in the range −1 < α < 0 that is consistent (within the errors) with the studies of late T dwarfs.

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The formation of brown dwarfs

Cited by 10 publications

References 39 publications

Proper motion L and T dwarf candidate members of the Pleiades

Proper motion L and T dwarf candidate members of the Pleiades

Deep Near-Ir Observations of the Globular Cluster M4: Hunting for Brown Dwarfs

The sub-stellar birth rate from UKIDSS★

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